Research

W. Yang, et al., J. Appl. Phys. 115, 203105 (2014).
This paper reports the proposal, design, and demonstration of ultra-thin GaAs single-junction solar cells integrated with a reflective back scattering layer to optimize light management and minimize non-radiative recombination. The structure of the demonstrated solar cells consists of an In0.49Ga0.51P/GaAs/In0.49Ga0.51P double-heterostructure PN junction with an ultra-thin 300 nm thick GaAs absorber, combined with a 5 µm thick Al0…

J.-J. Li, L. et al., Applied Physics Letters 101, 061915-061915. (2012)
CdSe/CdTe type-II superlattices grown on GaSb substrates by molecular beam epitaxy are studied using time-resolved and steady-state photoluminescence (PL) spectroscopy at 10 K. A carrier lifetime of 188 ns is observed in time-resolved PL measurements. The steady-state PL peak position exhibits a blue shift with increasing excess carrier concentration. This effect can be explained by band bending as a result of…

S. H. Lim, et al., Progress in Photovoltaics: Research and Applications, (2011).
The effects of luminescence coupling on the external quantum efficiency (EQE) measurement of an InGaP/InGaAs/Ge triple junction solar cell were investigated. A small signal model was used to study the interaction of the subcells during EQE measurement. It was found that an optical–electrical feedback mechanism results in EQE measurement artifacts. Measurements of luminescence from the InGaP p–n junction…

D. Ding, et al., J. Appl. Phys. 110, 123104 (2011).
A semi-analytical model is constructed for single- and multi-junction solar cells. Four typical planar structures with the combinations of a smooth/textured top surface and an absorbing/reflecting substrate (or backside surface) are investigated. The below-bandgap tail absorption increases the short-circuit current but decreases the output and open-circuit voltage. Two important design rules for both single- and multi-junction…

Type-II Superlattice Semiconductors for Infrared Photodetectors

E. H. Steenbergen, et al., Appl. Phys. Lett. 99, 251110 (2011).
Time-resolved photoluminescence measurements reveal a minority carrier lifetime of >412 ns at 77 K under low excitation for a long-wavelength infrared InAs/InAs0.72Sb0.28 type-II superlattice (T2SL). The considerably longer lifetime is attributed to a reduction of non-radiative recombination centers with the removal of Ga from the…

MBE growth of various kinds of III-V and II-VI compound semiconductors.  
A unique twin-chamber MBE system allows growth of any composition of III-V and II-VI alloys. Monolithic intergration material platform for various optoelectronic and electronic device applications.

Photon extraction factor vs spontaneous emission efficiency for the maximum photon recycling case in a and for the minimum photon recycling case in b. The cooling efficiency is positive in the shaded area and zero along the solid line. The ideal cooling coefficient ic=kT/Eg used is for the GaAs band gap energy. 04

J.-B. Wang, et al., J. Appl. Phys. 100, (4), 043502 (2006).
Luminescence refrigeration in semiconductors is studied using a model that includes the rate…

E. H. Steenbergen, et al. Appl. Phys. Lett. 97 161111-161114 (2010).
A two-terminal multicolor photodetector that is most advantageous for greater than two bands is proposed. Individual color detection is realized with appropriate optical biasing. This concept is demonstrated experimentally using a three-color photodetector and biasing light emitting diodes. The measured linear dynamic range is greater than four orders of magnitude.

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