Reliability study of gallium arsenide transistors

GaAs signal transistors of the MESFET and HEMT (high electron mobility transistor) technologies were evaluated in an accelerated life test to determine their reliability for space-borne applications. It was found that GaAs MESFET technology is sufficiently mature and reliable for space systems, but that the GaAs HEMT technology is not. Secondary electron and source current imaging of an NE 202 HEMT which had failed during life testing show a bright spot indicating a subsurface defect. The effect of this defect is to short the transistor so that it cannot be turned off. It is concluded that the subsurface defect causing failure in the NE 202 HEMT was either a latent defect present originally in the GaAs material or created during the aging test by the thermal runaway/bridging phenomenon.<
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