Optimization of ohmic contact for InP-based transferred electronic devices

The effect of the annealing time and annealing temperature on Ni/Ge/Au electrode contacts deposited on the n-type InP contact layer has been studied using a circular transmission line model. The minimum specific contact resistance of 3.2 x 10(-7) Omega center dot cm(2) was achieved on the low-doped n-type InP contact layer with a 40 s anneal at 425 degrees C. In order to improve the ohmic contact and reduce the difficulty in the fabrication of the high doped InP epi-layer, the doping concentration in the InP contact layer was chosen to be 5 x 10(-18) cm(-3) in the fabrication of transferred electronic devices. Excellent differential negative resistance properties were obtained by an electron beam evaporating the Ni/Ge/Au/Ge/Ni/Au composite electrode on an InP epi-layer with a 60 s anneal at 380 degrees C.