Effect of biasing under illumination on GaAsBi/GaAs multiple quantum wells for solar cell performance

Gallium arsenide bismide (GaAsBi) is a potential candidate to replace InGaAs as the middle-junction structure in a multiple junction solar cell due to its lower level of lattice strain in the structure. The level of strain in the lattice structure is challenging as it can manipulate the total current collected in a solar cell, affecting the total output power. In this study, a GaAsBi multiple quantum wells with GaAs barriers (GaAsBi/GaAs) p-i-n structure was grown by using MBE machine and fabricated. A current-voltage (I-V) under illumination measurements were conducted to study the effect of biasing with the presence of light. This result is compared with a strained-balance InGaAs/GaAsP device. From the photocurrent output, it is shown that GaAsBi can achieve a longer cut-off wavelength, around 1053nm compared to InGaAs/GaAsP, with only 930 nm cut-off wavelength. The result also shows that the device is extracting low carriers from the photon sweeps at zero bias. A small amount of reverse bias is needed to allow carrier enhancement and increase the number of carriers collected by the device. As the forward bias is applied, photocurrent value drops as the forward dark current dominates the total current output. In conclusion, GaAsBi/GaAs MQW can be a competitive alternative to InGaAs in achieving a 1eV material system for photovoltaic, especially when the growth and structural component is optimized, improving its strain level and dark current density.