采用X射线光谱R(XPS)和椭偏测试仪(SE)对GaN材料干氧氧化所得氧化物薄膜的组分、厚度、光学常数等物理特性进行了研究.当氧化温度为900℃、氧化时间为15～240min时,XPS测试结果表明,所得氧化物类型为Ga_2O_3,且由于大量O空位的存在,其表面Ga/O比率约为1.2.SE测试结果表明,GaN线性氧化速率约为40nm/h,呈抛物线生长,最终平均氧化速率约为25nm/h.在300～800nm测试范围内,Ga_2O_3折射率为1.9～2.2,与文献测试结果相符.但在300～400nm测试范围内存在反常色散现象,这与GaN在此波段的强吸收有关.
The physical characteristics such as composition, thickness and optical constant of the oxide thin films are investigated by X-ray photoelectron spectrocopy (XPS) and spectroscopic ellipsometry (SE). XPS spectra of Ga_(3d) and O_(1s), core levels indicate that the thermal oxide is gallium oxide (Ga_2O_3) and the ratio of Ga to O is about 1.2 which is induced by the existence of much oxygen loss. SE metrical results indicate the linear grown rate is ～40nm/h and the average grown rate is ～25nm/h. The refractive index of Ga_2O_3 is 1.9～2.2 in the wavelength range of 300～800nm which agree with the previous study results. However, The anomalous refractive phenomenon appeares at 300～400nm, the reason is probably interrelated with the strong absorbance of GaN in this wavelength range and needs to study deeply in the future.
参考文献
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