Extremely Low Resistance Ohmic Contacts to n-GaAs for AlGaAs/GaAs Heterojunction Bipolar Transistors

Abstract

New AuGe/Ni/Ti/Au multi-layer structure ohmic contact to n-GaAs is reported which is suitable to fabricate fine emitter and collector patterns of AlGaAs/GaAs heterojunction bipolar transistors. According to an Auger electron spectroscopy investigation, a new alloying mechanism takes place in reducing contact resistivity. A contact resistivity of 3×10 -7 Ω·cm 2 for 3×10 18 cm -3 doped n-GaAs was achieved through optimum alloying at 370°C.