Polar Dependence of Threading Dislocation Density in GaN Films Grown by Metal-Organic Chemical Vapor Deposition

We investigate the threading dislocation(TD) density in N-polar and Ga-polar GaN films grown on sapphire substrates by metal-organic chemical vapor deposition.X-ray diffraction results reveal that the proportion of screw type TDs in N-polar GaN is much larger and the proportion of edge type TDs is much smaller than that in Ga-polar.Transmission electron microscope results show that the interface between the AlN nucleation layer and the GaN layer in N-polar films is smoother than that in Ga-polar films,which suggests different growth modes of GaN.This observation explains the encountered difference in screw and edge TD density.A model is proposed to explain this phenomenon.     

优质大尺寸Nd：YAG晶体生长技术的研究

本文研究了Ｎｄ：ＹＡＧ晶体由于小面的生长而产生核心与侧心的机理。讨论了熔体生长Ｎｄ：ＹＡＧ晶体的固液界面形状和温度梯度及小面生长的内在联系；探讨了消除侧心、减小核心的技术途径；并生长出无侧心、小核心Ｎｄ：ＹＡＧ晶体。     

Semipolar(1122) and polar(0001) InGaN grown on sapphire substrate by using pulsed metal organic chemical vapor deposition

High indium semipolar(1122) and polar(0001) In Ga N layers each with a thickness of about 100 nm are realized simultaneously on sapphire substrates by pulsed metal organic chemical vapor deposition(MOCVD). The morphology evolution, structural and optical characteristics are also studied. The indium content in the layer of the surface(1122)is larger than that of the surface(0001), which is confirmed by reciprocal space map, photoluminescence spectrum and secondary ion mass spectrometer. Additionally, the(0001) surface with island-like morphology shows inhomogeneous indium incorporation, while the(1122) surface with a spiral-like morphology shows a better homogeneous In composition.This feature is also demonstrated by the monochromatic cathodoluminescence map.