Failure Mechanisms in GaN HFETs under Accelerated RF Stress

A.M. Conway, M. Chen, P. Hashimoto, P.J. Willadsen, and M. Micovic

HRL Laboratories, LLC
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Keywords: GaN, HFET, reliability, life test, failure mechanisms Abstract

This work reports the results of the comprehensive three temperature accelerated RF life test on GaN HFETs at 10 Ghz. An activation energy of 1.8 eV was extracted giving a MTTF at Tch = 125 0C of 3.5x109 hours. Electrical characterization and cross sectional TEM were performed on devices that gracefully reached failure criteria. No visible evidence of gate sinking or electro migration was observed. Pulsed I-V measurements show an increase in “current slump” phenomena most likely caused by an increase in surface states between the gate and drain was the main cause of device failure. FIB/TEM was also performed on devices stressed in air which show feature on drain edge of gate in the AlGaN barrier layer. EELS maps show increased oxygen levels in the defect region.

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