Semicond. Sci. Technol. 11, 475-482 (1996)

The influence of imperfections and weak disorder on domain formation in superlattices

G. Schwarz, A. Wacker, F. Prengel, and E. Schöll

Institut für Theoretische Physik, Technische Universität Berlin,
Hardenbergstrasse 36, 10623 Berlin, Germany

J. Kastrup, H. T. Grahn, and K. Ploog

Paul-Drude-Institut für Festkörperelektronik,
Hausvogteiplatz 5-7, 10117 Berlin, Germany

Abstract

The influence of imperfections and weak disorder on the vertical charge transport in semiconductor superlattices at high electric fields is investigated. We present numerical simulations of the stable high-field domain states and of the self-generated spatio-temporal current oscillations, and demonstrate that the current-voltage characteristics in the regime of domain formation are extremely sensitive to small amounts of disorder introduced by fluctuations of the well and barrier widths as well as the doping densities in the growth direction. Comparison with experiments shows that such fluctuations can explain the irregularity of the current branches observed in the measured characteristics. It is possible to identify the location of a single imperfection within the superlattice structure from the calculated current-voltage characteristics. Disorder also strongly affects the regime in which oscillatory current instabilities occur as well as the frequency and the mode of the oscillations. WE propose to use these investigations as a novel method to detect growth-related imperfections in a superlattice.

mail:schwarz@physik.tu-berlin.de

last update: May 31, 1996