【摘要】：以GaN為代表的寬禁帶III族氮化物在高能、高頻、功率以及光電器件中有重要的應用的價值。由于晶體結構中心不對稱,材料中存在著強的自極化效應�；诖�,本文主要研究寬禁帶III族氮化物的極化特性,以及極化效應在寬禁帶III族氮化物基器件中的應用。首先,本文介紹了第一性原理計算方法和理論模型,利用CASTEP軟件包基于第一性原理計算,研究了GaN和AlGaN的能帶結構以及電子態(tài)密度。分析了價電子處在的能級位置。利用DOML軟件包基于第一性原理計算,研究了GaN/AlN超晶格中極化效應對電子態(tài)密度以及電荷分布的影響。在極化效應的作用下,Ga原子處于價帶底的3d態(tài)電子躍遷到上價帶頂和導帶中。在異質結的結面處,出現了正電荷和負電荷堆積現象。通過自洽求解薛定諤方程和泊松方程,研究了極化效應對AlGaN/GaN異質結中二維電子氣的作用。無需雜質摻雜,利用極化誘導摻雜獲得了濃度為1019cm-3量級的二維電子氣。總結了不同Al組分和不同AlGaN薄膜厚度,極化誘導二維電子氣濃度和分布變化的規(guī)律。深入的研究了極化誘導摻雜提高寬禁帶III族氮化物摻雜效率的問題。無需雜質摻雜,沿[0001]晶向方向,線性的增加AlGaN薄膜Al的組分,獲得了電子濃度達到1019cm-3量級的n型AlGaN薄膜。無需雜質摻雜,在Si襯底上制備出具有二極管電學特性的極化誘導摻雜的高Al組分AlGaN基PN結。最后運用Silvaco軟件中的ATLAS半導體器件仿真器,分析了極化效應對AlGaN基紫外LED發(fā)光效率的影響。由極化效應產生的極化電場,導致能帶彎曲,電子空穴波函數空間分離,溢出電流增加。對N-face AlGaN基紫外LED的光學特性和輻射光譜進行了研究,并與Ga-face AlGaN基紫外LED對比。在N-face AlGaN紫外LED中引入了階梯結構的電子注入層。通過分析光譜、電流-輸出光功率特性曲線、能帶結構圖以及載流子輻射復合速率,結果表明相對于Ga-face的紫外LED,N-face的紫外LED具有更好的光學性能,階梯結構的電子注入層可以有效的降低溢出電流,提高紫外LED的發(fā)光效率。
[Abstract]:The wide band gap III nitrides, represented by GaN, have important applications in high energy, high frequency, power and optoelectronic devices. Due to the asymmetry of crystal structure center, there is a strong self-polarization effect in the material. Based on this, the polarization characteristics of wide band gap III group nitride and the application of polarization effect in wide band gap III family nitride based devices are studied in this paper. Firstly, the first principle calculation method and theoretical model are introduced. The energy band structure and electronic density of states of GaN and AlGaN are studied by using CASTEP software package based on first principle calculation. The energy level position of valence electron is analyzed. The effects of polarization on the density of states and charge distribution in GaN/AlN superlattices have been studied by using DOML software package based on first-principles calculations. Under the effect of polarization, the electrons in the 3D states of Ga atoms at the bottom of the valence band transition to the top of the upper valence band and the conduction band. At the junction surface of the heterojunction, positive charge and negative charge stacking appear. By self-consistent solution of Schrodinger equation and Poisson equation, the effect of polarization effect on two-dimensional electron gas in AlGaN/GaN heterojunction is studied. Without impurity doping, two dimensional electron gas with concentration of 1019cm-3 was obtained by polarization induced doping. The changes of concentration and distribution of two-dimensional electron gas induced by polarization with different Al components and different thickness of AlGaN films were summarized. The effect of polarization induced doping on the efficiency of wide band gap III nitride doping was studied. Without impurity doping and along the direction of [0001] crystal direction, the composition of Al in AlGaN thin films was linearly increased, and n-type AlGaN films with electron concentration of 1019cm-3 order were obtained. Polarization-induced doped AlGaN based PN junctions with diode electrical properties were fabricated on Si substrates without impurity doping. Finally, using the ATLAS semiconductor device simulator in Silvaco software, the effect of polarization effect on the luminescence efficiency of AlGaN based UV LED is analyzed. The polarized electric field produced by the polarization effect results in the band bending, the separation of the electron hole wave function in space, and the increase of the overflow current. The optical properties and radiation spectra of N-face AlGaN based UV LED were studied and compared with Ga-face AlGaN based UV LED. An electron injection layer with step structure was introduced into N-face AlGaN UV LED. By analyzing spectrum, current-output optical power characteristic curve, band structure diagram and carrier radiation recombination rate, the results show that the UV LED of Ga-face has better optical performance than the UV LEDN-face of Ga-face. The electron injection layer with step structure can effectively reduce the overflow current and improve the luminescence efficiency of UV LED.
【學位授予單位】：電子科技大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TN304

【相似文獻】

相關期刊論文 前10條

1 趙建芝;林兆軍;Corrigan T D;張宇;李惠軍;王占國;;Influence of annealed ohmic contact metals on electron mobility of strained AlGaN/GaN heterostructures[J];半導體學報;2009年10期

2 孫再吉;;開發(fā)插入AlGaN層的InAlN/AlGaN/GaN FETs[J];半導體信息;2010年04期

3 任凡;郝智彪;王磊;汪萊;李洪濤;羅毅;;Effects of SiN_x on two-dimensional electron gas and current collapse of AlGaN/GaN high electron mobility transistors[J];Chinese Physics B;2010年01期

4 紀攀峰;劉乃鑫;魏同波;劉U，

本文編號：2142806