Characterization of III-V compounds-based optoelectronic devices using cross-sectional scanning probe microscopy
III-V compound-based solar cells (SCs) that contain elaborate nanostructures have been rigorously investigated as a way to harvest a wide range of the solar spectrum. However, the energy conversion efficiency of those SCs remains low and further improvement of device performance is needed to catch up with silicon-based ones. A much deeper understanding of the role of the nanostructures in the photovoltaic conversion process is, therefore, required to gain effective design criteria. The first step toward this is to investigate the correlation between local electronic properties at the relevant SC junctions (including formation of built-in potential and its change under light irradiation) and macroscopic device characteristics (which can be determined from conventional current-voltage measurements).
In this talk, we report (i) characterization of the electrical potential along the p-i-n junction of a multiple quantum well SC using Kelvin probe force microscopy, and (ii) direct visualization of nitrogen (N) impurity states in dilute GaNAs using scanning tunneling microscopy.