Self‐organized growth of cubic InN dot arrays on cubic GaN using MgO (001) vicinal substrates

Abstract

Cubic zincblende InN (c‐InN) nanoscale dot arrays are grown on cubic GaN (c‐GaN) by RF‐molecular beam epitaxy using MgO (001) vicinal substrates oriented 3.5° toward [110]. The obtained dot arrays have longer ordering length compared with those grown using conventional on‐axis (just) substrates. The c‐GaN underlayer grown on the vicinal substrate exhibits a single‐domain crystalline structure, while that grown on the just substrate is a mixture of two orthogonal crystalline domains. The change in the c‐GaN domain structure leads to the enlarged domain size and lower density of domain boundaries on the c‐GaN (001) surface in [1–10]. The longer ordering length of the c‐InN dot on the vicinal substrates is reflected by the decrease in the c‐GaN domain boundary that disrupts the lateral ordering of the dot arrays. Atomic force microscope image of c‐InN dots grown on a single‐domain c‐GaN. The sample was fabricated using a MgO (001) vicinal substrate.

Growth temperature dependence of cubic GaN step structures and cubic InN dot arrays grown on MgO (001) vicinal substrates

“…The controllable ranges of these structural parameters are much extended compared with those in our previous study, which are 59-98 nm in lateral size, 9.3-11.4 nm in height, and 8.0 × 10 9 -1.6 × 10 10 cm −2 in density. 15) The c-InN dots grown at 530 °C showed an elongated shape or wire-like nanostructures of which the long axis parallel to [110] c-GaN . Positional dot alignment along the multistep edges on the underlayer was observed under some conditions.…”

“…On the other hand, c-GaN layers grown on MgO (001) 3.5°off vicinal substrates have a single-domain crystalline structure in which [110] c-GaN is parallel to [110] MgO rather than forming a mixture of the two orthogonal domains, as we previously reported. 15) Therefore, the higher uniformity of the lateral orientation of the elongated c-InN dots on the 3.5°off surface is considered to originate from the crystallographic domain singularity of the c-GaN underlayer. In contrast, the comparable densities of the elongated c-InN dots with the long axis along the [110] MgO and those along [1][2][3][4][5][6][7][8][9][10] .…”

“…[10][11][12] We previously reported the self-assembled growth of InN dots in both cubic zincblende phase and hexagonal wurtzite phase. [13][14][15][16] These studies revealed that lateral dot array structures were formed by the preferential growth of InN dots along atomic step or multistep edges on the surface of the GaN underlayer. Therefore, it is also important to control the GaN surface step structures such as step direction, density, period and periodicity to obtain a desired dot array structure.…”

“…In our previous work on the growth of cubic (c-) InN dots using MgO (001) substrates, we found that utilizing vicinal substrates was particularly effective to enhance the uniformity of the surface step direction on the c-GaN underlayer and it resulted in extended ordering length of laterally aligned c-InN dots. 15) Thus, we assume that c-GaN grown on vicinal substrates is a prospective candidate as a template for fabricating highly-ordered c-InN dot arrays. From this point of view, in this study, we investigated the changes in the step structures on the surface of c-GaN with respect to the growth conditions such as the substrate off-cut angle and the growth temperature.…”

Growth of High Mobility InN Film on Ga‐Polar GaN Substrate by Molecular Beam Epitaxy for Optoelectronic Device Applications

“…[11,12] The growth of high quality InN is challenging due to impurity incorporation, low dissociation temperature, narrow growth window and lack of suitable substrate. [13][14][15][16][17][18][19][20] There are several methods to deposit InN epitaxial layer such as metal-organic chemical vapor deposition, pulsed vapor deposition, sputtering, hydride vapor phase epitaxy and molecular beam epitaxy (MBE). [19,[21][22][23][24][25][26][27][28] Among them, MBE is the most sophisticated growth technique, which can grow high quality InN structure under precise control.…”