Hydride Vapor Phase Epitaxy Growth of Semipolar (1013)GaN on Patterned m-Plane Sapphire

Abstract

We have investigated the hydride vapor-phase epitaxy growth of ͑101 ¯3 ¯͒-oriented GaN thick films on patterned sapphire substrates ͑PSSs͒ ͑101 ¯0͒. From characterization by atomic force microscopy, scanning electron microscopy, double-crystal X-ray diffraction, and photoluminescence ͑PL͒, it is determined that the crystalline and optical qualities of ͑101 ¯3 ¯͒ GaN epilayers grown on the cylindrical PSS are better than those on the flat sapphire. However, two main crystalline orientations ͑101 ¯3 ¯͒ and ͑112 ¯2͒ dominate the GaN epilayers grown on the pyramidal PSS, demonstrating poor quality. After etching in the mixed acids, these ͑101 ¯3 ¯͒ GaN films are dotted with oblique pyramids, concurrently lining along the ͗303 ¯2 ¯͘ direction, indicative of a typical N-polarity characteristic. Defect-related optical transitions of the ͑101 ¯3 ¯͒ GaN epilayers are identified and detailedly discussed in virtue of the temperature-dependent PL. In particular, an anomalous blueshift-redshift transition appears with an increase in temperature for the broad blue luminescence due to the thermal activation of the shallow level.

Defect-related emission characteristics of nonpolar m-plane GaN revealed by selective etching

“…In our previous results, the epitaxial GaN layers directly grown on m-plane sapphire demonstrate (1 0 1 3 ) semipolar orientation [16,17]. The thickness of semipolar epilayer may be lessened about 8-12 mm in hot acids for 5 min.…”

Improvement of (11-22) GaN on m-Plane Sapphire With CrN Interlayer by Using Molecular Beam Epitaxy

“…However, the PL intensity of semipolar GaN grown with inserted CrN was ten times larger than GaN grown without the inserted CrN at room temperatures, which probably originated from the ameliorated crystalline quality of GaN, owing to the rough surface of deteriorated crystalline quality scattered part of PL signal. 19 In contrast, the BSF-related emission in the PL spectra of the semi-polar GaN grown with the inserted CrN was relatively lower and the NBE peak at the lower temperature was due to the BSF reduced by the improved crystalline quality. 5b, the BSF-related emission decreased faster than NBE as the temperature increased.…”

“…The 3.472 eV emission band, according to previous results of non-polar GaN, may correspond with the common GaN near bandedge emission (NBE). 19, which found that BSF-related emissions may arise from bundles of BSF. 17 Compared to GaN grown without the inserted CrN, a slight red-shift around 2 meV in the NBE peak energy with the inserted CrN was observed.…”

“…6a and 6b. 19 On the other hand, the DAP-related peak at 3.291 eV is rapidly quenched and it is difficult to identify at 60 and 120 K for semi-polar GaN grown with and without the inserted CrN, respectively. The best fit was obtained with a ¼ 6.7 Â 10 À4 and 6.7 Â 10 À4 eV/K and b ¼ 820 and 930 K for semi-polar GaN grown with and without the inserted CrN, respectively.…”

Defect reduction in semipolar {101̄3̄} GaN grown on m-sapphire via two-step nanoepitaxial lateral overgrowth

“…A detailed investigation has been reported in ref. 24. It is reported that the dislocations in the semipolar GaN epilayers include Frank-Shockley PDs with Burgers vector b = 1/6 <202 ¯3> (90%), Shockley PDs with b = 1/3 <101 ¯0> (8%) and perfect dislocations of a-type with b = 1/3 <112 ¯0> (2%).…”