2011, Vol.21, No.3

Journal of the Korean Crystal Growth and Crystal Technology 2023 KCI Impact Factor : 0.19

pISSN : 1225-1429 / eISSN : 2234-5078
https://journal.kci.go.kr/jkcgct

A stoichiometric mixture of evaporating materials for MgGa2Se4 single crystal thin films was prepared from horizontal electric furnace. The crystal structure of these compounds has a rhombohedral structure with lattice constants a0 =3.953 Å, c0 = 38.890 Å. To obtain the single crystal thin films, MgGa2Se4 mixed crystal was deposited on thoroughly etched semi-insulating GaAs(100) substrate by the Hot Wall Epitaxy (HWE) system. The source and substrate temperatures were 610oC and 400oC, respectively. The crystalline structure of the single crystal thin films was investigated by the double crystal X-ray rocking curve and X-ray diffraction ω-2θ scans. The carrier density and mobility of MgGa2Se4 single crystal thin films measured from Hall effect by van der Pauw method were 6.21 × 1018 cm−3 and 248 cm2/v·s at 293 K, respectively. The optical absorption of MgGa2Se4 single crystal thin films was investigated in the temperature range from 10 K to 293 K. The temperature dependence of the optical energy gap of the MgGa2Se4 obtained from the absorption spectra was well described by the Varshni’s equation, Eg(T) = Eg(0) − (αT2/T + β). The constants of Varshni’s equation had the values of Eg(0) = 2.34 eV, α = 8.80 × 10−4 eV/K and β = 251 K, respectively.

Critical angle of quartz (R.I.≒1.553) and diamond (R.I. = 2.417) are 40.09oand 24.26othat calculated by sinθ = r2/r1 (r = refractive index, r1 > r2). Brilliance of quartz and diamond are 20.33 % and 55.07 %. The brilliance data are result of study on the incident light internal round brilliant cut quartz and diamond by the critical angle. Cause of bow-tie phenomenon can be studied by application of critical angle theory and light path inside fancy shape brilliant cut. When refractormetry with typical gem refractometer, critical angle of quartz and corundum are 59.1oand 77.9o.

In this paper, we propose a new method for the fabrication of GaN microstructures formed only on the vertex of GaN pyramid by using of metal catalysts. GaN pyramidal structures were selectively grown on 3 μm SiO2 dot patterns followed by thin film deposition of Au and Cr only on the vertex area of the GaN pyramids with precisely controlled photolithography. After the metal deposition, the samples were loaded in the MOVPE reactor for the growth of GaN microstructures for 10 minutes. Temperature for the growth of the GaN microstructures was changed from 650oC to 750oC. Rod type GaN microstructures were grown in the direction of vertical to the six {1-101} facets and the shape of the GaN microstructures was changed depend on the type of metal.