磊晶成長氮化銦之光學、電學、熱學性質

Molecular beam epitaxy grown Indium nitride thin film and nanomaterials: Optical, electrical and thermal properties

魏百駿(Pai-Chun Wei)

指導教授 ： 施漢章

國立清華大學/工學院/材料科學工程學系/博士(2009年)

https://doi.org/10.6843/NTHU.2009.00399

摘要

本研究成功地利用分子束磊晶系統成長氮化銦薄膜與奈米結構，並究其光學、電學、及熱學特性。首先我們使用變溫螢光光譜來分析氮化銦光學中爭議性極高的螢光能隙。我們發現螢光能量低於 0.730 eV的樣品,隨著溫度上升會產生正常的紅移現象,然而螢光能量高於0.730 eV的樣品則會產生異常的藍移。研究發現晶格膨脹造成的光譜紅移與電子電洞費米能階分離造成的光譜藍移，能有效解釋不同載子濃度的氮化銦在光學上異常位移的原因。在電特性分析部份，我們報導氮化銦薄膜中首次發現的反光導行為。不同於傳統半導體(在光線的照明下導電度會上升)，氮化銦薄膜在光線照明下導電度呈現下降。我們根據導帶上電子散射行為以及載子在不同能階中遷移來建立模型並解釋此現象。最後，我們系統性地研究不同成長溫度及不同基板上氮化銦薄膜的熱擴散係數，並研究其熱擴散數值與薄膜厚度或成長條件的關係。我們在氮化鎵上成長1.7微米厚的氮化銦能得到0.55 cm2/s高熱擴散數值的結果顯示出，較低的結構缺陷能減少傳輸聲子的散射並增加熱擴散能力。

關鍵字

氮化銦 ； 奈米管柱 ； 光譜 ； 反光導 ； 熱擴散

並列摘要

In this thesis, we present successful growth and characterization (optical, electrical, and thermal) of InN epitaxial films and nanostructures by molecular beam epitaxy. Temperature-dependent photoluminescence (PL) spectroscopy is used as a tool to study the much controversial optical band gap in degenerate InN. Samples with PL peak on the lower and higher energy side of 0.730 eV demonstrate a normal redshift and anomalous blueshift, respectively, with increasing temperature. This can be explained effectively on the basis of a competition between a conventional red shift from lattice dilation and a blue shift of the electron and hole quasi Fermi-level separation. On the electrical characterization part, we report the first observation of negative photoconductivity behavior in InN thin films. Unlike most conventional (non-degenerate) semiconductors, that show increase in conductivity with illumination, InN shows a regular decrease. The results have been qualitatively modeled on the basis of electronic scattering in the conduction band and transitions in degenerate InN with recombination centers. Finally, a systematic thermal diffusivity (related to thermal conductivity) study in the MBE-grown InN thin films on various substrates with different growth temperatures were carried out. A high thermal diffusivity value of 0.55 cm2/s for a combined 1.7 um thick InN film suggests a lower degree of phonon scattering in our sample with fewer structural defects.

並列關鍵字

indium nitride ； nanotube ； photoluminescence ； negative photoconductivity ； thermal diffusivity

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