HOT-CARRIER EFFECTS IN ALGAAS INGAAS HIGH-ELECTRON-MOBILITY TRANSISTORS - FAILURE MECHANISMS INDUCED BY HOT-CARRIER TESTING/

A new failure mechanism of AlGaAs/InGaAs pseudomorphic high electron m obility transistors has been observed after hot carrier de accelerated testing. Hot carrier effects have been characterized by means of gate current measurements and electroluminescence spectroscopy. After acce lerated testing, a permanent degradation has been found, consisting of the decrease of drain current I-D, and of the absolute value of the p inch-off voltage V-p, at low drain-source voltage V-DS, resulting in t he development of a remarkable ''kink'' in the output characteristics. Direct current, pulsed, and low-frequency ac measurements demonstrate that the failure mechanism consists of the creation of deep levels un der the gate which act as electron traps at low gate-to-drain electric fields. Deep level transient spectroscopy and photoinjection measurem ents reveal the presence of two levels at 0.77 eV and 1.22 eV. The int ensity of the 1.22 eV peak is correlated with the degradation observed in stressed devices. (C) 1997 American Institute of Physics.