Characteristic comparison between GaN layer grown on c-plane cone shape patterned sapphire substrate and planar c-plane sapphire substrate by HVPE
Abstract
GaN layers were grown on planar c-plane sapphire (Sample A) and c-plane cone-shape patterned sapphire substrate (PSS) (Sample B) with two growth steps by a hydride vapor phase epitaxy (HVPE).
While the growth rate of GaN layers on planar c-plane sapphire was higher than that on PSS, the full width at half maximum (FWHM) values of sample B were lower than the FWHM values of sample A. The FWHM values of rocking curve for GaN (0 0 2) and (1 0 2) of sample B were 361 and 354 arcsec, respectively. According to the measurement of photoluminescence (PL) at room temperature, the quality of the sample B was better than the sample A. The SEM cross sectional image of sample B exhibited voids in the top region of the pattern. The density of threading dislocations (TDs) for the sample A and B was calculated to be 8 × 108 cm-2 and 4 × 108 cm-2, respectively. It is suggested that the structural defects for the sample B were merged in the top region of the pattern during the 1st growth step and TDs were reduced or suppressed during the 2nd growth step in top region of the pattern. The GaN layer grown on PSS (Sample B) exhibited better optical properties and crystal quality than the GaN layer grown on planar c-plane sapphire (Sample A).- Publication:
-
Journal of Crystal Growth
- Pub Date:
- July 2018
- DOI:
- 10.1016/j.jcrysgro.2018.04.022
- Bibcode:
- 2018JCrGr.493....8L
- Keywords:
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- GaN;
- Patterned sapphire substrate (PSS);
- Photoluminescence (PL);
- CL mapping;
- Red shift;
- Growth mechanism