Low-Angle-Incidence Microchannel Epitaxy of $a$-Plane GaN Grown by Ammonia-Based Metal–Organic Molecular Beam Epitaxy

Low-pressure microplasma treatment was performed to clean a substrate surface prior to the selective growth of GaN by chemical beam epitaxy. To investigate the cleaning mechanism, the process pressure and process time were systematically varied. The plasma distribution was also studied using a special sheet, whose color changes following the irradiation of plasma species. Consequently, it was found that the range of microplasma irradiation increased with decreasing process pressure, and simultaneously, the morphology of selective growth was improved. Secondary ion mass spectrometry measurements show that the oxygen concentration at the growth interface was reduced from 9.7 × 1014 to 2.6 × 1013 atoms/cm2 by the microplasma treatment. Otherwise, the surface oxides resulted in the growth of a rough surface with the suppression of the layer-by-layer growth.

Section: Methodsmentioning

confidence: 99%

Low-pressure N₂ microplasma treatment for substrate surface cleaning prior to GaN selective growth

Kusakabe

Sugiyama

Takenaka

et al. 2018

“…These conditions were optimal for obtaining a flat and wide lateral growth. 8) The morphology of the samples was studied using scanning electron microscopy (SEM).…”

Section: Experimental Methodsmentioning

confidence: 99%

“…7) The temperature and [NH 3 ]/[TMG] (TMG: trimethylgallium) flow rate dependences of a-plane GaN LAIMCE have been studied to optimize the growth conditions for obtaining a wide lateral overgrowth. 8,9) The crystal direction of the microchannel is another important factor for controlling lateral growth because it largely affects facet formation on the sides. Therefore, in the present study, the effects of the direction of precursor supply were investigated.…”

Section: Introductionmentioning

confidence: 99%

Effect of Supply Direction of Precursors on a-Plane GaN Low Angle Incidence Microchannel Epitaxy by Ammonia-Based Metal–Organic Molecular Beam Epitaxy

Uchiyama¹,

Lin²,

Suzuki³

et al. 2013

Self Cite

The effects of varying the supply direction of precursors on a-plane GaN low angle incidence microchannel epitaxy by ammonia-based metal–organic molecular beam epitaxy were studied. Lateral growth was found to be wider when precursors were supplied from the [0001] direction than from the [0001̄] direction. The (0001̄) face formed on the supply side suppressing lateral growth when the precursors were supplied from the [0001̄] direction, while lateral growth was enlarged by the intersurface diffusion of adatoms from the side to the top when supplied from the [0001] direction. A smaller cross-section of lateral growth was experimentally observed when the (0001̄) face appeared on the supply side, which suggests that the chemical character of the side also affects lateral growth. The offset angle of the opening is another important factor for determining the lateral growth, which largely affects the formation of facets on the sides and, consequently, the grown shape.

“…As a result, a dislocation-free area of a-plane GaN lateral growth, whose width was as large as 2 µm, was obtained by LAIMCE with MOMBE. 21) Moreover, a uniform a-plane GaN LAIMCE was achieved by the coalescence of the neighbouring layers. 22) The decrease in the width of the microchannel was attempted for the reduction in the number of dislocations in the grown layer because dislocations remain only in the areas over the microchannel.…”

Section: Introductionmentioning

confidence: 99%

Effect of N₂ microplasma treatment on initial growth of GaN by metal–organic molecular beam epitaxy

Suzuki

Kusakabe

Uchiyama

et al. 2016

Self Cite

N2 atmospheric microplasma was applied to improve the yields and reproducibility of the initial growth of GaN by metal–organic molecular beam epitaxy (MOMBE). The plasma treatment was found to be effective in cleaning the surface, and excellent flat growth was achieved even in the early stage of the growth. The effect of the air exposure after plasma treatment was also studied, and the yield of the growth was found to be largely decreased by the air exposure even after the treatment. Therefore, the oxidation of the substrate is one of main causes of the poor initial growth and the installation of the microplasma equipment in the MBE loading chamber is useful for suppressing the oxidation after the treatment. Atomic force microscopy (AFM) measurement shows that the microplasma treatment is also effective for undoing the surface double steps through etching, which is helpful for a very smooth layer-by-layer growth in the early stage of growth.