Growth Mechanism of Nonpolar and Semipolar GaN Layers from Sapphire Sidewalls on Various Maskless Patterned Sapphire Substrates

Abstract

Nonpolar and semipolar GaN layers can be selectively grown from sapphire sidewalls of maskless patterned sapphire substrates (PSSs) by selective-area growth using a low-temperature (LT) GaN buffer layer. Various PSSs, such as a-PSS for m-GaN, r-PSS for (1122) GaN, c-PSS for m-GaN, and m-PSS for a-GaN, were prepared to investigate the growth mechanisms. It was revealed that the growth windows of various PSSs to achieve nonpolar or semipolar GaN grown from only the sapphire sidewall by changing the growth conditions are different. To determine the cause of selective-area growth in each PSS, GaN nucleation after annealing of the LT-GaN buffer layer was investigated by scanning electron microscopy, atomic force microscopy and X-ray diffraction analysis. Consequently, GaN was predominantly grown on a region with higher quality and better crystallo-ordered c-oriented GaN nucleation. When such nucleation of GaN occurs on the sapphire sidewall, it proceeds to grow selectively from the sapphire sidewall, and nonpolar or semipolar GaN can be obtained using maskless PSS.

Semipolar GaInN quantum well structures on large area substrates

“…1). Similar studies have been reported by Okada et al using a-, r-, m-, and c-oriented sapphire wafers [4,5]. Singularly oriented GaN growth from c-oriented side-facets was only obtained for r-and m-sapphire, whereas growth from the terraces or trench bottom areas or mixed growth was obtained in the other cases.…”

MOCVD of Nitrides

“…Figure 16.11 shows crosssectional views of the initial growth stage of GaN on each patterned Si substrate. The concept of using an etched side plane of the substrate for inclined c-plane GaN growth can also be applied to sapphire substrates [84,129,130]. Therefore, low-dislocation-density GaN can be obtained on the right of each GaN stripe.…”

Green light‐emitting diodes fabricated on semipolar (11–22) GaN on r‐plane patterned sapphire substrate

“…In principle, all the desired planes can be obtained using this technique. We have also studied other oriented GaN layers on many types of sapphire substrate as well as their growth mechanism [14][15][16][17]. This growth technique using patterned sapphire has been extensively used by several groups [18][19][20][21], and LED on an m-GaN layer using an a-PSS was demonstrated [22].…”

“…The growth temperature was 1050 8C. The growth conditions were constant by the end of the Figure 1 shows a cross-sectional scanning electron microscopy (SEM) image of the (11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22) GaN layer grown on the r-PSS. One salient characteristic of this sample is that air void structures were formed on the terrace region because of the facet growth mode.…”

“…3 Results and discussion 3.1 Photoluminescence To investigate the optical properties of the r-PSS, multi-quantum wells (MQWs) were evaluated by photoluminescence (PL) measurement. A (11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22) GaN layer on an m-plane sapphire substrate was prepared for comparison. The MQWs were fabricated on their substrates under the same growth conditions.…”