气相传输平衡法在(11-20)面蓝宝石上制备γ铝酸锂膜

为了寻找可能替代蓝宝石作为氮化镓外延的新型衬底,通过48 h的气相传输平衡,分别在1000℃、1030℃、1050℃、1070℃和1100℃制备了一层单相多晶的γ铝酸锂膜。X射线衍射和扫描电镜分别用于表征膜的物相、取向和表面形貌。结果显示,γ铝酸锂择优取向的好坏取决于气相平衡传输温度,在1050℃制备的γ铝酸锂具有高度的100]择优取向;在γ铝酸锂(001)面上的双轴拉应力可能有助于100]择优取向的形成;γ铝酸锂晶粒表面裂纹的方向一致性与其择优取向紧密相关。上述结果表明在合适的工艺条件下,气相传输平衡法制备的γ铝酸锂/蓝宝石可能成为一种很有前景且适合(1-100)面氮化镓生长的复合衬底。

Preparation of γ-LiAlO2 Layer on (11-20)Sapphire by Vapor Transport Equilibration

In order to find a new substrate which can probably substitute the sapphire for GaN epitaxy, a single phase and polycrystalline γ-LiAlO2 layer has been prepared by vapor transport equilibration (VTE) for 48 hours at 1000 ℃, 1030 ℃, 1050 ℃, 1070 ℃ and 1100 ℃, respectively. X-ray diffraction (XRD) and scanning electronic microscope (SEM) have been used to characterize the phase, orientation and surface morphology. The results show that the preferred orientation of γ-LiAlO2 layer depends on temperature. The γ-LiAlO2 layer prepared at 1050 ℃ has a highly preferred 100] orientation. A biaxial tensile stress existing in (001) γ-LiAlO2 may contribute to the form of the preferred 100] orientation. The directional coherence of stripes on the surface of γ-LiAlO2 grains closely corresponds to the preferred orientation of γ-LiAlO2 layer. The above results indicate that the γ-LiAlO2/α-Al2O3 prepared by vapor transport equilibration under appropriate conditions probably provides a promising compound substrate which adapts to grow (1-100) GaN film.