溅射制备非晶氮化镓薄膜的光学性能

采用直流磁控溅射方法在不同的氩气-氮气（Ar-N₂）气氛中制备了非晶氮化镓（a-GaN）薄膜. X射线衍射分析（XRD）和拉曼光谱（Raman）表明薄膜具有非晶结构. 通过椭偏光谱（SE）得到薄膜的折射率和厚度都随着氩气分量的增多而增大. 紫外—可见光谱（UV-Vis）的测量得到，当氩气分量R，即Ar/（Ar+N₂），为0%时，薄膜的光学带隙为3.90eV，比晶体GaN （c-GaN） 的较大，这主要是由非晶结构中原子无序性造成的；而当R关键词：非晶氮化镓溅射光学带隙带尾态

Optical properties of amorphous GaN films deposited by sputtering

The amorphous GaN（a-GaN） films are deposited by direct current planar magnetron sputtering in different compositions of argon-nitrogen mixtures. X-ray diffraction patterns and the Raman spectra indicate that the films have amorphous structures. Spectroscopic ellipsometry shows that the refractive index and the film thickness increase with increasing argon content. The UV-Vis spectra indicate that the band gap of the film deposited without argon is 3.90eV, which is much larger than that of crystalline GaN （c-GaN）, owing to the structural disorder. When the films are deposited at higher argon content, the band gap becomes much smaller （2.80—3.30eV）, probably because of more excessive Ga in the films. The band tails extending to lower energies are modeled. Two parameters representing the energy broadening of the electronic transitions and the width or slope of the exponential tail are 0.257—0.338eV and 1.44—1.89?eV, respectively, which are higher than that of c-GaN films, indicating that a-GaN films have wider absorption tails than the c-GaN films. Photoluminescence peak at 360 nm observed at room temperature comes from band_to_band emission.
Keywords：amorphous GaNsputteringabsorptionband tail