Effects of Initial Thermal Cleaning Treatment of a Sapphire Substrate Surface on the GaN Epilayer

Abstract

We investigated the effects of the in situ thermal cleaning treatment of a (0001) sapphire substrate surface in hydrogen ambient on the structural, optical, and electrical properties of epitaxial GaN films grown by metalorganic chemical vapor deposition (MOCVD). Hall effect, X-ray diffraction (XRD), and photoluminescence measurements of GaN films grown at 1040 • C clearly indicate that the film quality is strongly affected by the thermal cleaning treatment of the substrate surface. GaN films under the optimized thermal cleaning treatment at 1070 • C for 10 min showed minimum full-widths at half maximum (FWHMs) of 273 arcsec and 728 arcsec for (002) and (102) XRD peaks, respectively. In addition, the FWHM of the band-edge emission peak was as narrow as 28.3 meV, and the intensity ratio between the band edge emission and the yellow band emission was as high as 100 at room temperature. It was also found that the roughness of sapphire surface was reduced after the thermal treatment.

Optimization of nucleation and buffer layer growth for improved GaN quality

“…Oxygen doping was done with a mixture of 0.3% oxygen in nitrogen. Before deposition, the substrates went through in situ annealing [25] at 1200 1C for 10 min in a hydrogen atmosphere. A reduced reactor pressure between 70 and 200 mbar and the standard precursors trimethyl-aluminum (TMAl), trimethyl-gallium (TMGa) and high-purity ammonia were used to deposit the NL and the nominally undoped GaN layer, respectively.…”

III–Nitride Epitaxy on Atomically Controlled Surface of Sapphire Substrate with Slight Misorientation

“…It is reported that the surface condition of sapphire substrate affects the quality of grown III-nitride films. [28][29][30] If the surface is an unfavorable condition with remained scratches etc., the surface roughness of such surface becomes larger than that of ideal model. To obtain the perfect atomic relationship between sapphire and III-nitride in vertical direction, atomically well-controlled surface of sapphire substrate in relation to misorientation and ideally minimized surface roughness is necessary.…”

Fractal analysis of surface topography in ground monocrystal sapphire

“…However, all these optoelectronic devices require sapphire with high machining quality and defect-free surfaces. For example, as a substrate material for laser diodes, the machining defects present at the sapphire surface can cause laser damage and drastically limit the optics lifetime [3,4]. So the optical performance is highly dependent on the surface quality and the degree of surface/subsurface damage.…”