We report the fabrication and characterization of lattice matched single junction InGaAs thermophotovoltaic cells grown on InP substrates with an EQE >90% over a broad spectral range. The I-V characteristics of the cells are examined for a range of operating temperatures and illumination conditions. An accurate model of the cell performance, including the flat-spot behaviour exhibited by the cells, is developed using the commercial PC1D package. We use this model to estimate the output of these cells with an example low-cost spectral control system, which suggest that these cells would produce system efficiencies >10%, with the potential for efficiencies >20%.

Phonon energies in inAs,,Sb, ternary alloys, grown on GaAs by molecular beam epitaxy, have been studied by Raman scattering. The microstructure for this alloy system depends strongly on the growth temperature For growth temperatures above 400"C, transmission electron microscopy (TEM) shows the alloy epilayer to be homogeneous. Raman spectra of these homogeneous InAsSb alloys show a strong InAs-like longitudinal optical (LO) phonon line, as well as an InSb-like LO line. throughout the composition range. The frequency of the InAs-like LO phonon varies linearly with composition. For growth temperatures below 400°C and compositions near t h e middle of the range, an interleaved platelet structure, arising from phase separation, is observed in TEM. Effects of phase separation in these alloys have been observed in the Raman spectra.

We report on characterization studies of high quality metal-organic vapor phase epitaxy and molecular beam epitaxy grown GaAs/InGaAs quantum wells, set within p-i-n diodes, to determine the well widths, indium mole fractions, and conduction band offset. We present photocurrent spectra containing a larger number of transitions than revealed in photoluminescence or photoluminescence excitation experiments. The energies of these transitions have been modeled using a theoretical characterization tool known as ‘‘contouring,’’ which is used in this strained system for the first time. This has enabled determination of the conduction band offset in GaAs/InGaAs quantum wells, to a value between 0.62 and 0.64, for a range of indium fractions between 0.155 and 0.23. As a final, additional check on our results, we compare the field dependence of the e1-hh1 exciton transition energy with our theoretical calculations and find good agreement.

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