Reliability of discrete MODFETs: life testing, radiation effects, and ESD

Experimental and theoretical results of a reliability study of GaAs/AlGaAs MODFETs are presented and show a commonality of degradation modes under various accelerated stress conditions. The reliability of submicron-gate low-noise MODFETs was evaluated using high-temperature storage and DC operating life tests; significantly greater drain current degradation that occurred under DC bias is related to a field-assisted channel doping mechanism. Under pulsed electron irradiation long-term drain current transients were observed as well as persistent photoconductivity in some devices. Electrostatic-discharge experiments revealed that, unlike standard FETs, human body model (HBM) stressing of MODFETs results in loss of drain current, indicating deconfinement of the two-dimensional electron gas. The unified model of MODFET degradation is therefore related to field-assisted migration of alloy constituents and doping species.<>