AlGaAs/GaAs/InGaAs composite MQW structures for photovoltaic applications

Abstract

AlGaAs/GaAs/InGaAs composite MQW structures were theoretically studied and simulated. The computer simulation indicated that an appropriate composite MQW, both with symmetrical and non-symmetrical structures, could keep | ψ| 2 of quantized carriers at proper locations in electric-field-tilted quantum wells, so the efficient transition by photon absorption would be possible and applicable for photovoltaic cells which have the composite MQW as the active region. The AlGaAs/GaAs MQW and GaAs/InGaAs (4 x) SQW structures were separately prepared by MBE and were evaluated for their spectral responses. The AlGaAs/GaAs MQW has a high response at a short wavelengths (peak at 685 nm) due to the quantized states in GaAs wells, while the GaAs/InGaAs SQW has a broader spectral response covering longer wavelengths (600–850 nm) because of the strong absorption in the GaAs barrier and substrate. However, (4 x) photoluminescence peaks at 900–1100 nm that werefound from GaAs/InGaAs strained quantum wells at room temperature are promising evidence for the longer wavelength spectral response. The AlGaAs/GaAs/InGaAs composite SQW and MQW samples were experimentally prepared by MBE techniques and tested for their optical properties. The broader photoluminescence peak was observed and reflected the nature of the composite structure. The study on the photospectral response of composite MQW structures has been conducted which provides the basic information for high performance solar cell design.