@article{woolard_trew_polla_stroscio_varshney_jensen_jensen_lugli_aono_2008, title={Nanosensors for defense and security}, volume={8}, ISSN={["1530-437X"]}, DOI={10.1109/jsen.2008.924436}, abstractNote={The 59 articles in this special issue focus on nanosensors for defense and security.}, number={5-6}, journal={IEEE SENSORS JOURNAL}, author={Woolard, Dwight L. and Trew, Robert J. and Polla, Dennis L. and Stroscio, Michael A. and Varshney, Usha and Jensen, Janet and Jensen, James O. and Lugli, Paolo O. and Aono, Masakazu}, year={2008}, pages={641–646} }
 @article{komirenko_kim_kochelap_koroteev_stroscio_2003, title={Nonlinear regimes of coherent optical phonon generation in quantum wells under electric current pumping}, volume={68}, ISSN={0163-1829 1095-3795}, url={http://dx.doi.org/10.1103/PhysRevB.68.155308}, DOI={10.1103/physrevb.68.155308}, abstractNote={We present an analysis of nonlinear regimes of the coherent optical phonon generation under the electron drift in quantum wells. The phonon and electron subsystems are treated self-consistently. This allows us to find thesteady-state generation regimes with macroscopic populations of optical phonon modes and the electron transport controlled in part by the generated phonons. The generation regimes demonstrate a pronounced threshold character. At high electric fields above the threshold, practically single-mode generation occurs and the current-voltage characteristic is considerably changed. We demonstrate high efficiency generation of the coherent optical phonons by the electric current. The coherent macroscopic optical displacements and the amplitudes of oscillating electrostatic fields are evaluated. The proposed model based on the electron nonlinearities predicts a range of the pumping electric fields under which the steady state phonon generation is realized. Our results suggest that the phonon avalanche occurs beyond this field range.}, number={15}, journal={Physical Review B}, publisher={American Physical Society (APS)}, author={Komirenko, S. M. and Kim, K. W. and Kochelap, V. A. and Koroteev, V. V. and Stroscio, M. A.}, year={2003}, month={Oct} }
 @article{komirenko_kim_demidenko_kochelap_stroscio_2001, title={Amplification of transverse acoustic phonons in quantum well heterostructures with piezoelectric interaction}, volume={90}, ISSN={0021-8979 1089-7550}, url={http://dx.doi.org/10.1063/1.1402145}, DOI={10.1063/1.1402145}, abstractNote={We have analyzed amplification of transverse phonons confined in quantum well (QW) heterostructures through piezoelectric electron–phonon interaction with drifting electrons. It was found that this mechanism of interaction couples the low-dimensional electrons and the shear-horizontal (SH) confined phonons. We have studied the electrostatic potential accompanying the SH waves and found that efficient interaction can be achieved for the lowest antisymmetric SH phonon branch in a narrow band of phonon frequencies. For AlGaAs QWs the amplification coefficient was calculated to be on the order of 100 cm−1 in the sub-THz phonon frequency range. These results suggest an electrical method for coherent phonon generation in the technologically well-developed AlGaAs QW heterostructures.}, number={8}, journal={Journal of Applied Physics}, publisher={AIP Publishing}, author={Komirenko, S. M. and Kim, K. W. and Demidenko, A. A. and Kochelap, V. A. and Stroscio, M. A.}, year={2001}, month={Oct}, pages={3934–3941} }
 @article{komirenko_kim_stroscio_dutta_2001, title={Applicability of the Fermi golden rule and the possibility of low-field runaway transport in nitrides}, volume={13}, ISSN={0953-8984 1361-648X}, url={http://dx.doi.org/10.1088/0953-8984/13/28/306}, DOI={10.1088/0953-8984/13/28/306}, abstractNote={We investigated electron transport characteristics of wide-band polar semi-conductors with intermediate strength of the electron–phonon interaction. Electron energy loss to the lattice was calculated as a function of electron velocity for various materials in the frameworks of (a) a perturbative approach based on the calculation of scattering rates from Fermi's golden rule and (b) a non-perturbative approach based on the path-integral formalism of Thornber and Feynman. Our results suggest that the standard perturbative treatment can be applied to GaN and AlN despite the relatively strong electron–phonon coupling in this material system, with intercollision times of the order of the period of the phonon oscillation. Our findings also indicate the possibility for unique long-distance runaway transport in nitrides which may occur at the pre-threshold electric fields. The polaron ground-state energy and effective masses are calculated for GaN and AlN as well as for GaAs and Al2O3. An expression for the Fröhlich coupling constant for wurtzites is derived.}, number={28}, journal={Journal of Physics: Condensed Matter}, publisher={IOP Publishing}, author={Komirenko, S M and Kim, K W and Stroscio, M A and Dutta, M}, year={2001}, month={Jun}, pages={6233–6246} }
