ISSN:
1089-7550
Source:
AIP Digital Archive
Topics:
Physics
Notes:
The microstructure of oxidized Ni/Au films on p-GaN was examined to elucidate the formation of a low resistance ohmic contact to p-GaN with a field-emission gun transmission electron microscope in conjunction with composition analyses. The p-GaN/Ni/Au samples were heat treated at 500 °C in air mainly composed of a mixture of crystalline NiO, Au, and amorphous Ni–Ga–O phases. Small voids adjacent to the p-GaN film were also observed. The as-deposited Au film converted into discontinuous islands containing small amounts of Ni that connect with p-GaN. NiO formed a continuous film at the surface that covers the Au islands and the amorphous Ni–Ga–O phases. Moreover, NiO partially contacts p-GaN as well as Au islands and the amorphous Ni–Ga–O phase. The orientation relationship of the crystalline NiO, Au-rich islands, and p-GaN film was identified as NiO(111)//Au(111¯)//GaN(0002) and NiO[11¯0]//Au[11¯0]//GaN[112¯0]. The results suggested that Ni atoms diffuse through the Au layer onto the surface and react with oxygen to form NiO, whereas Au atoms diffuse towards the inside to form a Au–Ni alloy. The microstructural examination indicated that the crystalline NiO and/or the amorphous Ni–Ga–O phases may significantly affect the low resistance ohmic contact to p-GaN. © 1999 American Institute of Physics.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.371294
