A Ti(12 nm)/W(20 nm)/Au(50 nm) metallization scheme has been investigated for obtaining thermally stable low-resistance ohmic contacts to n-type GaN (4.0×1018 cm-3). It is shown that the current-voltage (I-V) characteristics of the samples are abnormally dependent on the annealing temperature. For example, the samples that were annealed at temperatures below 750 °C for 1 min in a N2 ambient show rectifying behavior. However, annealing the samples at temperatures in excess of 850 °C results in linear I-V characteristics. The contact produces a specific contact resistance as low as 8.4×10-6 Ω∈cm2 when annealed at 900 °C. It is further shown that the contacts are fairly thermally stable even after annealing at 900 °C; annealing the samples at 900 °C for 30 min causes insignificant degradation of the electrical and structural properties. Based on glancing angle X-ray diffraction and Auger electron microscopy results, the abnormal temperature dependence of the ohmic behavior is described and discussed.
|Number of pages||4|
|Journal||Applied Physics A: Materials Science and Processing|
|Publication status||Published - 2005 Aug|
ASJC Scopus subject areas
- Materials Science(all)