【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(yīng)用的價(jià)值。由于晶體結(jié)構(gòu)中心不對(duì)稱(chēng),材料中存在著強(qiáng)的自極化效應(yīng)�；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(yīng)在寬禁帶III族氮化物基器件中的應(yīng)用。首先,本文介紹了第一性原理計(jì)算方法和理論模型,利用CASTEP軟件包基于第一性原理計(jì)算,研究了GaN和AlGaN的能帶結(jié)構(gòu)以及電子態(tài)密度。分析了價(jià)電子處在的能級(jí)位置。利用DOML軟件包基于第一性原理計(jì)算,研究了GaN/AlN超晶格中極化效應(yīng)對(duì)電子態(tài)密度以及電荷分布的影響。在極化效應(yīng)的作用下,Ga原子處于價(jià)帶底的3d態(tài)電子躍遷到上價(jià)帶頂和導(dǎo)帶中。在異質(zhì)結(jié)的結(jié)面處,出現(xiàn)了正電荷和負(fù)電荷堆積現(xiàn)象。通過(guò)自洽求解薛定諤方程和泊松方程,研究了極化效應(yīng)對(duì)AlGaN/GaN異質(zhì)結(jié)中二維電子氣的作用。無(wú)需雜質(zhì)摻雜,利用極化誘導(dǎo)摻雜獲得了濃度為1019cm-3量級(jí)的二維電子氣�？偨Y(jié)了不同Al組分和不同AlGaN薄膜厚度,極化誘導(dǎo)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(dǎo)摻雜提高寬禁帶III族氮化物摻雜效率的問(wèn)題。無(wú)需雜質(zhì)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(dá)到1019cm-3量級(jí)的n型AlGaN薄膜。無(wú)需雜質(zhì)摻雜,在Si襯底上制備出具有二極管電學(xué)特性的極化誘導(dǎo)摻雜的高Al組分AlGaN基PN結(jié)。最后運(yùn)用Silvaco軟件中的ATLAS半導(dǎo)體器件仿真器,分析了極化效應(yīng)對(duì)AlGaN基紫外LED發(fā)光效率的影響。由極化效應(yīng)產(chǎn)生的極化電場(chǎng),導(dǎo)致能帶彎曲,電子空穴波函數(shù)空間分離,溢出電流增加。對(duì)N-face AlGaN基紫外LED的光學(xué)特性和輻射光譜進(jìn)行了研究,并與Ga-face AlGaN基紫外LED對(duì)比。在N-face AlGaN紫外LED中引入了階梯結(jié)構(gòu)的電子注入層。通過(guò)分析光譜、電流-輸出光功率特性曲線、能帶結(jié)構(gòu)圖以及載流子輻射復(fù)合速率,結(jié)果表明相對(duì)于Ga-face的紫外LED,N-face的紫外LED具有更好的光學(xué)性能,階梯結(jié)構(gòu)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(xué)位授予單位】：電子科技大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類(lèi)號(hào)】：TN304

【相似文獻(xiàn)】

相關(guān)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(guó);;Influence of annealed ohmic contact metals on electron mobility of strained AlGaN/GaN heterostructures[J];半導(dǎo)體學(xué)報(bào);2009年10期

2 孫再吉;;開(kāi)發(fā)插入AlGaN層的InAlN/AlGaN/GaN FETs[J];半導(dǎo)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(jì)攀峰;劉乃鑫;魏同波;劉U，

本文編號(hào)：2142806