利用兆赫波時析頻譜研究氧化鋅和摻鎵硒化鋅薄膜的電磁特性

Abstract

利用THz-TDS不僅能了解半導體薄膜在遠紅外波段的光性，還能得到載子濃度和遷移率。此外，還能揭露微觀的載子動態機制。在本研究中，為了解決一次近似解析法遇到的困難，將近似擴寬到二次近似，最後，再將光參數代回原理論檢證模型的適用性和正確性。利用Drude-Smith模型擬合光參數值，反映了樣品的背向散射傾向。在ZnO系列樣品中，參數中的ｃ値強烈地反映出樣品的品質，且藉由許多的探討釐清了此背向散射的來源。此外，藉由雜訊分析釐清了光參數震盪的來源。而在摻雜Ga的ZnSe這一系列樣品中，ｃ値也強烈地與晶界大小相關，顯示了晶界的非均向散射性；而動量鬆弛時間則在Ga濃度大於350oC時明顯變小。

Utilizing THz-Time Domain Spectroscopy(THz-TDS) can not only help us understand optical properties of semiconductor thin films in the far-infrared range(0.4~2 THz), but also extract carrier concentration and mobility of carriers. Moreover, it can still uncover microscopic dynamics of carrier transportation. In this study, for overcoming the problem of analytical method by 1st order approximation, analytical method by 2nd order approximation is proposed to extract precise optical constants. Besides, the extracted optical constants canbe fitted well by Drude-Smith model, which reveal the carrier localization by backscattering. In the series of ZnO samples, c parameters have strong relation with sample quality. Moreover, the origins of backscattering are investigated deeply to assure that mobility of carriers is most probably dominated by grain boundary scattering. In the series of Ga:ZnSe samples varied by Ga temperatures, c parameter has strong relation with grain size and momentum relaxation time reveals isotropic scattering behavior.