Negative transconductance and negative differential resistance in a grid-gate modulation-doped field-effect transistor

Abstract

We report on transport measurements in grid-gate lateral-surface-superlattice (LSSL) field-effect transistors on a modulation-doped GaAs/AlGaAs heterostructure. The LSSL is created by a 0.2 μm period Ti/Au grid on top of the AlGaAs layer, which presents a tunable, two-dimensional periodic potential modulation to the electrons traveling from source to drain. Current measurements at 4.2 K as a function of gate bias exhibit negative transconductance at a fixed drain bias below 15 mV, providing evidence of a superlattice effect (i.e., coherent back-diffraction). In addition, negative differential resistance is observed at a fixed gate bias and a drain bias around 100 mV, which could be a manifestation of sequential resonant tunneling.