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-all oyed ohmic contact to GaAs-based devices is discussed. Very low specific co ntact resistance of 10(-7) Omega cm(2) was measured using conventional Ni/A uGe/Ni/Au metal contact system. A theoretical model for tunnelling through metal-semiconductor barriers using the WKB approximation was developed whic h indicates a good agreement with experimental data. HBTs fabricate using t hese InGaAs capping layers demonstrated very low emitter series resistance, up to four times smaller compared to similar HBT structures using GaAs cap ping layers. (C) 1999 Elsevier Science S.A. All rights reserved.