Gate-Length Dependence of Negative Differential Resistance in InGaAs/InAlAs Quantum Well Field-Effect Transistor

Abstract

We have investigated the gate-length dependence of negative differential resistance (NDR) in an InGaAs/InAlAs quantum well field-effect transistor (QW-FET) by varying the gate length from 50 nm to 0.8 µm. A pronounced N-shaped NDR is clearly observed in these QW-FETs. The gate leakage current is detectable only by the onset of NDR. We believe that the NDR should be attributed to the real space transfer of channel electrons into the barrier layer with low mobility underneath the gate by gate field-assisted tunneling (RSTT). Both peak-to-valley current ratio (PVR) and onset voltage (VNDR) are found to be strongly dependent on the gate length. The NDR characteristics in terms of PVR and VNDR are improved dramatically by reducing the gate length, and originate from the velocity overshoot due to the suppression of scattering probability.