The determination of heterojunction energy band discontinuities in the presence of interface states using capacitance-voltage techniques
- 15 November 1988
- journal article
- research article
- Published by AIP Publishing in Journal of Applied Physics
- Vol. 64 (10) , 5030-5040
- https://doi.org/10.1063/1.342456
Abstract
Effects of trapped interface charge on the determination of heterojunction energy band discontinuity energies using capacitance‐voltage (C‐V) techniques are analyzed both theoretically and experimentally. We show that for shallow traps, whose charge occupancy is unchanged by variations in the applied voltage, the measured conduction band discontinuity energy (ΔEc) as determined by the depletion technique [Kroemer, Chien, Harris, and Edwall, Appl. Phys Lett. 3 6, 295 (1980)] is a function of trap density (σi). This error source in determining ΔEc is large for small values of ΔEc due to distortions of the conduction band induced by the trapped interface charge. In addition, the analysis used for determining σi and ΔEc via the depletion technique has been generalized to correct for the effects of both deep and shallow traps. We show that at low measurement frequency, the measured value of ΔEc is nearly independent of σi, and this value is near to the exact value of ΔEc measured in the absence of interface traps (i.e., for σi=0). However, at high measurement frequency (or low temperature), the measured ΔEc decreases with increasing σi or increasing trap energy depth from the conduction band minimum. These deviations from the actual value can be corrected by using the equations developed in this article. We apply these results to the understanding of In0.53Ga0.47As/InP heterojunctions. The computer‐simulated apparent free carrier concentration profiles are used to fit experimental data at several temperatures. The best fit value of ΔEc (=0.22 eV) is in agreement with the value obtained via the emended equations. We explain the complex temperature dependence of these experimental profiles as due to donor traps near the heterojunction.This publication has 28 references indexed in Scilit:
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