@inproceedings{bedair_harmon_carlin_sayed_colter_2016, title={Annealed high band gap tunnel junctions with peak current densities above 800 A/cm(2)}, DOI={10.1109/pvsc.2016.7750052}, abstractNote={The development of high-performance high band gap tunnel junctions is critical for producing efficient multijunction photovoltaic cells that can operate at high solar concentrations. The n-InGaP/GaAs/p-AlGaAs TJ has been demonstrated to produce peak tunneling currents (Jpk) above 1000 A/cm2 with minimal absorption losses due to the use of thin (<50 Â) GaAs layer. We will report on the growth and device modeling of these structures as well as the effect of high temperature annealing on Jpk. A method to grow TJ structures resistant to annealing will be described, which has resulted in thermally annealed TJ with Jpk above 800 A/cm2. This is the highest value ever reported for an annealed high band gap TJ. Device modeling has been used to investigate the source of the high tunneling current, as well as the behavior of the annealed TJ.}, booktitle={2016 ieee 43rd photovoltaic specialists conference (pvsc)}, author={Bedair, S. M. and Harmon, J. L. and Carlin, C. Z. and Sayed, I. E. H. and Colter, P. C.}, year={2016}, pages={2320–2322} }
 @article{bedair_carlin_harmon_sayed_colter_2016, title={High Performance Tunnel Junction with Resistance to Thermal Annealing}, volume={1766}, ISSN={["0094-243X"]}, DOI={10.1063/1.4962071}, abstractNote={The availability of high band gap (>1.9 eV) tunnel junctions (TJ) with large peak current densities (Jpk) is crucial for the development of multijunction photovoltaic cells that can operate at concentrations above 1000 suns. Existing TJ designs include thick GaAs layers which reduce the overall efficiency due to absorption. We have developed an n-InGaP/GaAs/p-AlGaAs structure with a GaAs layer that is 50 A or thinner that has an as-grown Jpk above 2000 A/cm2 an annealed Jpk above 1000 A/cm2. Due to the memory effect of the Te n-type dopant, modifications to the shut off time of the DETe precursor produced the high Jpk that was observed.}, journal={12TH INTERNATIONAL CONFERENCE ON CONCENTRATOR PHOTOVOLTAIC SYSTEMS (CPV-12)}, author={Bedair, S. M. and Carlin, C. Zachary and Harmon, Jeffrey L. and Sayed, Islam E. Hashem and Colter, P. C.}, year={2016} }
 @article{bedair_harmon_carlin_sayed_colter_2016, title={High performance as-grown and annealed high band gap tunnel junctions: Te behavior at the interface}, volume={108}, ISSN={["1077-3118"]}, DOI={10.1063/1.4951690}, abstractNote={The performance of n+-InGaP(Te)/p+-AlGaAs(C) high band gap tunnel junctions (TJ) is critical for achieving high efficiency in multijunction photovoltaics. Several limitations for as grown and annealed TJ can be attributed to the Te doping of InGaP and its behavior at the junction interface. Te atoms in InGaP tend to get attached at step edges, resulting in a Te memory effect. In this work, we use the peak tunneling current (Jpk) in this TJ as a diagnostic tool to study the behavior of the Te dopant at the TJ interface. Additionally, we used our understanding of Te behavior at the interface, guided by device modeling, to modify the Te source shut-off procedure and the growth rate. These modifications lead to a record performance for both the as-grown (2000 A/cm2) and annealed (1000 A/cm2) high band gap tunnel junction.}, number={20}, journal={APPLIED PHYSICS LETTERS}, author={Bedair, S. M. and Harmon, Jeffrey L. and Carlin, C. Zachary and Sayed, Islam E. Hashem and Colter, P. C.}, year={2016}, month={May} }
 @article{samberg_carlin_bradshaw_colter_harmon_allen_hauser_bedair_2013, title={Effect of GaAs interfacial layer on the performance of high bandgap tunnel junctions for multijunction solar cells}, volume={103}, ISSN={["1077-3118"]}, DOI={10.1063/1.4819917}, abstractNote={The effect of the heterojunction interface on the performance of high bandgap InxGa1−xP:Te/Al0.6Ga0.4As:C tunnel junctions (TJs) was investigated. The insertion of 30 A of GaAs:Te at the junction interface resulted in a peak current of 1000 A/cm2 and a voltage drop of ∼3 mV for 30 A/cm2 (2000× concentration). The presence of this GaAs interfacial layer also improved the uniformity across the wafer. Modeling results are consistent with experimental data and were used to explain the observed enhancement in TJ performance. This architecture could be used within multijunction solar cells to extend the range of usable solar concentration with minimal voltage drop.}, number={10}, journal={APPLIED PHYSICS LETTERS}, author={Samberg, Joshua P. and Carlin, C. Zachary and Bradshaw, Geoff K. and Colter, Peter C. and Harmon, Jeffrey L. and Allen, J. B. and Hauser, John R. and Bedair, S. M.}, year={2013}, month={Sep} }
 @inproceedings{hauser_carlin_harmon_bradshaw_samberg_colter_bedair_2013, title={Modeling an InGaP/AlGaAs tunnel junction containing an AlAs diffusion barrier}, DOI={10.1109/pvsc.2013.6744883}, abstractNote={Cost improvements in concentrated photovoltaic (CPV) systems can be achieved by operating at increased solar concentration. Current multijunction CPV systems are limited to about 1000× concentration by the performance of the tunnel junctions (TJ) which connect the subcells. The TJ requires materials which are doped in excess of 1019 cm-3 in order to operate effectively, and so are susceptible to diffusion during the growth of subsequent layers. This paper considers a tunnel junction comprised of tellurium doped n+-InGaP and carbon doped p+-AlGaAs with a several monolayers of AlAs at the interface. The diffusion profile of the dopants was found and used to calculate the tunneling current through a junction. Due to uncertainty in the diffusion constants of C and Te in the three layers, the tunneling current was calculated for several values of Dt. The diffusion constant ratio in the AlAs was taken as a fraction of the diffusion constant in the other two layers. A significant increase in peak tunneling current was seen for Dt>1×10-14 cm2 when a three monolayer thick AlAs barrier was present.}, booktitle={2013 ieee 39th photovoltaic specialists conference (pvsc)}, author={Hauser, J. and Carlin, Z. and Harmon, J. and Bradshaw, G. and Samberg, J. and Colter, P. and Bedair, S.}, year={2013}, pages={2082–2085} }