双AlN插入层法在Si图形衬底上进行AlGaN/GaN HEMT的MOCVD生长

双AlN插入层方法被用来在Si（111）图形衬底上进行AlGaN/GaN高迁移率晶体管（HEMT）的金属有机物化学气相沉积（MOCVD）外延生长。Si图形衬底采用SiO2掩膜和湿法腐蚀（无掩膜）两种方法进行制备。高温生长双AlN插入层用来释放GaN外延层和Si衬底之间由于晶格失配和热失配而产生的张应力。AlGaN/GaN HEMT的生长特性被讨论和分析。在使用优化的双AlN插入层之前,可以在图形1-100]方向观察到比11-20]方向更多的由于应力而引起的裂纹。这是由于GaN在（1-100）面比（11-20）更稳定。建议在图形设计中,长边应沿着11-20]方向进行制备。拉曼测试显示在图形凹角处比凸角处有更大的拉曼频移,证明在图形凹角处有更大的张应力。

Growth Characteristics of AlGaN/GaN HEMTs on Patterned Si Substrates Using Double AlN interlayers by MOCVD Method

AlGaN/GaN high electron mobility transistors（HEMTs） were grown on un-patterned,patterned without mask,and patterned with mask Si（111） substrates by metal organic chemical vapor deposition（MOCVD）.The patterns on the Si substrates were fabricated by SiO2 masks and wet etching.Double AlN interlayers grown at high temperature were employed to relax the tensile stress induced by the large mismatches in the lattice constants and the thermal expansion coefficients.Growth characteristics of AlGaN/GaN HEMTs were discussed and analyzed.Before achieving optimized growth conditions,more cracking lines were observed on patterns along the orientation than along the orientation,resulted from more stable GaN（1-100） facets than GaN（11-20） facets.It is suggested that long patterns should be made along the orientation.Micro-Raman measurements showed that Raman shifts at the concave corners are bigger than those at the convex corners,indicating the presence of the larger stress at the concave corners.