Ohmic contacts and schottky barriers to n-GaN

Authors: Fan, Z.; Mohammad, S.; Kim, W.; Aktas, Ö.; Botchkarev, A.; Suzue, K.; Morkoc, H.; Duxstad, K.; Haller, E.

Source: Journal of Electronic Materials, Volume 25, Number 11, November 1996 , pp. 1703-1708(6)

Publisher: Springer

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Abstract:

Gallium nitride is a highly promising wide bandgap semiconductor with applications in high power electronic devices and optoelectronic devices. For these devices to be realized, metallization, both ohmic and rectifying must be available. In this manuscript, we discuss the properties of ohmic contacts and Schottky barriers on n-type GaN. The most recent ohmic metallization scheme involves TV Al based composites, namely Ti/Al/Ni/Au (150Å/2200Å/400Å/500Å) preceded by a reactive ion etching (RIE) process which most likely renders the surface highly n-type. With annealing at 900°C for 30 s, contacts with specific resistivity values less than p_s= 1 x 10^-7 Ω cm² for a doping level of 4 x 10¹⁷ cm^-3 were obtained. Schottky barriers with Ti, Cr, Pd, Au, Ni, and Pt have been reported; however, we will concentrate here on Pt based structures as they yield a large barrier height of 1.1 eV. Both capacitance-voltage and current-voltage analyses have been carried out as a function of temperature to gain insight into the current conduction processes involved. Attention must now be turned to the modifications needed to render these contacts reliable.

Keywords: GaN; Ohmic contacts; Schottky barriers; Ti/Al/Ni/Au

Document Type: Research article

DOI: http://dx.doi.org/10.1007/s11664-996-0025-0

Publication date: 1996-11-01