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Al{sub x}Ga{sub 1{minus}x}Sb window layers for InGaAsSb/GaSb thermophotovoltaic cells
Journal article

Al{sub x}Ga{sub 1{minus}x}Sb window layers for InGaAsSb/GaSb thermophotovoltaic cells

Joseph T. South, Michael G. Mauk, John D. Meakin, Jeffrey A. Cox and Paul E. Sims
AIP Conference Proceedings, v 460(1)
01 Mar 1999
DOI: https://doi.org/10.1063/1.57839

Abstract

ALUMINIUM COMPOUNDS ANTIMONY COMPOUNDS DIRECT ENERGY CONVERSION EMISSIVITY FABRICATION GALLIUM ARSENIDES INDIUM ANTIMONIDES LATTICE PARAMETERS PASSIVATION QUATERNARY ALLOY SYSTEMS SOLAR ENERGY SPECTRAL RESPONSE TERNARY ALLOY SYSTEMS THERMOPHOTOVOLTAIC CONVERTERS
We report results of a comparative study of AlSb-based window layers for InGaAsSb/GaSb TPV cells made by liquid-phase epitaxy (LPE). Previous work has shown that an AlGaAsSb window layer significantly improves the performance of InGaAsSb/GaSb TPV cells. As expected, the window layer enhances short-wavelength spectral response and increases the open-circuit voltage by reducing the reverse-saturation current of the diode. We present results for a simpler alternative window layer based on the ternary AlGaSb alloy. We fabricated, characterized, and compared InGaAsAsSb TPV of three types: 1. with an AlGaAsSb window layer, 2. with an AlAsSb window layer, and 3. with no window layer. Both {ital p}-on-{ital n} ({ital p}-type InGaAsSb emitter; {ital n}-type InGaAsSb base) and {ital n}-on-{ital p} ({ital n}-type InGaAsSb emitter; {ital p}-type InGaAsSb base) homojunction cell configurations were investigated. The InGaAsSb layers have a {approximately}0.55-ev bandgap and are lattice-matched to a GaSb substrate. As anticipated, both AlGaSb and AlGaAsSb passivated TPV cells were superior to cells without a window layer. The AlGaAsSb/InGaAsSb window/emitter interface is closely lattice matched and would be expected to provide better surface passivation than AlGaSb/InGaAsSb window/emitter interface which has a 0.6{percent} lattice mismatch. On the contrary, our experimental results showed that, based on a comparison of spectral response, AlGaSb window layers were somewhat more effective than AlGaAsSb in passivating the front surface of InGaAsSb diodes. These results demonstrate the viability of a simpler ternary AlGaSb alloy as an alternative to the quaternary AlGaAsSb alloy as a window layer material. {copyright} {ital 1999 American Institute of Physics.}

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