Influence of V/III growth flux ratio on trap states in m-plane GaN grown by ammonia-based molecular beam epitaxy

• Published in: Applied physics letters 2012-10, Vol.101 (15)
• Main Authors: Zhang, Z., Hurni, C. A., Arehart, A. R., Speck, J. S., Ringel, S. A.
• Format: Article
• Language: English
• Subjects: ACTIVATION ENERGY; AMMONIA; CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; DEEP LEVEL TRANSIENT SPECTROSCOPY; Flux; GALLIUM NITRIDES; LAYERS; MOLECULAR BEAM EPITAXY; N-TYPE CONDUCTORS; OPTIMIZATION; Origins; OXYGEN; PHOTOLUMINESCENCE; SEMICONDUCTOR MATERIALS; SENSITIVITY; SPECTRA; Spectroscopy; TRAPS
• ISSN: 0003-6951; 1077-3118
• DOI: 10.1063/1.4759037

Deep level transient spectroscopy (DLTS) and deep level optical spectroscopy (DLOS) were utilized to investigate the behavior of deep states in m-plane, n-type GaN grown by ammonia-based molecular beam epitaxy (NH3-MBE) as a function of systematically varied V/III growth flux ratios. Levels were detected at EC − 0.14 eV, EC − 0.21 eV, EC − 0.26 eV, EC − 0.62 eV, EC − 0.67 eV, EC − 2.65 eV, and EC − 3.31 eV, with the concentrations of several traps exhibiting systematic dependencies on V/III ratio. The DLTS spectra are dominated by traps at EC − 0.14 eV and EC − 0.67 eV, whose concentrations decreased monotonically with increasing V/III ratio and decreasing oxygen impurity concentration, and by a trap at EC − 0.21 eV that revealed no dependence of its concentration on growth conditions, suggestive of different physical origins. Higher concentrations of deeper trap states detected by DLOS with activation energies of EC − 2.65 eV and EC − 3.31 eV in each sample did not display measureable sensitivity to the intentionally varied V/III ratio, necessitating further study on reducing these deep traps through growth optimization for maximizing material quality of NH3-MBE grown m-plane GaN.