The Research Of GaN Epitaxial Growth On Si Substrate

Gallium nitride (GaN) became the third generation of semiconductors because ofit’s advantages of stability of chemical properties,substain of high temperature,largeband gap,high-frequency and high power, however, due to the lack of homogeneity ofGaN epitaxial materials, we use heteoepitaxial generally. Commercial GaN epitaxyare generally on sappire substrates. Compared to the sapphire substrate, because of theadvantages of large size, low cost, high thermal conductivity, integrated with Si-basedmicroelectonic device, etc. the Si substrate turns into the ideally material of GaNepitaxial rapidly. However there are many technical difficulties of growing GaNepitaxial layer on Si substrate compared with the growth on sapphire substrate.FirstlyGaN will react with the Si substrate intensely and rust the epitaxial layer. Secondly,due to the large lattice mismatch and thermal mismatch between the GaN epitaxiallayer and Si substrate, it will cause the problems of dislocations and cracks. For theseproblems, this article wil discuss the growth of GaN on Si substrate by MOCVD, themain contents are as follows:(1) We research the time of bedding Al on Si substrate and the growth process of AlN.The results shows that the time of bedding Al can not only inhibite the nitride ofsubstrate but also influence the growth of AlN follow-up.The change of theparameter of pulse methods of growing high temperature AlN will influence thequality of the GaN epitaxial layer.(2) The optimization of high temperature AlN buffer layer. The buffer layer couldprevent the dislocaions elongation effectively, introduce strain stress in GaNepitaxial layer and will release even remove the crack. We conclude that we couldget high quality GaN epitaxial layer when the growth temperature of hightemperature AlN buffer layer is at1060~1070℃and the thickness of buffer layer isat160nm.(3) We get the conclusion by introducing double buffer layersHT-AlN/LT-AlN/HT-AlN, that the low temperature interlayer play an importmantpart of releasing cracks, but it will influence the quality of GaN layer negatively.(4) On the basis of double buffer layers HT-AlN/LT-AlN/HT-AlN, we recommend theinterlayer of AlxGa1-xN. It has a special significance for reducing cracks in GaNepitaxial layer and improving the crystal quality of GaN layer.It’s also animportant role for improving the surface of GaN epitaxial layer.So it’s an important craft which we need to research rigorously. Throuht experiments, weconclude the best result of the number and the thinkness of the layers.