Phase-sensitive analysis of a two-color infrared photodetector using photoreflectance spectroscopy

The phase diagrams of photoreflectance spectra were investigated for an InGaAs two-color infrared photodetector. The diagrams for a high excitation intensity revealed that the spectrum is multi-component. The origin of these components was investigated, and the photoreflectance spectra and phase diagrams were also measured for an angle-polished version at different depths. With the help of the polished sample, the variation of the phase delay angles and the trapping time constants was tracked for different depths. Additionally, the polished version enables us to find a confirmation for the origins of the multi-component nature of the whole phase diagram. It can be concluded that when the phase delays or time constants of various components are very close, more attention should be paid to interfering with the phase-sensitive investigations of layered materials. As a main result, the consistency of the phase delay with interface trap densities was confirmed qualitatively. Using a reciprocal space map of the sample, this result can be a piece of experimental evidence for a correlation between the photoreflectance time constant and trap densities in the junctions. This non-contact method enables the characterization of layered devices, offering a valuable tool for achieving high-performance devices.