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

• Published in: Journal of applied physics 2001-09, Vol.90 (5), p.2405-2410
• Main Authors: Krispin, P., Spruytte, S. G., Harris, J. S., Ploog, K. H.
• Format: Article
• Language: English
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/1.1391218

The electrical admittance of rectifying metal–semiconductor contacts on n-type GaAs/Ga(As, N)/GaAs heterostructures depends strongly on frequency and temperature. The distinct dispersion is due to the relatively high diffusion barrier around the Ga(As, N) layer. As long as the admittance is controlled by electrons inside the Ga(As, N) layer, their response to the ac electric field is dependent on frequency and temperature. Under appropriate conditions, capacitance–voltage measurements can be used to examine depth-resolved electrical characteristics of n-type GaAs/Ga(As, N)/GaAs heterostructures. The experimental depth profiles of the carrier concentration are compared with calculations based on self-consistent solutions of the Poisson equation. 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 band gap difference. The heterointerfaces are of type I. At the Ga(As, N)-on-GaAs interface, negative charges of about 1.3×1011 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 traps are generated at this interface by annealing, probably due to the conversion of those donor-like levels, which were detected at the inverted interface of as-grown p-type GaAs/Ga(As, N)/GaAs heterostructures.