Direct-Gap 2.1-2.2 eV AlInP Solar Cells on GaInAs/GaAs Metamorphic Buffers

TitleDirect-Gap 2.1-2.2 eV AlInP Solar Cells on GaInAs/GaAs Metamorphic Buffers
Publication TypeJournal Article
Year of Publication2016
AuthorsVaisman, M, Mukherjee, K, Masuda, T, Yaung, KNay, Fitzgerald, EA, Lee, MLarry
JournalIeee Journal of Photovoltaics
Pagination571 - 577
Date Published2016/03//
ISBN Number2156-3381
Keywordsalgainp, AlInP, diodes, electron, III-V semiconductor materials, layer, molecular-beam epitaxy, photovoltaic cell, substrate misorientation, vapor-phase epitaxy, wide bandgap

AlInP offers the highest direct bandgap (E-g) among nonnitride III-V materials, making it attractive for top cell applications in five-to-six-junction solar cells. We present novel 2.05-2.15 eV direct-gap AlInP solar cells, grown on GaInAs/GaAs-graded buffers by metal-organic chemical vapor deposition (MOCVD). Despite the high Al content of 36-39% in the active regions, secondary ion mass spectrometry results indicate oxygen concentrations less than 3.5 x 10(16) cm(-3). The AlInP devices we present here exhibit superior photovoltaic performance to GaP and similar performance tometamorphic GaInP solar cells, reaching a E-g-voltage offset of 0.57 V. Design enhancements based on device and material characterization led to improvements of over similar to 4x in short-circuit current density from our first-generation AlInP devices. Our results indicate that a p-i-n device design is necessary to account for low minority carrier diffusion lengths in AlInP solar cells; additionally, diffusion of Zn dopant atoms poses another challenge that must be accounted for in cell design. The effect of offcut on cell performance was also investigated, with improved solar cells on samples offcut toward the A plane. The promising results in this work provide an alternative path toward realizing high-E-g top cells with possible applications in upright metamorphic multijunction solar cells.

Short TitleIEEE J. Photovolt.