Improved low resistance contacts of Ni/Au and Pd/Au to p-type GaN using a cryogenic treatment
A low resistance Ohmic contact to p-type GaN is essential for reliable operation of electronic and optoelectronic devices. Such contacts have been made using Ni/Au and Pd/Au contacts to p-type Mg-doped GaN (1.41x10{sup 17}cm{sup {minus}3}) grown by metalorganic chemical vapor deposition (MOCVD) on (0001) sapphire substrates. Thermal evaporation was used for the deposition of those metals followed by annealing at temperatures of 400 {approximately} 700 C in an oxygen and nitrogen mixed gas ambient, then subsequently cooled in liquid nitrogen which reduced the specific contact resistance from the range of 9.46{approximately}2.80x10{sup {minus}2} {Omega}cm{sup 2} to 9.84{approximately}2.65x10{sup {minus}4} {Omega}cm{sup 2} for Ni/Au and from the range of 8.35{approximately}5.01x10{sup {minus}4} {Omega}cm{sup 2} to 3.34{approximately}1.80x10{sup {minus}4} {Omega}cm{sup 2} for Pd/Au. The electrical characteristics for the contacts were examined by the current versus voltage curves and the specific contact resistance was determined by use of the circular transmission line method (c-TLM). The effects of the cryogenic process on improving Ohmic behavior (I-V linearity) and reducing the specific contact resistance will be discussed from a microstructural analysis which reveals the metallurgy of Ohmic contact formation.
- Research Organization:
- State Univ. of New York at Buffalo, Amherst, NY (US)
- OSTI ID:
- 20104636
- Country of Publication:
- United States
- Language:
- English
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