High-permittivity dielectric stack on gallium nitride formed by silane surface passivation and metal-organic chemical vapor deposition

Abstract

We report the first demonstration of an in situ surface-passivation technology for a GaN substrate using vacuum anneal (VA) and silane (SiH4) treatment in a metal-organic chemical vapor deposition multichamber tool. Excellent electrical properties were obtained for TaN/HfAlO/GaN capacitors. Interface state density Dit was measured from midgap to nearconduction-band edge (EC) using the conductance method at high temperatures, and the lowest Dit of 1 × 1011 cm-2 * eV-1 at the midgap was achieved. Multiple frequency capacitance-voltage (C-V )measurement (10, 400, and 500 kHz) showed little frequency dispersion. Furthermore, the TaN/HfAlO/GaN stack was studied using high-resolution transmission electron microscopy, and the effectiveness of passivation using VA and SiH4 was evaluated using high-resolution X-ray photoelectron spectroscopy. The method reported here effectively removes the native oxide and passivates the GaN surface during the high-k dielectric-deposition process. © 2006 IEEE.