标题: 低温氮化镓薄膜磊晶与物理特性之研究
Growth and Characterizations of Low Temperature GaN Epilayers Using Two-Heater MOCVD Reactor
作者: 陈永翔
陈卫国
电子物理系所
关键字: 氮化镓;霍尔量测;有机金属化学气相磊晶系统;GaN;Hall measurement;MOCVD
公开日期: 2011
摘要: 本论文中使用自组式双加热有机金属化学气相沉积(MOCVD)系统成长氮化镓(GaN)薄膜,在低磊晶温度850 ℃下成长变五三比(V/III)系列样品,并利用霍尔量测、X光绕射以及光激萤光光谱,对于薄膜的电学与光学特性进行分析。
在变五三比系列中,V/III ratio从7500增加至20000,从霍尔量测得知GaN薄膜之最佳V/III ratio为10000,此时的载子浓度与载子迁移率分别为3.9x1018 cm-3以及146 cm2/Vs,而低温(19K)光激萤光光谱亦为近能带边缘发光主导。为了进一步厘清影响GaN薄膜载子迁移率的主要散射机制,进行X光绕射与变温霍尔量测实验,探讨不同散射机制的影响性。从X光绕射频谱得知差排密度并未随着V/III ratio改变有明显变化,约在2.0x109到4.9x109 cm-2之间,显示差排散射并非影响低温GaN薄膜载子迁移率的主因。透过变温霍尔实验,量测载子迁移率随温度变化与T-1/2呈现线性关系,推测影响低温GaN薄膜载子迁移率的主因为本质缺陷散射。
In this theses, we use the home-made two-heater MOCVD reactor to grow low-growth temperature(850 ℃) GaN (LT-GaN) thin films. The electrical and optical properties of these samples were investigated by Hall, X-ray diffraction and photoluminescence measurements.
Hall measurement results indicate that the optimized V/III ratio of LT-GaN thin films grown by two-heater MOCVD reactor is 10000. The carrier concentration and carrier mobility of LT-GaN thin films is 3.9x1018 cm-3 and 146 cm2/Vs. The LT-photoluminescence (19 K) result shows that the emission is dominated by near band emission.
The X-ray diffraction and temperature dependent Hall measurement (TD-Hall measurement) are employed to confirm the scattering mechanism. The X-ray diffraction spectra show that the dislocation density does not change significantly with the various V/III ratios, implying that the dislocations scattering is insignificant in V/III series of GaN films. The TD-Hall measurements indicate that the native defects scattering is the dominated scattering mechanism.
URI: http://140.113.39.130/cdrfb3/record/nctu/#GT079921509
http://hdl.handle.net/11536/49706
显示于类别:Thesis


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