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1 Journal of Achievements in Materials and Manufacturing Engineering

1 2007

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Crystal quality and electrical properties of p-type GaN thin film on Si(111) substrate by metal-organic chemical vapour deposition MOCVD

Wu G. M., Hsieh T. H.

Journal of Achievements in Materials and Manufacturing Engineering

2007

Vol. 24, nr 1

193-197

Purpose: In this paper, p-GaN samples have been grown on silicon substrates under various processing conditions. The effects of growth temperature and thermal annealing on the crystal quality and strain were carefully investigated. The electrical properties such as hole concentration and mobility would be discussed. Design/methodology/approach: GaN-based III—V semiconductors have become promising materials for short-wavelength optoelectronic devices because of their large and direct band gap energies. In this paper, p-GaN has been grown by metal-organic chemical vapor deposition (MOCVD) at 900 , 950, 1000, and 1050 degrees centigrade with low temperature LT-deposited AlN/AlGaN buffer layer. Findings: The mobility was achieved at 150 square cm/Vs and the hole concentration was 8x10 to the 17 - cubic cm. SIMS and XRD were used to measure and explain the relationships between hole concentration and the growth temperature. When the growth temperature was increased to 1000 degrees centigrade, the hole concentration was increased by ten times. According to the experimental results, the optimal growth temperature was 1000 degrees centigrade. After the thermal annealing process at temperature 850 degrees centigrade for 2 minutes, the FWHM of p-GaN was lowered to 617 arcsec. The effects of growth temperature were explained in the two temperature regions. From 900 to 1000 degrees centigrade, the incorporation rate of Mg was slightly increased and the strain decreased with the growth temperature. Mg would provide holes and the lower strain would result in better crystal quality. The crystal quality and Mg concentration effects on hole concentration below 1000 degrees centigrade was thus beneficiary. On the other hand, when the growth temperature was further increased, the strain and FWHM increased while hole concentration decreased at 1050 degrees centigrade. At this high temperature, Si might become donor in GaN. Research limitations/implications: It was suggested that the hole concentration reduced at 1050 degrees centigrade due to the Si diffusion and the strain caused by Mg dopant. According to the experimental data, the optimal growth temperature was 1000 degrees centigrade. After the annealing process, the FWHM of p-GaN was lowered to 611 arcsec. Originality/value: Determination of crystal quality and electrical properties of p-type GaN thin film on Si(111) substrate by metal-organic chemical vapor deposition MOCVD.