Admittance dispersion of n-type GaAs/Ga(As, N)/GaAs heterostructures grownby molecular beam epitaxy

The electrical admittance of rectifying metal-semiconductor contacts on n-t ype GaAs/Ga(As, N)/GaAs heterostructures depends strongly on frequency and temperature. The distinct dispersion is due to the relatively high diffusio n barrier around the Ga(As, N) layer. As long as the admittance is controll ed by electrons inside the Ga(As, N) layer, their response to the ac electr ic field is dependent on frequency and temperature. Under appropriate condi tions, capacitance-voltage measurements can be used to examine depth-resolv ed electrical characteristics of n-type GaAs/Ga(As, N)/GaAs heterostructure s. The experimental depth profiles of the carrier concentration are compare d with calculations based on self-consistent solutions of the Poisson equat ion. For 3% GaN mole fraction, the conduction band offset between GaAs and Ga(As, N) is found to be -(0.40 +/-0.01) eV, i.e., about 95% of the total b and gap difference. The heterointerfaces are of type I. At the Ga(As, N)-on -GaAs interface, negative charges of about 1.3x10(11) cm(-2) are observed, which are not removed by postgrowth annealing. The as-grown GaAs-on-Ga(As, N) interface is free of fixed charges. However, acceptor-like interfacial t raps are generated at this interface by annealing, probably due to the conv ersion of those donor-like levels, which were detected at the inverted inte rface of as-grown p-type GaAs/Ga(As, N)/GaAs heterostructures. (C) 2001 Ame rican Institute of Physics.