Numerical simulation of the response of substrate traps to a voltage applied to the gate of a gallium arsenide field effect transistor

Abstract

Wereportonanumericalsimulationoftheresponseofsubstratetrapstoavoltage appliedtothegateofagalliumarsenidefieldeffecttransistor(GaAsFET)using proprietary simulationsoftware.Thesubstrateisassumedtocontainshallowacceptors compensatedbydeeplevels.Theratiobetweenthedensitiesofdeepandshallowlevelsis consideredtobeonehundred,whichisatypicalvalueforsemi-insulatingsubstrates. Althoughseveraltrapsmaybepresentinthesubstratebutonlythemostcommonly observedonesareconsidered,namelyholetrapsrelatedtoCuandCr,andthefamiliar native electrontrapEL2.Thecurrent–voltagecharacteristicsoftheGaAsFETarecalculated in theabsenceaswellasinthepresenceoftheabovementionedtraps.Itwasfoundthat the holetrapsareaffectedbythegatevoltagewhiletheelectrontrapisnot.Thiseffecton the responseofholetrapsisexplainedbythefactthatthequasi-holeFermilevelinthe substrateisdependentonthegatevoltage.However,theelectronquasi-Fermilevelinthe substrateisinsensitivetothegatevoltageandthereforeelectrontrapsarenotperturbed.