Mechanisms of a negative differential conductivity in a short-channel In0.52Ga0.48As/In0.53Al0.47As HEMT

The effect of negative resistivity observed at anomalously low voltages in output characteristics of modulation-doped In0.53Ga0.47As/In0.52Al0.48As field-effect transistors is considered. In the discussed experiments, the threshold for appearance of negative resistivity depends not only on the gate length, which was mentioned before, but also on the gate-drain voltage. It is shown that the negative differential resistivity observed at output characteristics of the short-channel In0.53Ga0.47As/In0.52Al0.48As field-effect transistor at anomalously low threshold voltages is related to the formation of the second transport channel. This effect is a result of resonance transition of hot electrons from upper levels of the quantum well to the above-barrier layer via the states of ionized donor impurity.