Deep traps in GaAs revealed at high resolution by simple fast photocapacitance methods

Abstract

The characteristics of a new type of capacitance spectroscopy of deep traps in semiconductors are reviewed. A double radiation source technique is employed, the first source controlling the occupation of the traps and the characteristic time constant of the experiment, the second probing the spectral distribution of traps by selectively photoinducing emission to the conduction and valence bands. Time differentiation enhances the detectivity of the traps and minimizes drift problems. Typical spectra obtained with this quasi-equilibrium spectroscopic technique are described. The chromium trap in GaAs presents a distinctive feature with interesting properties which are discussed. Comparisons with thermal capacitance measurements are made, showing the complementary nature of the two methods. The use of the technique to detect out-diffusion of Cr from an insulating substrate into an epitaxial layer is described.