 @article{stroscio_dutta_kahn_kim_2001, title={Continuum model of optical phonons in a nanotube}, volume={29}, ISSN={0749-6036}, url={http://dx.doi.org/10.1006/spmi.2001.0980}, DOI={10.1006/spmi.2001.0980}, abstractNote={The properties of nanotubes are of intense current interest due, in part, to the discovery of the carbon nanotube. In this paper, the optical phonons are modeled for a nanotube by treating the nanotube as a continuum medium. A quantization prescription is applied to facilitate the first determination of the quantum-mechanical normalizations of selected optical phonon modes. It is shown that normalization of the lowest azimuthal mode may be determined analytically. The deformation potentials describing carrier optical-phonon scattering are readily determined from these normalized continuum modes.}, number={6}, journal={Superlattices and Microstructures}, publisher={Elsevier BV}, author={Stroscio, Michael A. and Dutta, Mitra and Kahn, Daniel and Kim, Ki Wook}, year={2001}, month={Jun}, pages={405–409} }
 @article{komirenko_kim_kochelap_fedorov_stroscio_2001, title={Generation of coherent confined LO phonons under the drift of two-dimensional electrons}, volume={63}, ISSN={0163-1829 1095-3795}, url={http://dx.doi.org/10.1103/PhysRevB.63.165308}, DOI={10.1103/physrevb.63.165308}, abstractNote={This paper addresses the effect of generation of confined LO phonons by drifting electrons in quantum wells. We have obtained a general formula for the phonon increment as a function of the phonon wave vector, the electron drift velocity, and parameters of the structure. The kinetic parameters of the drifting electrons are estimated by using momentum and energy balance equations for electron scattering by the confined optical phonons. We have performed numerical estimates of the phonon increment, as well as the phonon lifetimes, and found that AlAs/GaAs/AlAs and GaSb/InSb/GaSb quantum well structures with high drift velocities can demonstrate the effect of generation of the coherent confined optical modes. Essentially, the phonon increment has a maximum as a function of the wave vector. This implies a strong selection of the generated phonon modes. We briefly discuss the nonlinear electron mechanism which stabilizes the increase of the phonon populations and provides for the steady-state phonon generation.}, number={16}, journal={Physical Review B}, publisher={American Physical Society (APS)}, author={Komirenko, S. M. and Kim, K. W. and Kochelap, V. A. and Fedorov, I. and Stroscio, M. A.}, year={2001}, month={Apr} }
 @article{komirenko_kim_kochelap_stroscio_2001, title={High-field electron transport in nanoscale group-III nitride devices}, volume={228}, ISSN={["0370-1972"]}, DOI={10.1002/1521-3951(200111)228:2<593::aid-pssb593>3.0.co;2-2}, abstractNote={Focusing on the short-size group-III nitride heterostructures, we have developed a model which takes into account main features of transport of electrons injected into a polar semiconductor under high electric fields. The model is based on an exact analytical solution of Boltzmann transport equation. The electron velocity distribution over the device is analyzed at different fields and the basic characteristics of the high-field electron transport are obtained. The critical field for the runaway regime, when electron energies and velocities increase with distance which results in the average velocities higher than the peak velocity in bulk-like samples, is determined. We have found that the runaway electrons are characterized by a distribution function with population inversion. Different nitride-based small-size devices where this effect can have an impact on the device performance are considered.}, number={2}, journal={PHYSICA STATUS SOLIDI B-BASIC RESEARCH}, author={Komirenko, SM and Kim, KW and Kochelap, VA and Stroscio, MA}, year={2001}, month={Nov}, pages={593–597} }
 @article{dutta_alexson_bergman_nemanich_dupuis_kim_komirenko_stroscio_2001, title={Phonons in III–V nitrides: Confined phonons and interface phonons}, volume={11}, ISSN={1386-9477}, url={http://dx.doi.org/10.1016/S1386-9477(01)00217-X}, DOI={10.1016/S1386-9477(01)00217-X}, abstractNote={Phonons in III–V nitrides are examined experimentally for dimensionally confined systems and for alloys of InGaN with a view towards understanding the phonon modes of these systems. Results are compared with the predictions of Loudon's model for uniaxial semiconductors. The modes of the InGaN system are compared with those of the AlGaN ternary alloy. The first Raman measurements of interface phonons in binary GaN–AlN superlattices are presented.}, number={2-3}, journal={Physica E: Low-dimensional Systems and Nanostructures}, publisher={Elsevier BV}, author={Dutta, M and Alexson, D and Bergman, L and Nemanich, R.J and Dupuis, R and Kim, K.W and Komirenko, S and Stroscio, M}, year={2001}, month={Oct}, pages={277–280} }
