Indexed on: 06 Feb '15Published on: 06 Feb '15Published in: Applied Physics A
Pd/In/Ni/Au contacts to N-polar n-GaN were investigated to obtain low contact resistance and high thermal stability contacts. Two-step thermal annealing method was developed to form the PdIn and InGaN alloys successively, which were clarified by Auger electron spectroscopy and transmission electron microscopy measurements. The lowest specific contact resistivity was achieved as 5.4 × 10−5 Ω cm2 when the sample was annealed under 250 °C for 600 s and 500 °C for 30 s in N2 ambient in sequence. It was observed that Pd/In fusion was occurred at the first annealing step. The PdIn alloy can well act as the blocking layer to prevent the outdiffusion of Ga atoms from n-GaN and low work function material as well. The second annealing step led to some content InGaN formation. PdIn contact to InGaN may get a small Schottky barrier height and some effective electron accumulation at the GaN/InGaN interface, which decreases the specific contact resistivity of Pd/In/Ni/Au to N-polar n-GaN.