Electrical and structural characterisation of Ni/Ge/n-GaAs interface

The structural and electrical behaviour of Ni/Ge layers deposited onto n-type GaAs by electron beam evaporation were studied. The samples have been annealed for 20 min at different temperatures in flowing forming gas-H-2:N-2 (5%:95%)-in a tube furnace. When the annealing temperature was increased the Schottky barrier heights calculated from I-V and C-V characteristics decreased, and the I-V characteristics of the samples heat treated at 600 degrees C became linear. The contact resistance of the samples with linear characteristic was measured with Cox method. The calculated specific resistivity was 4.4 x 10(-4) ohmcm(2) in the case of sample heat treated at 550 degrees C and 5.1 x 10(-5) ohmcm(2) after annealing at 600 degrees C. In the sample annealed at 550 degrees C protrusions appeared with the size of 20-30 nm at the interface of semiconductor-metal. Detectable amount of Ge was found in addition to Ni, As, and G in the protrusions. Moreover, those features contain significantly less Ga than As. The protrusions containing Ge play a role in the formation of the low barrier contact. (C) 1998 Elsevier Science Ltd. All rights reserved.