Cross-sectional STM on superlattices and the effect of doping

The effect of semiconductor doping on the topography and spectroscopy in cross-sectional STM is discussed. The experimental work refers to the ultra-high-vacuum cleaved (110) plane of (001) MBE-grown Be-doped GaAs superlattices. The electronic signature of individual active dopant sites on the electronic charge density as well as the sensitivity to modulated doping are demonstrated. The doping density assigned from our STM experiments is compared with SIMS data. Furthermore, the effect of the doping density on the tunneling spectroscopy is investigated: the voltage-induced subsurface space-charge region has a profound effect on the observed current-voltage characteristics. © 1994.