蓝宝石表面处理对氮化镓光学性质的影响

Effects of Surface Treatment for Sapphire on GaN Optical Propertities

采用化学方法腐蚀部分c面蓝宝石衬底,在腐蚀区域形成一定的图案,利用LP-MOCVD在经过表面处理的蓝宝石衬底上外延生长GaN薄膜.利用GaN薄膜光学透射谱,结合椭偏测量得到的折射率色散公式,计算得到GaN薄膜厚度,与椭偏光谱结果几乎一致;在经过表面处理的蓝宝石衬底上外延生长的GaN薄膜表现出更优异的光学质量和结晶质量,其透射谱具有更高的透射率和更大的调制深度,而且其光致发光谱中的黄光带几乎可以忽略.

Etch pits on sapphire substrate surface are formed after surface treating, GaN films have been grown by LP-MOCVD on the sapphire substrate,which a half of it is treated by chemical etch. Both the thickness and dispersion of the refractive index of GaN films are obtained by spectroscopic ellipsometry. With the dispersion of the refractive index,the transmission spectrum of GaN is studied and the thickness of GaN epilayer is calculated. The two values of the thickness obtained by these two different methods are in good agreement. The epilayer grown on the surface treated sapphire substrate exhibits superior optical properties and crystal properties, in which the yellow luminescence is nearly invisible in the photoluminescence spectrum, and the higher transmission ratio and the greater modulation depth can be shown in the transmission spectrum.