摘要
直至最近，氮化銦在三族氮化物當中仍是被研究的最少的。在此，我們研究以分子束磊晶法及金屬有機化學氣相沈積法所成長之高品質氮化銦薄膜之光電特性。結合理論模型計算，我們對此材料的物理特性提供更深入的瞭解。就光學特性而言：我們發現氮化銦的發光機制為位於導帶上的自由電子與位於價帶尾的非平衡電洞復合發光。其絕對零度與常溫的能隙為0.68 與0.62 電子伏特。而能隙與溫度之間的關係可以用Pässler方程式做適當的描述。對本質的氮化銦而言，Pässler參數為：α=0.55 meV K-1， Θ=576 K，及 p=2.2。就傳輸特性而言：我們發現氮化銦電子的有效質量會隨樣品之自由電子濃度上生而增加。在結合了Kane的模型和因電子-電子交互作用以及電子-游離化之缺陷交互作用所造成的能帶重新常態化效應之計算，可以對這個現象提供很好的描述。在導帶底端之電子有效質量為0.05個電子靜止質量，這個數值跟理論計算相當符合。最後，我們研究經過氫化之後的氮化銦表面形貌，傳輸特性和光學特性。我們發現樣品表面粗糙程度可因氫化作用而降低；而依氫化時間之不同，樣品之自由電子濃度可以提升或降低。光激螢光光譜之線寬可透過氫化作用降低，而發光強度倍增強大約3倍。我們提出一些可能的機制來解釋這些現象。
並列摘要
Up to the very recently, InN has been the least studied of the group Ⅲ-nitride semiconductors. In this thesis, detailed optical and transport properties of high-quality InN thin films grown by molecular beam expitaxy and metal organic chemical vapor deposition were investigated. Combining with model calculations, we provide a deeper understanding of physical properties of this material. For optical properties, we found that the photoluminescence transition mechanism in InN epifilms can be characterized as the recombination of free electrons in the conduction band to nonequilibrium holes in the valence band tail. The band gap energy at zero temperature and room temperature are 0.68 eV and 0.62 eV, respectively. The temperature dependence of the band gap energy can be well described by the Pässler equation and the parameters of intrinsic InN are α=0.55 meV K-1, Θ=576 K, and p=2.2. For transport properties, we found that the electron effective mass increases with increasing free electron concentration. Calculations based on the combination of Kane’s model and band renormalization effect due to electron-electron interaction and electron-ionized impurity interaction can provide excellent description. The effective mass at the bottom of the conduction band was found to be m* =0.05 m0, which is in good agreement with the theoretical calculation. Finally, surface morphologies, transport and optical properties of hydrogenated InN epifilms were also investigated. The average rms surface roughness decreases after hydrogenation. The free electron concentration can be increased or decreased depending on the duration of hydrogenation. The linewidth of the photoluminescence spectra can be reduced, and the peak intensity can be enhanced by about three times. These results indicated the physical properties of InN films can be improved by hydrogenation. Possible origins of the underlying mechanism have been proposed to explain the improvement.
參考文獻
延伸閱讀
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