Failure Mechanisms and Reliability of Low-Noise GaAs FETs

This paper describes the goals, experimental methods, and results of a study of the reliability of low-noise gallium arsenide field-effect transistors 1 involving about 1500 devices and 1.5 million device-hours of aging. The ultimate purpose of this work is twofold: (i) to calculate LOW-NOISE GaAs FETs 2823 the probable failure rate as a function of time; (ii) to identify the failure and degradation mechanisms and propose corrective action where possible. To estimate the failure rate of the device for any given operational conditions, each of these mechanisms should be characterized in terms of the nature of its cumulative failure distribution, the median life and standard deviation of the distribution, and the activation energy of the mechanism. Since the reliability of a GaAs FET depends intimately on its structural details, especially the choice of metallization, the structure of the devices studied is described in Section II of this report. The various acceleration methods, measurement techniques, and other aspects of the experimental program will be discussed in Section III. The failure modes observed may be categorized as either sudden or gradual. The former are marked by a complete collapse of dc and RF properties and are almost always associated with a failure of the gate metallization. They are the subject of Section IV. (Burn-out due to undesirable voltage pulses is considered a matter of handling technique or circuit design and is not investigated in the present work.) The gradual failures involve degradation of the important RF properties, especially the noise figure and the gain.