Investigation of capacitance for InAs/GaAs quantum dot solar cells by photoreflectance

The study provides experimental validation for the correlation between the photoreflectance signal's time constant and the capacitances of various p- n junction quantum-dot solar cells. Photoreflectance spectra were measured on four structures with varying InAs/GaAs quantum dot layer thicknesses (1.7-3 monolayers), and time constants were extracted from the phase diagrams. A linear relationship was observed between these time constants and the cells' capacitances. Analysis of the phase diagrams for different chopping frequencies revealed that this approach allows for the assessment of capacitances of a sample set through a single photoreflectance measurement. These findings underscore the potential of photoreflectance as a straightforward, contactless technique for comparing junction capacitance across samples. Furthermore, this work could enhance our understanding of photoreflectance in solar cell characterization and present a practical tool for evaluating capacitance in various optoelectronic devices, broadening the utility of nondestructive characterization techniques.