 @article{kahn_kim_stroscio_2001, title={Quantized vibrational modes of nanospheres and nanotubes in the elastic continuum model}, volume={89}, ISSN={0021-8979 1089-7550}, url={http://dx.doi.org/10.1063/1.1356429}, DOI={10.1063/1.1356429}, abstractNote={The properties of nanoscale spheres and tubes are of recent interest due to the discovery of the fullerene molecule and the carbon nanotube. These carbon structures can be modeled as nanoscale spherical or cylindrical shells. In this article, these nanostructures are treated in the thin shell approximation with the elastic properties taken to be those of the graphene sheet. A quantization prescription is applied to the classical elastic modes to facilitate the first calculations of the quantum-mechanical normalizations of selected modes. These modes are shown to be amenable to the study of electron-phonon interactions. Indeed, electron-phonon interaction Hamiltonians are derived. Moreover, it is shown for such a tube of finite length that the electron-phonon interaction strength depends on the axial position. As a special case it is shown that the dispersion relation for the clamped tube depends on the length of the tube. In this article we consider both the vibrational frequencies and the mode quantization for both spherical shell and the nanotube using realistic material parameters.}, number={9}, journal={Journal of Applied Physics}, publisher={AIP Publishing}, author={Kahn, Daniel and Kim, K. W. and Stroscio, Michael A.}, year={2001}, month={May}, pages={5107–5111} }
 @article{komirenko_kim_kochelap_stroscio_2001, title={Runaway effects in nanoscale group-III nitride semiconductor structures}, volume={64}, ISSN={0163-1829 1095-3795}, url={http://dx.doi.org/10.1103/PhysRevB.64.113207}, DOI={10.1103/physrevb.64.113207}, abstractNote={We have revisited the problem of electron runaway in strong electric fields in polar semiconductors focusing on nanoscale group-III nitride structures. By developing a transport model that accounts for the main features of electrons injected in short devices under high electric fields, we have investigated the electron distribution as a function of electron momenta and coordinates. Runaway transport is analyzed in detail. The critical field of this regime is determined for InN, GaN, and AlN. We found that the transport in the nitrides is always dissipative (i.e., no ballistic transport). For the runaway regime, however, the electrons increase their velocities with distance, which results in average velocities higher than the peak velocity in bulklike samples. We have demonstrated that the runaway electrons are characterized by a distribution function exhibiting a population inversion.}, number={11}, journal={Physical Review B}, publisher={American Physical Society (APS)}, author={Komirenko, S. M. and Kim, K. W. and Kochelap, V. A. and Stroscio, M. A.}, year={2001}, month={Aug} }
 @article{alexson_bergman_nemanich_dutta_stroscio_parker_bedair_el-masry_adar_2001, title={Ultraviolet raman study of A(1)(LO) and E-2 phonons in InxGa1-xN alloys}, volume={89}, ISSN={["0021-8979"]}, DOI={10.1063/1.1330760}, abstractNote={We report on ultraviolet Raman spectroscopy of InxGa1−xN thin films grown on sapphire by metal-organic chemical vapor deposition. The A1(LO) and E2 phonon mode behavior was investigated over a large compositional range (0<x<0.50). Compelling evidence is presented for one-mode behavior for the A1(LO) phonon, and data suggestive of two-mode behavior are presented for the E2 phonon.}, number={1}, journal={JOURNAL OF APPLIED PHYSICS}, author={Alexson, D and Bergman, L and Nemanich, RJ and Dutta, M and Stroscio, MA and Parker, CA and Bedair, SM and El-Masry, NA and Adar, F}, year={2001}, month={Jan}, pages={798–800} }
 @article{komirenko_kim_demidenko_kochelap_stroscio_2000, title={Cerenkov generation of high-frequency confined acoustic phonons in quantum wells}, volume={76}, ISSN={0003-6951 1077-3118}, url={http://dx.doi.org/10.1063/1.126195}, DOI={10.1063/1.126195}, abstractNote={We analyze the Cerenkov emission of high-frequency confined acoustic phonons by drifting electrons in a quantum well. We find that the electron drift can cause strong phonon amplification (generation). A general formula for the gain coefficient α is obtained as a function of the phonon frequency and the structure parameters. The gain coefficient increases sharply in the short-wave region. For the example of a Si/SiGe/Si device, it is shown that the amplification coefficients of the order of hundreds of cm−1 can be achieved in the subterahertz frequency range.}, number={14}, journal={Applied Physics Letters}, publisher={AIP Publishing}, author={Komirenko, S. M. and Kim, K. W. and Demidenko, A. A. and Kochelap, V. A. and Stroscio, M. A.}, year={2000}, month={Apr}, pages={1869–1871} }
 @article{komirenko_kim_kochelap_fedorov_stroscio_2000, title={Coherent optical phonon generation by the electric current in quantum wells}, volume={77}, ISSN={0003-6951 1077-3118}, url={http://dx.doi.org/10.1063/1.1334653}, DOI={10.1063/1.1334653}, abstractNote={This letter addresses the effect of generation of confined LO phonons by drifting electrons in quantum wells. We have derived a general formula for the phonon increment as a function of phonon wave vector, electron drift velocity, and structure parameters. Numerical estimates of the phonon increment and the phonon lifetimes have shown that AlAs/GaAs/AlAs and GaSb/InSb/GaSb quantum well structures can demonstrate the effect of coherent LO phonon generation by the electric current.}, number={25}, journal={Applied Physics Letters}, publisher={AIP Publishing}, author={Komirenko, S. M. and Kim, K. W. and Kochelap, V. A. and Fedorov, I. and Stroscio, M. A.}, year={2000}, month={Dec}, pages={4178–4180} }
