Contact property of Ni(Ti)/Pt/Au on p-In0.52Al0.48As

The annealing effects of rapid thermal processing in N2 from 350 °C to 500 °C for 60 s on Ni/Pt/Au contacts to p-InAlAs have been investigated. The result indicated that the contacts were all Schottky contacts and lowest barrier height(0.67eV) was achieved at about 450 °C. Then we used evacuated sealed-ampoule Zn diffusion method to form a heavily doped layer on p-InAlAs layer of the same sample. The diffusion conditions were 530 °C &4 min and 530 °C &8 min, respectively. Also Ni/Pt/Au contacts were deposited on the two samples and annealed at 450 °C &60 s. Although I-V characteristics which were measured indicated that a heavily doped layer is beneficial for the cantacts properties, the contacts were still Schottky contacts and the barrier heights were reduced to 0.54 eV and 0.57 eV for the two samples. Finally, we investigated contacts property of Ti/Pt/Au on p-In0.52Al0.48As of the sample which is Zn-diffused at 530 °C for 4 min. The sample was annealed at 450 °C for 60 s and the contact resistivity of the contacts was determined using the transfer line model measurements. Low resistance ohmic contacts (ρ c =8.88×10 -4 Ωcm 2 ) were achieved. The results indicated that the contacts property is controlled by chemical and metallurgical reaction between the contact metal and the InAlAs layer, and a heavily doped layer is beneficial to contact properties.