Temperature dependence of the photovoltage from Franz-Keldysh oscillations in a GaAs p(+)-i-n(+) structure

Abstract

The temperature dependences of the junction electric fields and photovoltage have been investigated for a GaAs p(+)-i-n(+) structure by using photoreflectance (PR) spectroscopy. The electric field strength was examined through three types of Franz-Keldysh oscillation (FKO) analyses; then, the photovoltage was evaluated with respect to temperature in the range from 30 to 300 K. From the PR results, we observed two electric fields that are estimated to originate from two regions of FKOs in undoped GaAs and from the space charge region in highly-doped GaAs. The electric field under illumination decreased with decreasing temperature while the photovoltage obtained from the electric field increased. We also demonstrate that PR spectroscopy is a good method for investigating the photovoltaic effect in solar-cell structures.