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采用低温AlN成核层,在Si(111)衬底上,用金属有机化学气相沉积(MOCVD)法生长了GaN薄膜。采用高分辨X射线衍射(XRD)、椭圆偏振光谱仪和原子力显微镜(AFM)研究了AlN成核层的厚度对GaN外延层的影响。对AlN的测试表明,AlN的表面粗糙度(RMS)随着厚度增加而变大。对GaN的测试表明,所有GaN样品在垂直方向处于压应变状态,并且随AlN厚度增加而略有减弱。GaN的(0002)_ω扫描的峰值半宽(FWHM)随着AlN成核层厚度增加而略有升高,GaN(10-12)_ω扫描的FWHM随着厚度增加而有所下降。(10-12)_ω扫描的FWHM与GaN的刃型穿透位错密度相关,A1N成核层的厚度较大时会降低刃型穿透位错密度,并减弱c轴方向的压应变状态。
A low temperature AlN nucleation layer was used to grow a GaN film on a Si (111) substrate by metalorganic chemical vapor deposition (MOCVD). The influence of the thickness of AlN nucleation layer on the GaN epitaxial layer was investigated by high resolution X-ray diffraction (XRD), ellipsometer and atomic force microscopy (AFM). Testing of AlN shows that the surface roughness (RMS) of AlN becomes larger as the thickness increases. Tests on GaN show that all GaN samples are in a vertical, compressive state and weaken slightly as the AlN thickness increases. The FWHM of (0002) _ω scan of GaN increases slightly with the increase of the thickness of AlN nucleation layer. The FWHM of GaN (10-12) _ω scan decreases with the increase of thickness. The FWHM of (10-12) _ω scan is related to the edge penetrating dislocation density of GaN. When the thickness of AlN nucleation layer is larger, the edge threading dislocation density is reduced and the c-axis compressive strain is weakened.