Characterization of low-resistance ohmic contacts to heavily carbon-doped n-type InGaAsBi films treated by rapid thermal annealing*

Abstract

Carbon-doped InGaAsBi films on InP:Fe (100) substrates have been grown by gas source molecular beam epitaxy (GSMBE). The electrical properties and non-alloyed Ti/Pt/Au contact resistance of n-type carbon-doped InGaAsBi films were characterized by Van der Pauw–Hall measurement and transmission line method (TLM) with and without rapid thermal annealing (RTA). It was found that the specific contact resistance decreases gradually with the increase of carrier concentration. The electron concentration exhibits a sharp increase, and the specific contact resistance shows a noticeable reduction after RTA. With RTA, the InGaAsBi film grown under CBr4 supply pressure of 0.18 Torr exhibited a high electron concentration of 1.6 × 1021 cm−3 and achieved an ultra-low specific contact resistance of 1 × 10−8 Ω⋅cm2, revealing that contact resistance depends greatly on the tunneling effect.