SiC衬底上外延GaN:Mg材料特性研究

Characterization of Mg-doped GaN

利用扫描电子显微镜、拉曼散射光谱和光致发光谱对在SiC衬底上采用MOCVD异质外延的GaN :Mg薄膜特性进行研究发现 :除了一部分Mg原子替代Ga原子呈现受主性外 ,大部分Mg原子以间隙原子状态 (Mgi)存在 ,并且在缺陷或者位错处大量聚集引起薄膜张力应力减小 ,薄膜在降温过程中由于应力不均匀会在部分区域内出现大量的裂纹 ;Mg的掺杂会加剧GaN无序化程度 ,致使薄膜质量变差 ;而室温下的PL谱测量表明蓝带发光由DAP(深施主—浅受主 )复合引起 ,其中D为MgGaVN ,A为MgGa.

The properties of GaN∶Mg films grown by MOCVD on SiC substrate were studied using SEM, Raman scattering and photoluminescence spectra. The results indicate that some Mg atoms substitute Ga to become acceptors, while most of them exist as Mg interstitials(Mg i) and aggregate at defects and dislocations to reduce the tensile stress, hence a great deal of cracks were introduced during decreasing temperature process for inhomogeneous strain distribution. On the other hand, the incorporation of Mg aggravates disorder and debases the film quality. Finally, the room temperature photoluminescence measurements show the blue band attributed to DAP-type transitions from a deep donor(Mg GaV N) to a shallow acceptor(Mg Ga).