Characterization of p-Al_xGa_(1-x)As/p-GaAs structure studied by surface photovoltage in metal-insulator-semiconductor configuration

摘要

Metal-insulator-semiconductor (MIS) configuration has been used to measure the surface photovoltage (SPV) spectroscopy of p-GaAs substrate and p-Al_xGa_(1-x)As/p-GaAs structure. The p-AlGaAs layer was on p-type GaAs substrate grown by metal organic chemical vapor deposition. An ideality factor was used to investigate the relationship of the measured SPV signals to the "real" SPV signals. Dependence of the surface photovoltage on incident photon intensity for band-to-band excitation was adopted for the calculation of ideality factor. The ideality factor of MIS configuration was found to be 0.008 for our sample with both sides polished in air ambient. In order to calculate the parameters of p-Al_xGa_(1-x)As/p- GaAs structure, the minority carrier diffusion length in the GaAs substrate was determined from a linear plot of inverse SPV vs. inverse absorption coefficient by intercepting the line with the x-axis. Other parameters of p-Al_xGa_(1-x)As/p-GaAs were studied through the simulation of surface photovoltage.