I-V-T measurements on GaAs/AlGaAs heterojunctions interpreted on the basisof thermally assisted tunneling

I-V-T data is routinely used to determine the conduction band discontinuity in heterojunction structures. In the present paper, capacitance-voltage an d current-voltage-temperature measurements performed on AlGaAs/GaAs isotype heterojunctions are presented and analysed over a wide temperature range ( 77 K-300 K). Considering thermionic emission alone when analysing I-V-T dat a resulted in several problems. The Richardson plot [In(J(o)/T-2) vs. 1/T], in particular while suggesting that the thermally activated process is of importance in the overall conduction mechanism, shows two distinct linear r egions of different slope over two temperature ranges. Also the derived act ivation energies and hence the band discontinuity from I-V-T data is very m uch lower than the value obtained from C-V profiling which is in very good agreement with values routinely published in literature. However, the resul ts obtained from both I-V-T and C-V data are reconciled when considering a simple analytical expression for the current based on the assumption that t hermally assisted tunneling is the dominant current generating mechanism ov er most of the temperature range.