BAND OFFSETS IN SEMICONDUCTOR HETEROJUNCTIONS

This chapter presents an overview of several theoretical approaches and experimental measurement techniques for determining band offset values and discuss the experimental and theoretical data reported for a number of specific heterojunction systems. It also evaluates the credibility and accuracy of the experimental measurements and provides a tabulation of reliable band offset values for as many heterojunctions as possible. Among the most important physical parameters for a given heterojunction system are the conduction- and valence-band offsets; indeed, the quality and even the feasibility of heterojunction device concepts often depend crucially on the values of these band offsets. The band offset is defined simply as the discontinuity in the band edge at the interface between two semiconductors. A number of current theories seem to yield band offset values in reasonable agreement with experiment, even though the physical ideas underlying these theories can be quite different. These ideas include electron affinities, Schottky barrier heights, bulk band structures on the same energy scale, and the definition of effective midgap energies corresponding to charge neutrality for each bulk constituent. © 1992, Academic Press, Inc. All rights reserved.