No abstract

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.

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.