摻硒氮化鎵之拉曼特性研究

Abstract

我們用良好的鑑別率和較寬的波長範圍測量攙硒氮化鎵的拉曼訊號。其結 果與磷化鎵、砷化鎵、銻化鎵、氮化鋁、氮化硼比較，我們發現它們的聲 子頻率與三族元素(硼、鋁、鎵)和五族元素(氮、磷、砷)質量倒數的平方 根形成線性關係。此外，由共振拉曼散射的研究中我們可以得到氮化鎵電 子態之間的躍遷能量。結果顯示，隨著濃度的增加，縱向光學聲子(LO)會 向高頻移動並使線寬加寬。由拉曼光譜所推測出的樣品濃度與霍爾測量 (Hall measurement)所量到的結果相符。為了檢查熱效應，我們對樣品做 降溫實驗，三個聲子的拉曼作用(three phonon process)對溫度與線寬的 關係做了很好的解釋。我們用譜線模型(lineshape model)來做電腦模擬 。實驗的結果與我們模擬的結果非常接近。 Raman scattering of Se-doped GaN films has been carried out with good frequency resolution and wide wavelength coverage. The results were compared with other gallium compounds and nitride (GaP,GaAs,GaSb,AlN,BN)reported previously.We found a good linear relationship between most of the Raman shifts and the square ro- -ot of reciprocal masses of group III and V elements. Besides, resonant scatttering for GaN was observed which is related to inter-electronic-band transitions. The results show that the LO phonons shifts towards the high frequency and broadens as the concentration increases. The concentration values obtained from the Raman data and Hall measurement agree with each other. By lowering the sample temperature, the thermal effect is examined and three phonon process appears to give good account for the temperature dependence. We use the lineshape model to fit the spectra. The agreement between the experimental and calculated spectral profiles is fairly good.