Microstructure, electrical properties, and thermal stability of Ti-based ohmic contacts to {ital n}-GaN
- Materials Research Center, North Carolina State University, Raleigh, North Carolina 27695-7919 (United States)
- Center for Solid State Science, Arizona State University, Tempe, Arizona 85287-1704 (United States)
Single Ti layers, single TiN layers, and thin Ti films overlayered with Au were investigated as ohmic contacts to {ital n}-type (n=4.5{times}10{sup 17} to 7.4{times}10{sup 18}&hthinsp;cm{sup {minus}3}) single-crystal GaN (0001) films. Transmission line measurements (TLM) revealed the as-deposited TiN and Au/Ti contacts on n=1.2{times}10{sup 18}&hthinsp;cm{sup {minus}3} to be ohmic with room-temperature specific contact resistivities of 650 and 2.5{times}10{sup {minus}5} {Omega} cm{sup 2} respectively. Single Ti layer contacts had high resistance and were weakly rectifying in the as-deposited condition. The three contact/GaN systems exhibited a substantial decrease in resistivity after annealing; the value of {rho}{sub c} was also a function of the carrier concentration in the GaN. The Au/Ti contacts exhibited the lowest resistivity values yet observed in these contact studies, particularly for the more lightly doped {ital n}-GaN. The {rho}{sub c} for n=1.2{times}10{sup 18}&hthinsp;cm{sup {minus}3} reached 1.2{times}10{sup {minus}6}&hthinsp;{Omega} cm{sup 2}; for n=4.5{times}10{sup 17}&hthinsp;cm{sup {minus}3}, {rho}{sub c}=7.5{times}10{sup {minus}5}&hthinsp;{Omega} cm{sup 2} after annealing both samples through 900&hthinsp;{degree}C. X-ray photoelectron spectroscopy (XPS) and high-resolution cross-sectional transmission electron microscopy (X-TEM) analysis revealed the formation of TiN at the interface of annealed Ti layers in contact with GaN, which is believed to be beneficial for ohmic contact performance on {ital n}-GaN. {copyright} {ital 1999 Materials Research Society.}
- OSTI ID:
- 341173
- Journal Information:
- Journal of Materials Research, Journal Name: Journal of Materials Research Journal Issue: 3 Vol. 14; ISSN JMREEE; ISSN 0884-2914
- Country of Publication:
- United States
- Language:
- English
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