Microstructure of Ti/Al and Ti/Al/Ni/Au Ohmic contacts for {ital n}-GaN
- Materials Sciences Division, Lawrence Berkeley National Laboratory, University of California, MS 62-203, Berkeley, California 94720 (United States)
- Department of Materials Science and Mineral Engineering, University of California at Berkeley, Berkeley, California 94720 (United States)
- Materials Research Laboratory and Coordinated Science Laboratory, University of Illinois, Urbana-Champaign, Illinois 61810 (United States)
Transmission electron microscopy has been applied to characterize the structure of Ti/Al and Ti/Al/Ni/Au Ohmic contacts on {ital n}-type GaN ({approximately}10{sup 17} cm{sup {minus}3}) epitaxial layers. The metals were deposited either by conventional electron-beam or thermal evaporation techniques, and then thermally annealed at 900{degree}C for 30 s in a N{sub 2} atmosphere. Before metal deposition, the GaN surface was treated by reactive ion etching. A thin polycrystalline cubic TiN layer epitaxially matched to the (0001) GaN surface was detected at the interface with the GaN substrate. This layer was studied in detail by electron diffraction and high resolution electron microscopy. The orientation relationship between the cubic TiN and the GaN was found to be: {l_brace}111{r_brace}{sub TiN}//{l_brace}00.1{r_brace}{sub GaN}, [110]{sub TiN}//[11.0]{sub GaN}, [112]{sub TiN}//[10.0]{sub GaN}. The formation of this cubic TiN layer results in an excess of N vacancies in the GaN close to the interface which is considered to be the reason for the low resistance of the contact. {copyright} {ital 1996 American Institute of Physics.}
- Research Organization:
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 383086
- Journal Information:
- Applied Physics Letters, Vol. 69, Issue 11; Other Information: PBD: Sep 1996
- Country of Publication:
- United States
- Language:
- English
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