Correlation between the time constant of a photoreflectance signal and the quantum efficiency of a p-n junction

A formulation was derived to connect the time constant of the photoreflectance signal and the quantum efficiency of a p-n junction. The characteristic time constants were achieved by the phase diagram of the photoreflectance spectra. An explicit formulation of the characteristic time constant of the junction is then derived. In this semi-empirical formula, the characteristic time constant is related to the photovoltage, the excitation wavelength, the intensity, the permittivity, the depletion width, and, most importantly, the quantum efficiency. Two structures comprising p-n and p-i-n GaAs junctions were examined, and the quantum efficiency of the junctions was estimated by the method for different excitation wavelengths. The proposed formulation can predict the wavelength dependency of the quantum efficiency for GaAs-based junctions and that the quantum efficiency of a p-i-n structure is higher than the p-n structure, as expected from the literature. This work can be regarded as an investigation to connect the photoreflectance spectroscopy to the quantum efficiency in the junctions. Moreover, it can be used as a simple tool to find a more physical meaning for the time constant.