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人们已提出用BAlGaN四元系材料制备紫外光谱区的光发射器件。GaN和AlN二元系是这种四元材料在器件应用中的基础材料。 6H SiC衬底在氮化物生长中因其晶格失配小是一大优势 ,而且SiC衬底的热膨胀系数也和AlN的很接近。然而 ,对于AlN外延层来说 ,需要控制其中的残余应力 ,因为在SiC衬底上直接生长的AlN外延层中存在着因晶格失配所产生的压缩应力。另一方面 ,在SiC衬底上直接生长的GaN外延层中存在着拉伸应力。这种拉伸应力起源于GaN比衬底有着更大的热膨胀系数。本文讨论了在 6H SiC衬底上生长的氮化物外延层中残余应力的类型、数量及控制。为此目的 ,提出了在 6H SiC衬底上 ,无论是生长AlN ,还是生长GaN ,都可以采用 (GaN/AlN)多层缓冲层的办法 ,作为控制残余应力的有效方法。我们还讨论了AlN和GaN外延层的结晶质量和残余应力间的关系。
It has been proposed to use the BAlGaN quaternary material to prepare a light-emitting device in the ultraviolet region. GaN and AlN binary systems are the basic materials for this quaternary material in device applications. 6H SiC substrate is a major advantage of lattice mismatch in the growth of nitride, and the thermal expansion coefficient of SiC substrate is very close to that of AlN. However, for the AlN epitaxial layer, the residual stress needs to be controlled because of the compressive stress caused by lattice mismatch in the AlN epitaxial layer directly grown on the SiC substrate. On the other hand, there is tensile stress in the GaN epitaxial layer grown directly on the SiC substrate. This tensile stress originates from GaN having a larger coefficient of thermal expansion than the substrate. This article discusses the type, amount and control of residual stress in nitride epitaxial layers grown on 6H SiC substrates. To this end, it is proposed that a (GaN / AlN) multilayer buffer layer can be used as an effective method for controlling residual stress on a 6H SiC substrate whether grown AlN or grown GaN. We also discuss the relationship between the crystalline quality and residual stress of AlN and GaN epitaxial layers.