Influence of micro-patterning of the growth template on defect reduction and optical properties of non-polar (112ˉ0) GaN

Abstract

We investigate the influence of different types of template micro-patterning on defect reduction and optical properties of non-polar GaN using detailed luminescence studies. Non-polar ( 11 2 ˉ 0 ) (or a-plane) GaN exhibits a range of different extended defects compared with its more commonly used c-plane counterpart. In order to reduce the number of defects and investigate their impact on luminescence uniformity, non-polar GaN was overgrown on four different GaN microstructures. The micro-patterned structures consist of a regular microrod array; a microrod array where the −c-side of the microrods has been etched to suppress defect generation; etched periodic stripes and finally a subsequent combination of etched stripes and etched microrods (double overgrowth). Overall the presence of extended defects, namely threading dislocations and stacking faults (SFs) is greatly reduced for the two samples containing stripes compared with the two microrod samples. This is evidenced by more uniform emission and reduction in dark regions of non-radiative recombination in room temperature cathodoluminescence imaging as well as a reduction of the SF emission line in low temperature photoluminescence. The observed energy shifts of the GaN near band edge emission are related to anisotropic strain relaxation occurring during the overgrowth on these microstructures. A combination of stripes and microrods is a promising approach for defect reduction and emission uniformity in non-polar GaN for applications in light-emitting devices as well as power electronics.

Defect characterization of {101¯3} GaN by electron microscopy

“…Most room temperature CL maps show a strongly reduced intensity at the location of BSFs, strongly indicating the presence of non-radiative recombination pathways (i.e., via point defects) at or close to BSFs. [68][69][70] The lack of such contrast in our study might tentatively be explained by a lower incorporation rate of point defects in (10 13). The monochromatic luminescence intensity map at 3.28 eV [Fig.…”

Cathodoluminescence studies of the optical properties of a zincblende InGaN/GaN single quantum well

“…In contrast, at room temperature these SFs in wz-GaN have reduced intensity [42]. This has been attributed to several factors in the literature, but the most common suggestion is the presence of point defects and dislocations at or around a SF that led to non-radiative recombination pathways [20,43,44]. As the carriers need little energy to escape the QW formed by the SF, and at room temperature thermal energy is available, carrier can diffuse to these low energy defect sites thereby leading to non-radiative recombination.…”

Comparative investigation of semipolar (11–22) GaN grown on patterned (113) Si with different V/III ratios via MOCVD

“…In addition, the AlN layer before GaN can not only reduce the Ga-melting back, but also can effectively improve the quality of GaN crystals [25]. The quality of (11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22) GaN grown by this method still depends sensitively on many parameters, such as trench width [26], growth temperature [27], V/III ratios, etc [28][29][30]. For example, semipolar (11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22) GaN can be grown on (113) Si in the V/III ratio range of 470-1730 [24,28,29,31,32], but there is a significant difference in the quality of the GaN.…”