 @article{komirenko_kim_stroscio_dutta_2000, title={Energy-dependent electron scattering via interaction with optical phonons in wurtzite crystals and quantum wells}, volume={61}, ISSN={0163-1829 1095-3795}, url={http://dx.doi.org/10.1103/PhysRevB.61.2034}, DOI={10.1103/physrevb.61.2034}, abstractNote={A formalism for the calculation of the scattering rate in wurtzite-type crystals and quantum wells (QW's) is developed taking into account features of the optical phonon spectra in an optically anisotropic medium. The electron-scattering rate due to the interaction with infrared/Raman-active polar optical phonons in GaN, bulk material, and heterostructures, is investigated. To determine the dependence of scattering rate on optical anisotropy and dimensionally induced transformation of the phonon spectra, three cases are considered: (a) bulk material with different orientations of the electron wave vector with respect to the optical axis; (b) a system in which bulk phonons interact with electrons confined in a QW; and (c) free-standing and embedded QW's where the effects of confinement of both electron and phonon subsystems are taken into account. It is found that the scattering rate depends weakly on the initial orientation of the electron wave vector. Exceptions are the energy intervals which correspond to the threshold values for emission of both TO-like and LO-like bulk phonons. Our results reveal a complex and strong dependence of the electron-scattering rate on the dispersion of a particular mode. Moreover, this dependence is found to be the main factor which determines electron-phonon scattering in wurtzite heterostructures, in particular, through the relation between phonon phase and group velocities. For the optically anisotropic media considered, the effect of spatial localization of the phonon modes on the scattering rate is found to be as strong as the effect of electron confinement.}, number={3}, journal={Physical Review B}, publisher={American Physical Society (APS)}, author={Komirenko, S. M. and Kim, K. W. and Stroscio, M. A. and Dutta, M.}, year={2000}, month={Jan}, pages={2034–2040} }
 @article{komirenko_kim_demidenko_kochelap_stroscio_2000, title={Generation and amplification of sub-THz coherent acoustic phonons under the drift of two-dimensional electrons}, volume={62}, ISSN={0163-1829 1095-3795}, url={http://dx.doi.org/10.1103/PhysRevB.62.7459}, DOI={10.1103/physrevb.62.7459}, abstractNote={This paper addresses the \ifmmode \check{C}\else \v{C}\fi{}erenkov emission of high-frequency confined acoustic phonons by drifting electrons in a quantum well. We have found that the electron drift can cause strong phonon amplification (generation). The spectra of the confined modes are calculated and their confinement properties are analyzed. The spectra consist of a set of branches, and for each branch, the confinement effect increases considerably when the phonon wave vector increases. We have studied the coupling between electrons and confined modes and proved that the coupling is a nonmonotonous function of the wave vector for each of the phonon branches. We have obtained a general formula for the gain coefficient as a function of the phonon frequency and the structure parameters. For each of the branches, the amplification takes place in a spectrally separated and quite narrow amplification band in the high-frequency range. For the example of p-doped Si/SiGe/Si heterostructures it is shown that the amplification coefficients of the order of hundreds of ${\mathrm{cm}}^{\ensuremath{-}1}$ can be achieved in the sub-THz frequency range.}, number={11}, journal={Physical Review B}, publisher={American Physical Society (APS)}, author={Komirenko, S. M. and Kim, K. W. and Demidenko, A. A. and Kochelap, V. A. and Stroscio, M. A.}, year={2000}, month={Sep}, pages={7459–7469} }
 @article{bergman_dutta_stroscio_komirenko_nemanich_eiting_lambert_kwon_dupuis_2000, title={Photoluminescence and recombination mechanisms in GaN/Al0.2Ga0.8N superlattice}, volume={76}, ISSN={["0003-6951"]}, DOI={10.1063/1.126225}, abstractNote={A detailed study of photoluminescence (PL) of GaN(1 nm)/Al0.2Ga0.8N(3.3 nm) twenty periods superlattice grown via metal-organic chemical vapor deposition is presented. The dependence of the PL emission energy, linewidth, and intensity on temperature, in the low temperature regime, is consistent with recombination mechanisms involving bandtail states attributed to a small degree of interfacial disorder. The activation energy of the nonradiative centers in our superlattice agrees well with the value we derive for the width of the tail-state distribution. Moreover, we find that the average phonon energy of the phonons that control the interband PL energy at high temperatures is larger for the superlattice than for a high-quality GaN film. This observation is consistent with model calculations predicting the phonon mode properties of GaN–AlN-based wurtzite heterostructures.}, number={15}, journal={APPLIED PHYSICS LETTERS}, author={Bergman, L and Dutta, M and Stroscio, MA and Komirenko, SM and Nemanich, RJ and Eiting, CJ and Lambert, DJH and Kwon, HK and Dupuis, RD}, year={2000}, month={Apr}, pages={1969–1971} }
