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The degradation mechanisms of the noise characteristics of InGaP-gated low-noise pseudomorphic high-electron mobility transistors (PHEMTs) under accelerated stresses through dc and thermal stresses are investigated. The devices used were metal-organic chemical vapor deposition-grown In0.49Ga0.51P/In0.15Ga0.85As/GaAs low noise PHEMT structures with the gate dimensions of 0.25×160 μm2. The key noise/effect parameters of devices including 1) related to the deep-trap behavior in device, 2) source/gate resistances, and 3) gate to source capacitance and intrinsic transconductance are discussed. Based on the dc characteristics under dc and thermal stresses, the variations of the current-voltage curve, the diode characteristics (Schottky gate) with related trapping/detrapping phenomena induced by impact ionization and the variation of the depletion in gate-drain region are also investigated. The high reliability of InGaP low noise PHEMTs is demonstrated by the extremely small variations of the minimum noise figure and the associated power gain at 12 GHz after dc and thermal stresses.
Date of Publication: Aug. 2005