Reliability testing of InP HEMT's using electrical stress methods

In this paper, we discuss the results of three different electrical stress tests on InP-based HEMT's and their implications toward reliability. These are hot electron (HE) stress, transmission line pulse (TLP) measurements, and RF overdrive stress. Some processing parameters have been varied to investigate their influence on reliability issues. HE stress is performed on a set of Si3N4 passivated devices with increasing recess width. Degradation is observed to be largely dependent on recess width, due to changes at the InAlAs-Si3N4 interface. With TLP measurements, an ESD-like reliability study is performed on devices with different types of Schottky barriers. Although epilayers with In0.40Al0.60 as Schottky material show improved breakdown and leakage characteristics over In0.52Al0.48As, pulsed stress tests reveal an earlier breakdown. Finally, the degradation under large-signal RF overdrive stress is determined with a nonlinear network measurement system (NNMS). Both on- and off-state degradation are studied with this set-up. Results appeared to be strongly dependent on the phase difference between the stress voltage waves applied at the device ports.