Microscopic surface photovoltage spectroscopy of the CdSe/ZnCdMgSe quantum dots structures

We present room temperature microscopic (100 nm resolution) surface photovoltage spectra of three CdSe/ZnCdMgSe quantum dot structures with different CdSe deposition times. Observed spectroscopic features were attributed to absorption in the barrier, quantum dot, and wetting layer. Good agreement with photoluminescence measurements was observed. Our results indicate that photogenerated carriers are confined within large quantum dots, but for small quantum dots there is significant tunneling of photogenerated holes to surface states. Our study shows that surface photovoltage spectroscopy is a useful tool for studying carrier tunneling and vertical coupling between quantum dots.