The effect of subband quantization in the 2-D electron gas on thermionic current and heterojunction capacitance in an n-Al Ga1−As/n-GaAs heterojunction

The partition of the applied voltage between both sides of an n-AlGaAs/n-GaAs heterojunction is calculated, considering energy subband quantization in the very narrow triangular-like well in the GaAs and is used to calculate the thermionic current and the heterojunction capacitance as functions of the applied voltage. Comparison with classical calculations shows a difference of a few orders of magnitude in the current, especially in reverse bias, and a small difference in capacitance. By applying the model to self capacitance measured on heterojunction devices bounded with ohmic contacts on both sides, it is also shown how to obtain such parameters as conduction band discontinuity, doping in the AlGaAs, average distance of 2-D electron gas from the heterojunction, and sheet concentration. Experimental results using this method are within 10% of other recent determination of ΔEc.