Efficiency calculations of thin-film GaAs solar cells on Si substrates

Abstract

Dislocation effect upon the efficiency of single-crystal thin-film AlGaAs-GaAs heteroface solar cells on Si substrates is analyzed. Solar-cell properties are calculated based on a simple model; in the model, dislocations act as recombination centers to reduce the minority-carrier diffusion length in each layer and increase the space-charge layer recombination current. Numerical analysis is also carried out to optimize thin-film AlGaAs-GaAs heteroface solar-cell structures. The fabrication of thin-film AlGaAs-GaAs heteroface solar cells with a practical efficiency larger than 18% on Si substrates appears possible if the dislocation density in the thin-film GaAs layer is less than 106 cm−2.

Analysis of the impact of dislocation distribution on the breakdown voltage of GaAs-based power varactor diodes

“…This is in accord with the observations, wherein a correlation was found to exist between reverse leakage current density ͑J 0 ͒ and relative dislocation densities ͑N DIS ͒. Such a correlation is supportive of the above hypothesis, because J 0 is a function of minority-carrier lifetime, , in the space-charge region 2,16 and is dependent on N DIS as follows:…”

“…Recent studies have shown that these effects manifest themselves in differing guises for a wide variety of devices, e.g., dislocations can reduce the current gain in AlGaAs/GaAs heterojunction bipolor transistors ͑HBTs͒, 1 and heteroepitaxial solar cells have low efficiencies due to misfit and thermally induced dislocations acting as recombination centers. [2][3][4] This article reports on the use of synchrotron x-ray topography ͑SXRT͒ to analyze the defect/dislocation distributions within wafer substrates and their correlation with substandard performance of GaAs power varactor diodes.…”

40% efficient metamorphic GaInP∕GaInAs∕Ge multijunction solar cells

“…Other devices can also benefit from these materials, such as heterojunction bipolar transistors, 1.3 and 1.55 m photodetectors and lasers, and InP-onGaAs and GaAs-on-Si devices in general. Many research studies have investigated the promise of metamorphic materials for solar cells, [3][4][5][6][7][8][9][10][11] often citing 40% conversion efficiency as a possible goal. This letter reports on three-junction metamorphic and lattice-matched cells that have now surpassed the 40% efficiency milestone.…”

III-V Device Integration on Silicon Via Metamorphic SiGe Substrates

“…Consistent with the wide range of TDD's that have been reported for varying GaAs/Si integration approaches, a large variation in lifetime has been measured stemming from the epitaxial hurdles present in the GaAs/Si material system; namely, a 4% lattice mismatch and a nonpolar/polar interface. The influence of lattice mismatch on lifetime has been modeled as τ max represents the minority carrier lifetime in the absence of TDs and τ TDD represents the lifetime contribution resulting from recombination at TDs, which depends on D, on the minority carrier diffusion coefficient, and on the TDD (10,12). In one instance, minority carrier lifetime measurements facilitated using GaAs double heterostructures (DHs) grown on Si substrates via direct epitaxy using III-V strained-layer superlattices as interlayers have been reported to be up to 2 ns in n-type GaAs.…”