(1■02)r面蓝宝石生长的(11■0)a面氮化镓研究

Study of (11■0) non polar a-plane GaN on the (1■02) r-plane sapphire

自发极化和压电极化是氮化镓制作光电器件没有解决的问题,对非极性GaN材料的研究解决了极化现象.采用低温AlN作为缓冲层,在(1■02)r面蓝宝石和(0001)c面蓝宝石上分别生长了(11■0)非极性a面和(0001)极性c面GaN,用原子力显微镜和高分辨X射线衍射、光致发光谱比较了生长在r面蓝宝石上的a面GaN和c面蓝宝石上的c面GaN,a面GaN材料质量和c面GaN相差较大,在a面GaN上发现了三角坑的表面形貌,这和传统的c面生长的极性GaN截然不同.对a面GaN的缺陷形成原因进行了讨论,并且确定了三角坑缺陷的晶向.

The spontaneous and piezoelectric polarizatio represent one of the unsolved problems in utilizing GaN for fabricating light-emitting devices. To solve the problem, non-polar GaN structures have been studied. Low-temperature AIN buffers are used for （1150） a-plane GaN growth on the （1^-102） r- plane sapphire. A combination of atomic force microscopy （AFM）, high resolution X-ray diffraction （XRD） and photoluminescence （PL） spectrum is used to characterize dislocation of the （11^-20） a-plane and （0001） c plane GaN epilayer. Compared with the typical hexagonal dislocation of c-plane GaN, this shows great difference with the conventional polar GaN, and the pit of the a-plane GaN epilayer is triangle, with the possible formation mechanisms of these faults discussed and the triangular pit directions also investigated.