Small-signal field effect in GaAs/InAs quantum-dot heterostructures

Abstract

InAs quantum dots (QDs), incorporated into the space-charge region of an epitaxial n-GaAs film at different distances (5–300 nm) from the surface, decrease the potential barrier for the electrons located in n-GaAs. For tunnel-thin coating layers this decrease is related to tunneling through QD energy levels. For thick layers this decrease is caused by negative charging of the QDlevels and defects located near QDs. The decrease in the barrier increases the efficiency of electron capture by surface states and shifts the frequency dispersion of mobility under the field effect, related to this capture, toward higher frequencies. When QDs are incorporated near the barrier’s base, they manifest themselves in the relaxation of the small-signal field effect. Some parameters of the QD levels are determined. Defect formation is revealed in the layers adjacent to QDs.