 @article{kiselev_kim_stroscio_2000, title={Thermal conductivity of Si/Ge superlattices: A realistic model with a diatomic unit cell}, volume={62}, ISSN={0163-1829 1095-3795}, url={http://dx.doi.org/10.1103/PhysRevB.62.6896}, DOI={10.1103/physrevb.62.6896}, abstractNote={This paper considers the effects of a realistic description of phonons in diamondlike semiconductors and their conversion on the abrupt heterointerfaces on the thermal conductivity of the superlattice (SL). Due to the much larger mass of Ge atoms in comparison to Si, the most probable acoustic phonons in Si layers at room temperature have no counterpart in Ge. In simplified models where Si and Ge are simulated by monatomic crystals with fitted parameters, this leads to the highly efficient trapping of high-energy acoustic phonons in Si layers and drastic reduction of the SL thermal conductivity. The proposed approach incorporates the optical branches and the effective conversion of the phonons at interfaces extends the temperature range for which the model is valid and thereby leads to corrections to predicted thermal conductivity.}, number={11}, journal={Physical Review B}, publisher={American Physical Society (APS)}, author={Kiselev, A. A. and Kim, K. W. and Stroscio, M. A.}, year={2000}, month={Sep}, pages={6896–6899} }
 @article{kiselev_kim_stroscio_1999, title={Calculational approach for the structure of electron and hole levels in quantum dots of varying shape}, volume={60}, ISSN={0163-1829 1095-3795}, url={http://dx.doi.org/10.1103/PhysRevB.60.7748}, DOI={10.1103/physrevb.60.7748}, abstractNote={Another approach to the calculation of electron and hole states in quantum dots is proposed. It benefits from the particular choice of products of powers of Cartesian coordinates as a basis, since it is possible to evaluate all required matrix elements analytically for these systems. A variety of dot shapes in the presence of external electric fields can be analyzed conveniently. This approach provides a way to calculate quantum dot ensemble averages quickly and effectively.}, number={11}, journal={Physical Review B}, publisher={American Physical Society (APS)}, author={Kiselev, A. A. and Kim, K. W. and Stroscio, M. A.}, year={1999}, month={Sep}, pages={7748–7751} }
 @article{kiselev_kim_stroscio_1999, title={Computing carrier interactions with confined and excluded phonons in nanostructures of complex geometries}, volume={59}, ISSN={0163-1829 1095-3795}, url={http://dx.doi.org/10.1103/PhysRevB.59.10212}, DOI={10.1103/physrevb.59.10212}, abstractNote={We provide a simple and highly effective procedure for calculating quantities such as electron scattering rates involving confined and excluded phonons for quantum wires of arbitrary geometry. This problem is particularly difficult to solve by the usual summation procedure as well as by alternative treatments proposed thus far. To demonstrate the strength of our approach, we produce exact analytical results in the case of a quantum well. As a numerical example, we consider a classic T-shaped structure with different sizes and radii of curvature at the intersections. We examine the possibility of manipulating structural characteristics such as electron-phonon scattering rates by making minor modifications to the quantum wire cross-sectional geometries.}, number={15}, journal={Physical Review B}, publisher={American Physical Society (APS)}, author={Kiselev, A. A. and Kim, K. W. and Stroscio, M. A.}, year={1999}, month={Apr}, pages={10212–10216} }
 @article{alexson_bergman_dutta_kim_komirenko_nemanich_lee_stroscio_yu_1999, title={Confined phonons and phonon-mode properties of III–V nitrides with wurtzite crystal structure}, volume={263-264}, ISSN={0921-4526}, url={http://dx.doi.org/10.1016/S0921-4526(98)01423-9}, DOI={10.1016/s0921-4526(98)01423-9}, abstractNote={Stimulated by the recent interest in the use of nitride-based III–V wurtzite structures for optoelectronic and electronic devices, this paper reports on the application of the Loudon model for uniaxial crystals to derive the Fröhlich interaction Hamiltonian as well as the electron–optical-phonon scattering rate in wurtzite crystals. This paper also presents experimental analyses of the mode behavior of phonons in wurtzite crystals.}, journal={Physica B: Condensed Matter}, publisher={Elsevier BV}, author={Alexson, D and Bergman, Leah and Dutta, Mitra and Kim, K.W and Komirenko, S and Nemanich, Robert J and Lee, B.C and Stroscio, Michael A and Yu, SeGi}, year={1999}, month={Mar}, pages={510–513} }
