Low-frequency admittance measurements on the HgCdTe/Photox SiO2 interface

Abstract

The complex admittance of an n-type Hg1−xCdxTe/Photox SiO2 interface with x=0.3 has been examined for frequencies ranging between 1 mHz and 4 MHz. The conductance method is used to decompose the total interface state density into three types of components: a valence-band tail, a conduction-band tail, and some well-resolved discrete states. The fixed charge density is low and there is no statistical broadening. The surface valence- and conduction-band edges are both found to be shifted upward in energy relative to their respective bulk values; moreover, the surface has converted to p type. The energy variation of the valence-band tail states response times follows a pattern characteristic of Shockley–Read recombination centers with a constant capture cross section, but the behavior of the conduction-band tail states is more complicated. Evidence is presented that the interface region has a higher Cd concentration than the bulk.