Device reliability study of high gate electric field effects in AlGaN/GaN high electron mobility transistors using low frequency noise spectroscopy

Abstract

Low frequency noise characteristics of gate and drain currents are investigated for prestressed and poststressed AlGaN/GaN high electron mobility transistors. High reverse bias voltage stresses on the gate stack changes both drain and gate current noise. A temporary increase in drain current noise was observed during stress which recovered to prestress level a few weeks later. This is explained via a positive and negative threshold voltage shift due to electron trapping under the gate during and after stress, respectively. On the other hand, gate current noise shows a permanent increase after the stress which is not seen to recover once the stress is removed. It is proposed that new defect states are created below the metal AlGaN layer of the gate edges which leads to a permanent degradation of gate current noise.