Measurement of Carrier Recombination Parameters in III-V Compounds for Photovoltaic Cell Design Optimization
PIs: Dmitri Donetski, Gregory Belenky
The leading role of III-V compound industry in microwave and photonic applications is established by high electron mobility and effective light emission in these materials. The 1st and 2nd generations of III-V compound electronics are based on epitaxial materials with lattice constants near 5.65 and 5.87 A grown on GaAs and InP substrates, respectively. The fabrication and testing technologies for these materials have been developed to the level when device parameters are nearly limited by material properties. While the 3rd generation devices including ~6.1 A GaSb- and InAs-based ones overcome these limits, maturity of the technology for these materials is not yet sufficient to realize its potential.
n frames of the thermophotovoltaic (TPV) energy generation program we developed the non-destructive methods for evaluation of the material quality of 0.5-0.6 eV InGaAs and InGaAsSb epitaxial structures and TPV cells designed for radiators with temperatures about 1000 C. The methods are primary based on minority carrier lifetime measurements performed by time-resolved photoluminescence and optical modulation response in wide ranges of experimental conditions: with the excess carrier concentrations as low as 1014 cm-3 for testing undoped and unintentionally doped materials, the time resolution of 0.2 ps for testing heavily doped materials and the spatial resolution of 20 flm for evaluation of the as grown material homogeneity and effects of processing on device parameter degradation. Using the developed approach the carrier recombination terms were evaluated and the modeling parameters were determined for effective optimization of the TPV cell design. There is a prospective to use TPV energy conversion technology for industrial waist heat utilization and for generation of auxiliary electrical power with radiation of combustion sources. These systems can function in extreme environment conditions where competitive technologies fail to operate.