温梯法白宝石晶体的表面形貌研究

Study on Surface Morphology of Sapphire Crystal Grown byTemperature Gradient Technique(TGT)

本文采用导向温梯法 (TGT)生长 [0 0 0 1 ]方向的白宝石晶体 ,利用气相传输平衡 (VTE)技术对晶体表面进行处理 ,发现双面抛光的C面白宝石晶片高温下与富锂 (Li2 O蒸气 )气氛发生反应 ,表面生成一层γ LiAlO2 ,随着VTE反应温度从 75 0℃下降到 730℃ ,γ LiAlO2 晶核的颗粒也随着减小 ,在 730℃时已在 1 μm以下 ,经稀盐酸 (HCl)腐蚀后形成多孔的表面 。

High quality sapphire crystal oriented along [0001] was grown by the temperature gradient technique (TGT) and subsequently was fabricated into well double-polished (0001) sapphire wafers. These (0001) sapphire wafers were processed by vapor transport equilibration (VTE) technique under high temperature and in Li-rich ambient. As a result, a single-phase γ-LiAlO2 layer was formed on wafer surface. The sizes of γ-LiAlO2 grains decreased with the drop of VTE process temperature from 750°C to 730°Ct. In the case of 730°C, the sizes of γ-LiAlO2 grains were already under 1 μ. Above-mentioned sapphire wafers with γ-LiAlO2 grains were then subjected to dilute muriatic acid (HCl), so γ-LiAlO2 grains were etched and removed, thus brought a froth porous surface. It is promising to fabricate porous substrates by VTE technique for GaN epitaxial growth.