Non-alloyed ohmic contacts using MOCVD grown n+-InxGa1−xAs on n-GaAs

The use of MOCVD grown n+-InxGa1−xAs capping layer to produce a non-alloyed ohmic contact to GaAs-based devices is discussed. Very low specific contact resistance of 10−7 Ω cm2 was measured using conventional Ni/AuGe/Ni/Au metal contact system. A theoretical model for tunnelling through metal-semiconductor barriers using the WKB approximation was developed which indicates a good agreement with experimental data. HBTs fabricate using these InGaAs capping layers demonstrated very low emitter series resistance, up to four times smaller compared to similar HBT structures using GaAs capping layers.