 @article{komirenko_kim_stroscio_dutta_1999, title={Dispersion of polar optical phonons in wurtzite quantum wells}, volume={59}, ISSN={0163-1829 1095-3795}, url={http://dx.doi.org/10.1103/PhysRevB.59.5013}, DOI={10.1103/physrevb.59.5013}, abstractNote={Dispersion relations for polar optical phonon modes in wurtzite quantum wells (QW's) are obtained in the framework of the dielectric continuum model. It is found that anisotropy of the dielectric medium causes a number of qualitative peculiarities in the phonon spectra. Among these are the absence of the proper confinement for the oscillatory waves located in the QW, inversion of the order of symmetric and antisymmetric quasiconfined optical modes, formation of the finite energy intervals where such confined modes---which are found to be dispersive---can exist, penetration of the half-space phonons into the QW, etc. Some additional peculiarities, such as appearance of propagating modes, strong dispersion of long-wavelength half-space modes, and reduction of the number of interface modes, arise as a result of overlapping characteristic phonon frequencies of the surrounding material and the material of QW. Predicted phonon behavior leads to the conclusion that dependence of dielectric properties of ternary-binary low-dimensional wurtzite heterostructures on composition can serve as a powerful tool for the purposes of phonon spectrum engineering. In order to illustrate these results, the optical phonon spectra are calculated for an ${\mathrm{Al}}_{0.15}{\mathrm{Ga}}_{0.85}\mathrm{N}/\mathrm{GaN}/{\mathrm{Al}}_{0.15}{\mathrm{Ga}}_{0.85}\mathrm{N} \mathrm{QW},$ an $\mathrm{AlN}/\mathrm{GaN}/\mathrm{AlN} \mathrm{QW},$ and for a $\mathrm{GaN}$ dielectric slab.}, number={7}, journal={Physical Review B}, publisher={American Physical Society (APS)}, author={Komirenko, S. M. and Kim, K. W. and Stroscio, M. A. and Dutta, M.}, year={1999}, month={Feb}, pages={5013–5020} }
 @article{komirenko_kim_kochelap_dutta_stroscio_1999, title={Phase instability and electron-assisted renormalization of acoustic phonon spectrum in free-standing quantum wires}, volume={263-264}, ISSN={0921-4526}, url={http://dx.doi.org/10.1016/S0921-4526(98)01253-8}, DOI={10.1016/s0921-4526(98)01253-8}, abstractNote={Abstract In this paper we consider the possibility of a Peierls phase transition for a system of one-dimensional electrons and acoustic phonons confined in a free-standing quantum wire (FSQWI). We assume that electrons and phonons are coupled via the deformation potential interaction. The dispersion relation for this system is derived taking into account the role of electrostatic effects. The Peierls phase transition to the state characterized by periodic lattice deformation (PLD) is obtained in the high-permittivity limit. The formalism developed in this paper facilitates investigation of the renormalized acoustic phonon spectrum and predicts the possibility of the Peierls transition in FSQWIs fabricated from semiconductor materials with large permittivity.}, journal={Physica B: Condensed Matter}, publisher={Elsevier BV}, author={Komirenko, S.M. and Kim, K.W. and Kochelap, V.A. and Dutta, Mitra and Stroscio, Michael A.}, year={1999}, month={Mar}, pages={522–525} }
 @article{bergman_alexson_nemanich_dutta_stroscio_balkas_davis_1999, title={Phonon dynamics and lifetimes of AlN and GaN crystallites}, volume={4S1}, DOI={10.1557/s1092578300003422}, abstractNote={The quasi-LO and quasi-TO modes of AlN crystallite were investigated. The analysis indicates that the Raman mode behavior concurs with Loudons’ model of mode-mixing in wurtzite (WZ) structure crystals which is due to the long-range electrostatic field. Phononlifetimes of GaN and AlN crystallites were studied via Raman lineshape. It was found that the low energy E2 mode lifetime is about an order of magnitude longer than that of the other modes, and that impurities impact significantly the phonon-lifetimes.}, number={G6.65}, journal={MRS Internet Journal of Nitride Semiconductor Research}, author={Bergman, L. and Alexson, D. and Nemanich, R. J. and Dutta, M. and Stroscio, M. A. and Balkas, C. and Davis, R. F.}, year={1999} }
 @article{bergman_alexson_murphy_nemanich_dutta_stroscio_balkas_shin_davis_1999, title={Raman analysis of phonon lifetimes in AlN and GaN of wurtzite structure}, volume={59}, ISSN={["1550-235X"]}, DOI={10.1103/physrevb.59.12977}, abstractNote={Raman analyses of the lifetimes of phonons in GaN and AlN crystallites of wurtzite structure are presented. In order to ensure the accuracy of the measurement of the phonon lifetimes, an experimental procedure to eliminate the broadening due to the finite slit width was performed. The lifetime analyses indicate that the phonon lifetimes in AlN as well as in GaN fall into two main time regimes: a relatively long time of the ${E}_{2}^{1}$ mode and much shorter times of the ${E}_{2}^{2},$ $E1(\mathrm{TO}),$ and $A1(\mathrm{TO})$ modes. The lifetimes of the ${E}_{2}^{1},$ ${E}_{2}^{2},$ $E1(\mathrm{TO}),$ $A1(\mathrm{TO}),$ and $A1(\mathrm{LO})$ modes of an high-quality AlN crystallite are 4.4, 0.83, 0.91, 0.76, and 0.45 ps, respectively. Moreover, the lifetime of the $A1(\mathrm{LO})$ mode found in this study is consistent with the current phonon-decay model of that mode in wurtzite structure materials. The lifetimes of ${E}_{2}^{1},$ ${E}_{2}^{2},$ $E1(\mathrm{TO}),$ and $A1(\mathrm{TO})$ of a GaN crystallite were found to be 10.1, 1.4, 0.95, and 0.46 ps, respectively. The $A1(\mathrm{LO})$ mode in the GaN was not observed and its absence is attributed to plasmon damping. The lifetime shortening due to impurities was also studied: the lifetimes of the Raman modes of an AlN crystallite, which contains about two orders of magnitude more Si and C impurities relative to the concentration of the high-quality crystallite were found to be 50% shorter.}, number={20}, journal={PHYSICAL REVIEW B}, author={Bergman, L and Alexson, D and Murphy, PL and Nemanich, RJ and Dutta, M and Stroscio, MA and Balkas, C and Shin, H and Davis, RF}, year={1999}, month={May}, pages={12977–12982} }
