REDISTRIBUTION OF CONSTITUENT ELEMENTS IN PD GE CONTACTS TO N-TYPE GAAS USING RAPID THERMAL ANNEALING/

Pd/Ge contact to n-type GaAs is performed by using electron-beam evapo ration and rapid thermal annealing. The rapid thermal annealing is per formed at 400-500-degrees-C for various time durations. Low specific c ontact resistivity on the order of 10(-6) OMEGA CM2 is obtained from m easurements based on the transmission line model method. The contact d epth profiles are analyzed by secondary ion mass spectrometry (SIMS). A very shallow ohmic contact is achieved. The redistribution of consti tuent elements after heat treatment is examined. A gallium SIMS signal bump is detected in the contact layer and is correlated with good ohm ic contact behavior. A model based on Ga vacancies is proposed to expl ain this phenomenon. This shallow ohmic contact technology has been su ccessfully utilized to fabricate GaAs/AlGaAs and GaAs/InGaAs/AlGaAs ne gative resistance field-effect transistors, for which shallow ohmic co ntact is critical.