Photovoltaic conversion in the multiple quantum well indium gallium arsenic phosphide semiconductor heterostructures (Indium gallium arsenic phosphide)

The topic of this thesis is the physics of carrier transport and photovoltaic conversion in InP-based multiple quantum well (MQW) and bulk heterostructures. A new concept of enhancing MQW solar cell conversion efficiency using sequential resonant tunneling (SRT) transfer was introduced. MQW InGaAsP/InP solar cells were designed, grown and investigated. Sample characterization was conducted using a wide set of techniques: photoluminescence (PL) and photocurrent (PC) measurements, current-voltage (IN) measurements, electroreflectance and secondary ion mass spectrometry. PL, I-V and PC data were studied for their temperature and bias dependence. Enhancement of the photocurrent and reduction of the radiative recombination losses in an InGaAsP/InP MQW heterostructure due to built-in SRT have been observed for the first time. Photovoltaic efficiency measurements showed that the MQW solar cells outperformed the control non-MQW cells by 13% (relative efficiency of the control sample taken as a 100%). The effect of the SRT on the performance was relatively small because of (1) the small magnitude of the SRT peak and (2) the location of the peak out of the cell operational range. Based on the obtained results the criteria for successful implementation of the SRT in MQW structures for the purpose of enhancement of photovoltaic efficiency have been established.