 @article{belenky_dutta_b. gorfinkel_haddad_iafrate_kim_kisin_luryi_stroscio_sun_et al._1999, title={Tailoring of optical phonon modes in nanoscale semiconductor structures: role of interface-optical phonons in quantum-well lasers}, volume={263-264}, ISSN={0921-4526}, url={http://dx.doi.org/10.1016/S0921-4526(98)01410-0}, DOI={10.1016/S0921-4526(98)01410-0}, abstractNote={This paper discusses the concept of enhancing semiconductor laser performance through tailoring of scattering rates of confined polar-optical phonons. Studies of optically pumped intersubband scattering in coupled quantum-well lasers have demonstrated that interface-phonon-assisted transitions are important in such structures; furthermore, simple analytical expressions have been derived that indicate the importance of interface-phonon scattering in quantum-well lasers. These calculations reveal that the interface-phonon-assisted transitions are dominant for small quantum well dimensions of approximately 40 Å; such dimensions are typical of novel lasers including both the unipolar quantum cascade laser and the tunneling injection laser. Recent numerical calculations have confirmed these effects and have extended them to indicate how confined and interface phonons also affect critical laser properties such as optical gain. The application of confined phonon effects to intersubband lasers is one of the most important applications of confined-phonon physics to the present time.}, journal={Physica B: Condensed Matter}, publisher={Elsevier BV}, author={Belenky, Gregory and Dutta, Mitra and B. Gorfinkel, Vera and Haddad, George I. and Iafrate, G.J. and Kim, K.W. and Kisin, Mikhail and Luryi, Serge and Stroscio, Michael A. and Sun, J.P. and et al.}, year={1999}, month={Mar}, pages={462–465} }
 @misc{iafrate_he_dutta_stroscio_1998, title={Field controlled current modulators based on tunable barrier strengths}, volume={5705824}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={Iafrate, G. J. and He, J. and Dutta, M. and Stroscio, M. A.}, year={1998} }
 @article{yu_kim_bergman_dutta_stroscio_zavada_1998, title={Long-wavelength optical phonons in ternary nitride-based crystals}, volume={58}, ISSN={0163-1829 1095-3795}, url={http://dx.doi.org/10.1103/PhysRevB.58.15283}, DOI={10.1103/physrevb.58.15283}, abstractNote={Phonon modes in column-III--nitride ternary semiconductors are investigated theoretically within the modified random-element isodisplacement model. It is found that ${A}_{1}$ and ${E}_{1}$ branches of optical phonons in wurtzite ${\mathrm{Ga}}_{x}{\mathrm{Al}}_{1\ensuremath{-}x}\mathrm{N}$ and ${\mathrm{In}}_{x}{\mathrm{Ga}}_{1\ensuremath{-}x}\mathrm{N}$ exhibit one-mode behavior. This result is explained by the fact that atomic mass of nitrogen is much smaller than those of other atoms.}, number={23}, journal={Physical Review B}, publisher={American Physical Society (APS)}, author={Yu, SeGi and Kim, K. W. and Bergman, Leah and Dutta, Mitra and Stroscio, Michael A. and Zavada, John M.}, year={1998}, month={Dec}, pages={15283–15287} }
 @article{lee_kim_stroscio_dutta_1998, title={Optical-phonon confinement and scattering in wurtzite heterostructures}, volume={58}, ISSN={0163-1829 1095-3795}, url={http://dx.doi.org/10.1103/PhysRevB.58.4860}, DOI={10.1103/physrevb.58.4860}, abstractNote={We investigate Fr\"ohlich-like electron--optical-phonon interactions in wurtzite structures with single and double heterointerfaces based on the macroscopic dielectric continuum model and the uniaxial model. In addition to confined (for the case of double interfaces), interface, and half-space optical phonon modes as expected from the analogy with zinc-blende structures, propagating modes may exist in wurtzite heterosystems due to anisotropic phonon dispersion. This is especially the case when the dielectric properties of the adjacent heterostructure materials do not differ substantially. The dispersion relations and the interaction Hamiltonians for each of these modes are derived.}, number={8}, journal={Physical Review B}, publisher={American Physical Society (APS)}, author={Lee, B. C. and Kim, K. W. and Stroscio, M. A. and Dutta, M.}, year={1998}, month={Aug}, pages={4860–4865} }
