We have sputter-deposited 500-1200 angstrom thick WSi0.45 and W metallization onto both n+ GaN (n = 1019 cm-3) doped either during MOCVD growth or by direct Si+ ion implantation (5 × 1015 cm-2, 100 keV) activated by RTA at 1400°C for 10 s and p+ (NA = 1018 cm-3) GaN. In the n-type epi samples Rc values of 10-4 Ω cm-2 were obtained and were stable to approx. 1000°C. The annealing treatments up to 600°C had little effect on the WSix/GaN interface, but the β-W2N phase formed between 700-800°C, concomitant with a strong reduction (approximately a factor of 2) in near-surface crystalline defects in the GaN. Spiking of the metallization down the threading and misfit dislocations was observed at 800°C, extending > 5000 angstrom in some cases. This can create junction shorting in bipolar or thyristor devices. Rc values of approx. 10MIN6 Ω cm-2 were obtained on the implanted samples for 950°C annealing, with values of approx. 10-5 Ω cm-2 after 1050°C anneals. On p-GaN, the contacts are essentially leaky Schottky diodes at 25°C, but became ohmic at ≥ 250°C, with Rc in the 10-2 Ω cm-2 range. The W-based metallization is much more thermally stable than the more common Ni/Au.
|Number of pages||4|
|Journal||Materials Science and Engineering B: Solid-State Materials for Advanced Technology|
|State||Published - 6 May 1999|
|Event||Proceedings of the 1998 Symposium L: on Nitrides and Related Wide Band Gap Materials (E-MRS Meeting) - Strasbourg|
Duration: 16 Jun 1998 → 19 Jun 1998