Growth of cubic GaN on Si (100) Substrates
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0916-DD05-08
Growth of cubic GaN on Si (100) Substrates Suzuka Nishimura1, Shigeya Naritsuka2, and Kazutaka Terashima3 1 Materials Science and Technology, Shonan Institute of Technology, 1-1-25 Tshujidonishikaigan, Fujisawa, 2518511, Japan 2 Department of Materials Science and Engineering, Meijyo University, 1-501 Shiogamaguchi, Tenpakuku, Nagoya, Japan 3 Materials Science and Technology, Shonan Institute of Technology, 1-1-25 Tsujido-nishikaigan, Fujisawa, 2518511, Japan ABSTRACT We have focused to grow cubic GaN (c-GaN) on Si(100) substrates using boronmonophosphide(BP) buffer crystals. We have successfully grown BP crystals with electrically n-type and thickness deviation is within several % along 2inch wafer under undoped conditions on Si(100) substrates by MOVPE technique. The electrical conductivity of BP is less than 0.5mohm·cm. We have preliminary grown GaN by RF-MBE technique on BP/Si substrates. It has been found the cubic type GaN has been successfully grown on the substrates by measuring X-ray diffraction. The crystal quality and defect generation were observed by TEM. It has been found that there are much more dislocations than 109cm-2 generated at GaN/BP interface. INTRODUCTION The cubic type GaN has attracted many researchers attention due to its high carrier mobility and low piezo coefficient for use in high power optical devices. It has been reported to grow GaN on GaAs substrates [1, 2], but the lattice mismatch problem made the high concentrated defect in grown crystals. In addition, the chemical reaction between GaN and the substrates makes many problems. On the other hand, Si substrates are the most useful materials with large diameter and high crystal perfection. In this paper, the growth and evaluation of GaN crystals on the BP/Si(100) substrates have been investigated [3, 4]. We have preliminary grown GaN by RF-MBE technique on BP/Si. The GaN films grown by RF-MBE have been characterized in terms of SEM, TEM, X-ray diffraction and Photoluminescence measurement. EXPERIMENT c-GaN were grown on BP/Si(100) substrates by RF-MBE. BP/Si substrate size used was 15mm x 15mm. Thickness of BP layer on Si was about 1.2µm. It was attached on Mo block using In paste after organic cleaning. Then, it was introduced to growth chamber to grow GaN. The source materials used were Ga metal from K cell and N2 radical. BP/Si substrates were heated at 750˚C until streak patterns were clearly observed by RHEED. Then, GaN buffer layer was grown at low temperature 550˚C. After that, GaN layer was grown at 650˚C for 1 hour. Growth rate was varied from 0.2µm/h to 0.5µm/h depending on the Ga flow rate.
RESULTS AND DISCUSSION The GaN surface morphology is widely varied depending on V/III flux ratio even the temperature was fixed. The typical surfaces are shown in Fig.1a) Ga-rich conditions, and b) relatively flat face grown under low Ga flow. In the case of the crystal grown under Ga rich conditions, many Ga drop related crystals have been observed. It should be noted that each Ga drop related crystals have facets on it
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