An Au/Pt/Ti/WN/sub x/ ohmic contact to n-InGaAs and its application to AlGaAs/GaAs HBTs

We report the experiments that were performed to investigate the alloying temperature dependence of Au/Pt/Ti/WN/sub x/ ohmic contacts to n-InGaAs. Very low resistance contacts (10/sup -8//spl sim/10/sup -7/ /spl Omega/cm/sup 2/) were obtained after RTA at the temperatures from 250 to 450/spl deg/C. It was observed from XRD and AES analyses that there were no remarkable phase transformations for the contact system subjected to heat treatments. When Au/Pt/Ti/WN/sub x/ ohmic contacts were applied to AlGaAs/GaAs HBTs, moderate DC and RF performances were also achieved. It is believed that these ohmic schemes can be used as stable and low resistance contacts for high temperature HBT applications.