Scanning Electron Microscope Studies of Premature Breakdown Sites in GaAs IMPATT Testers

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Abstract
Premature breakdown sites in Pt‐GaAs IMPATT test diodes were examined with the scanning electron microscope operating in the electron beam induced current mode. Studies were made on mesa and planar structures, with and without air aging up to 350°C. The main conclusions of these studies are that (i) premature breakdown occurs primarily at sites of metallization defects and roughness around the periphery of the diodes; (ii) diode degradation and the lowering of the breakdown voltage following air aging is manifested at sites at the edge of the metallization; and (iii) very small sites of missing metallization (“pinholes”) are sites of diode breakdown.