INVESTIGATION OF EPITAXIAL P-P CDTE HG0.775CD0.225TE HETEROJUNCTIONS BY CAPACITANCE-VOLTAGE PROFILING/

We investigate the electrical properties of isotype P-p CdTe/Hg0.775Cd 0.225Te heterojunctions grown in situ by the metalorganic chemical vap or deposition technique. The capacitance-voltage (C-V) characterizatio n of Schottky barriers (SE) is used to study the apparent majority car rier distribution and the valence band discontinuity. The C-V characte ristics of metal insulator semiconductor (MIS) devices were used to de termine the interface charge density. A theoretical model suitable for analysis of graded heterojunctions was developed based on the numeric al solution of Poisson's equation. The model includes an approximate d escription of the conduction band nonparabolicity and carrier degenera cy, We describe the procedures used in crystal growth and device fabri cation for both SE and MIS structures. We demonstrated, on the basis o f experimental measurements and theoretical analysis, that the valence band discontinuity in the devices studied here was 0.15 +/- 0.05 eV a nd the fixed interface charge density was approximately (3 +/- 1) . 10 (10) cm(-2). Also, we observed a dependence of the C-V measurements on temperature which seems to be caused by either interface traps or car rier inversion at the CdTe/HgCdTe interface.