 @article{teng_sun_haddad_stroscio_yu_kim_1998, title={Phonon assisted intersubband transitions in step quantum well structures}, volume={84}, ISSN={0021-8979 1089-7550}, url={http://dx.doi.org/10.1063/1.368277}, DOI={10.1063/1.368277}, abstractNote={We evaluate effects of heterointerfaces on optical phonon modes and phonon assisted electron intersubband transition rates in step quantum well structures for intersubband lasers. Various phonon modes and electron–phonon interaction Hamiltonians, including the interface modes, confined longitudinal-optical modes, and half space modes in the quantum well structures are calculated based on the macroscopic dielectric continuum model and microscopic analysis. The transfer matrix method is used to calculate the interface modes. The intersubband transition rates due to electron–phonon scattering by these phonon modes are evaluated using Fermi’s golden rule, with the electron wave functions obtained by solving the Schrödinger equation for the heterostructures under investigation. Our results show that, compared with the transition rates in the same structures calculated using the bulk phonon modes and the bulk Fröhlich interaction Hamiltonian, the electron interface–phonon interactions give significantly larger transition rates up to an order of magnitude. Therefore, the effects of localized phonon modes, especially the interface modes, must be taken into consideration for optimal device design.}, number={4}, journal={Journal of Applied Physics}, publisher={AIP Publishing}, author={Teng, H. B. and Sun, J. P. and Haddad, G. I. and Stroscio, Michael A. and Yu, SeGi and Kim, K. W.}, year={1998}, month={Aug}, pages={2155–2164} }
 @book{dutta_stroscio_1998, title={Quantum-based electronic devices and systems}, ISBN={9810237006}, publisher={Singapore; River Edge, NJ: World Scientific}, author={Dutta, M. and Stroscio, M. A.}, year={1998} }
 @article{komirenko_kim_stroscio_kochelap_1998, title={Renormalization of acoustic phonon spectra and rudiments of the Peierls transition in free-standing quantum wires}, volume={58}, ISSN={0163-1829 1095-3795}, url={http://dx.doi.org/10.1103/PhysRevB.58.16360}, DOI={10.1103/physrevb.58.16360}, abstractNote={We have analyzed a quasi-one-dimensional electron-phonon system coupled through the deformation potential interaction. In a free-standing quantum wire, we calculated the renormalization of acoustic phonon spectra. The results illustrate remarkable cusplike features in the vicinity of the phonon wave vector that is twice the electron Fermi wave vector. These cusps are rudiments of the Peierls transition in the quasi-one-dimensional system. The transition is suppressed in conventional materials because of the electrostatic effects. For such materials, however, the renormalization of acoustic phonon spectra and the cusps can be observed in various acoustical and optical experiments. Furthermore, our study demonstrates that the Peierls transition can occur in free-standing quantum wires fabricated from semiconductor materials with high permittivity.}, number={24}, journal={Physical Review B}, publisher={American Physical Society (APS)}, author={Komirenko, S. M. and Kim, K. W. and Stroscio, M. A. and Kochelap, V. A.}, year={1998}, month={Dec}, pages={16360–16368} }
 @article{sirenko_kim_stroscio_1997, title={Near-surface electrons and acoustic phonons: Energy and momentum relaxation}, volume={56}, ISSN={0163-1829 1095-3795}, url={http://dx.doi.org/10.1103/PhysRevB.56.15770}, DOI={10.1103/physrevb.56.15770}, abstractNote={We study energy and momentum relaxation of a two-dimensional (2D) electron channel located at a finite distance $\mathcal{l}$ from a free crystal surface. The interaction with a complete set of bulklike, totally reflected, and Rayleigh acoustic phonon modes is taken into account. In most cases of interest the relaxation rates have the same temperature dependence as for 2D or bulk electrons interacting with bulk phonons. Numerical calculations demonstrate that the presence of a surface results in approximately a 10% modification of scattering rates in the high-temperature region. In the opposite limit (Bloch-Gr\"uneisen regime), the contribution of the surface phonons may dominate over that of bulklike modes. Oscillations of the relaxation rates as a function of the distance $\mathcal{l}$ between the electron channel and the surface are also predicted.}, number={24}, journal={Physical Review B}, publisher={American Physical Society (APS)}, author={Sirenko, Yuri M. and Kim, K. W. and Stroscio, Michael A.}, year={1997}, month={Dec}, pages={15770–15781} }
 @article{yu_kim_stroscio_iafrate_sun_haddad_1997, title={Transfer matrix method for interface optical-phonon modes in multiple-interface heterostructure systems}, volume={82}, ISSN={0021-8979 1089-7550}, url={http://dx.doi.org/10.1063/1.365649}, DOI={10.1063/1.365649}, abstractNote={Interactions of carriers with interface optical phonons dominate over other carrier–phonon scatterings in narrow quantum-well structures. Herein, a transfer matrix method is used to establish a formalism for determining the dispersion relations, electrostatic potentials, and Fröhlich interaction Hamiltonians of the interface optical phonons for multiple-interface heterostructure systems within the framework of the macroscopic dielectric continuum model. This method facilitates systematic calculations for complex structures where the conventional method is very difficult to implement. Several specific cases are treated to illustrate the advantages of the general formalism.}, number={7}, journal={Journal of Applied Physics}, publisher={AIP Publishing}, author={Yu, SeGi and Kim, K. W. and Stroscio, Michael A. and Iafrate, G. J. and Sun, J.-P. and Haddad, G. I.}, year={1997}, month={Oct}, pages={3363–3367} }