Growth of non-polar a-plane AlN on r-plane sapphire

Abstract

Growth of non-polar AlN is crucial to the realization of polarization-free light-emitting diodes in deep UV range. The aim of this study was to investigate the growth condition for obtaining a flat a-plane AlN on r-plane sapphire. A thin AlN layer grown at lower temperature played an important role in protecting the sapphire surface. Both high temperature and low V/III ratio were necessary in terms of enhanced adatom diffusion, leading to the formation of a flat AlN buffer.

Non‐Polar a‐Plane AlN Growth on Nitrided r‐Plane Sapphire by Ga–Al Liquid‐Phase Epitaxy

“…The EADM value was decreased to 0.22% by tilting the AlN plane by 4 , as shown in Figure 1(b). In the r-plane sapphire substrate, the two symmetric opposite a-axis directions [11][12][13][14][15][16][17][18][19][20] and [-1-120] exist. Therefore, tilted double domain AlN formed on the nitrided r-plane www.advancedsciencenews.com www.pss-b.com sapphire, as observed in Figure 4.…”

“…Figure 1(c) shows the definition of the off-cut angle used in this study. AlN and GaN growth on an r-plane sapphire substrate with an off-cut direction toward [0001] has been previously reported [11][12][13][14]27] ; however, AlN growth on an r-plane sapphire substrate with an off-cut direction toward [11][12][13][14][15][16][17][18][19][20] as shown in Figure 1(c), has not been previously reported. The experimental details for thermal nitridation have been described in previous papers.…”

“…The a-axis of the single domain AlN was tilted by 5 from the normal direction of the off-cut substrate, as illustrated in Figure 1 Figure 8 shows the atomic arrangement relationship between a-plane AlN and r-plane sapphire. Figure 8 indicates that a large lattice misfit of 13.0% exists along the direction of AlN[1-100]jj sapphire [11][12][13][14][15][16][17][18][19][20]. The extended atomic distance mismatch (EADM) is defined as [28]…”

“…Therefore, a ‐plane AlN growth on r ‐plane sapphire is an important technology to realize high‐efficiency DUV‐LEDs. Some groups have grown a ‐plane AlN layers on r ‐plane sapphire substrates by metal–organic chemical vapor deposition and HVPE …”

“…Therefore, a-plane AlN growth on r-plane sapphire is an important technology to realize high-efficiency DUV-LEDs. Some groups have grown a-plane AlN layers on r-plane sapphire substrates by metal-organic chemical vapor deposition [11][12][13] and HVPE. [14] Our group has developed several techniques to fabricate AlN layers on sapphire substrates.…”