Effects of surface treatment using aqua regia solution on the change of surface band bending of p-type GaN

• Published in: Journal of electronic materials 2001-03, Vol.30 (3), p.129-133
• Main Authors: JONG KYU KIM, KIM, Ki-Jeong, KIM, Bongsoo, JAE NAM KIM, JOON SEOP KWAK, YONG JO PARK, LEE, Jong-Lam
• Format: Article
• Language: English
• Subjects: Clean metal, semiconductor, and insulator surfaces; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Contact resistance, contact potential; Electron and ion emission by liquids and solids; impact phenomena; Electronic structure and electrical properties of surfaces, interfaces, thin films and low-dimensional structures; Electronic transport in interface structures; Exact sciences and technology; Photoemission and photoelectron spectra; Physics; Surface and interface electron states; Surface states, band structure, electron density of states
• ISSN: 0361-5235; 1543-186X
• DOI: 10.1007/s11664-001-0005-3

Effects of surface treatment on the change of band bending at the surface of p-type GaN were studied using synchrotron radiation photoemission spectroscopy, and the results were used to interpret the reduction of contact resistivity by the surface treatment. The contact resistivity on p-type GaN decreased from (5.1 plus or minus 1.2)x10 super(-1) to (9.3 sub( plus or minus )3.5) x 10 super(-5) Omega cm super(2) by the surface treatment using aqua regia prior to Pt deposition. Surface band bending was reduced by 0.58 eV and 0.87 eV after the surface treatments by HCl and aqua regia solutions, respectively. The atomic ratio of Ga/N decreased as the photoelectron detection angle was decreased, indicating that the surface oxide was mainly composed of Ga and O, GaO sub(x), formed during high-temperature annealing for the generation of holes, and Ga vacancies, V sub(Ga), were produced below the GaO sub(x) layer. Consequently, the aqua regia treatment plays a role in removing GaO sub(x) formed on p-type GaN, leading to the shift of the Fermi level toward the energy levels of V sub(Ga) located near the valence band edge. This causes the decrease of barrier height for the transport of holes, resulting in the good ohmic contacts to p-type GaN.