An ab initio-based approach to phase diagram calculations for GaN(0 0 0 1) surfaces

✍ Scribed by Tomonori Ito; Tomoyuki Nakamura; Toru Akiyama; Kohji Nakamura

• Publisher: Elsevier Science
• Year: 2008
• Tongue: English
• Weight: 383 KB
• Volume: 254
• Category: Article
• ISSN: 0169-4332
• DOI: 10.1016/j.apsusc.2008.01.129

✦ Synopsis

Surface phase diagrams of GaN(0 0 0 1)-(2 Â 2) and pseudo-(1 Â 1) surfaces are systematically investigated by using our ab initio-based approach. The phase diagrams are obtained as functions of temperature T and Ga beam equivalent pressure p Ga by comparing chemical potentials of Ga atom in the vapor phase with that on the surface. The calculated results imply that the (2 Â 2) surface is stable in the temperature range of 700-1000 K at 10 À8 Torr and 900-1400 K at 10 À2 Torr. This is consistent with experimental stable temperature range for the (2 Â 2). On the other hand, the pseudo-(1 Â 1) phase is stable in the temperature range less than 700 K at 10 À8 Torr and less than 1000 K at 10 À2 Torr. Furthermore, the stable region of the pseudo-(1 Â 1) phase almost coincides with that of the (2 Â 2) with excess Ga adatom. This suggests that Ga adsorption or desorption during GaN MBE growth can easily change the pseudo-(1 Â 1) to the (2 Â 2) with Ga adatom and vice versa.