KEYWORDS: Solar cells, Aluminum, Energy conversion efficiency, Gallium, Antimony, Multijunction solar cells, Solar radiation, Superlattices, Silicon, Molecular beam epitaxy
We report the design and fabrication of Al0.95Ga0.05As0.56Sb0.44/Al0.75Ga0.25As0.56Sb0.44 solar cell as a top cell for triple-junction cell grown on InP substrate. The digital alloy technique, capable to grow high quality materials with composition falling in miscibility gap, was employed to grow high quality Al(Ga)AsSb to realize Al(Ga)AsSb solar cells. A test Al0.95Ga0.05As0.56Sb0.44/Al0.75Ga0.25As0.56Sb0.44 cell grown by molecular beam epitaxy was fabricated and characterized. The measured energy conversion efficiency is up to 8.9% under simulated AM0 radiation for the Al0.95Ga0.05As0.56Sb0.44/Al0.75Ga0.25As0.56Sb0.44 cell without AR coating on cell surface.
IR photo detectors are in high demand for various military and civilian applications, such as airborne surveillance, remote sensing, environmental monitoring, and spectrometry. Recently InAs/GaSb type II superlattice (T2SL) has attracted numerous R and D interest since SLS is the only IR material that has a theoretical prediction of higher performance than HgCdTe. Here we report the improvement of SL photo diodes through a new design with highly-strained type-II superlattice (HS-T2SL). The HS-T2SL consists of a highly compressively strained thick InSb layer at InAs/GaSb interfaces. The presence of coherent strain shifts the band edges such that the SL energy gap is reduced. This reduced band gap is advantageous to photodetectors because longer cut-off wavelengths can be obtained with reduced layer thickness in the strained SL. The highly compressive strain in HS-T2SL also leads to an even higher optical absorption coefficient and lower dark current. Applying this new design resistance-area product (R0A) is measured as high as 2.1 Ohm-cm2 at 85K for 14.8-μm-cutoff photo diodes without any dark current suppression barriers. The fabricated 14.5μm-cutoff photo diode shows Johnson-noiselimited peak detectivity of 8.4×1010 cmHz1/2/W at zero bias at 85K.
In this paper we report improved device performance for type II superlattice (SL) photo
diodes by inserting a graded AlGaSb barrier layer inserted into the depletion region of the
PIN diode to suppress dark current and employing SiO2 as a passivation layer. The I-V
characteristics shows presence of AlGaSb barrier layer in the device structure increased
R0A values by up to a factor of 40 times. Sidewall resistivity was increased by an order
of magnitude with SiO2 passivation. The fabricated photo diode with λc=12.8-μm shows
peak responsivity of 3.7 A/W at 10.6 μm and Johnson noise limited peak detectivity of
1×1011 cmHz1/2/W under zero bias at 83 K under 300 K background radiation with a 2π
field-of-view.
Conference Committee Involvement (2)
Nanophotonics and Macrophotonics for Space Environments IX
14 August 2015 | San Diego, California, United States
Nanophotonics and Macrophotonics for Space Environments VIII
18 August 2014 | San Diego, California, United States
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