本文選題：氮化物 + 極化��； 參考：《北京科技大學(xué)》2016年博士論文

【摘要】：極化效應(yīng)是Ⅲ族氮化物材料最鮮明的特點(diǎn)之一,在Ⅲ族氮化物微電子和光電子器件中扮演著十分重要的角色。GaN HFET (Heterojunction Field Effect Transistor,HFET)的工作基礎(chǔ)正是AlGaN/GaN突變結(jié)界面由于極化效應(yīng)產(chǎn)生的二維電子氣。當(dāng)AlGaN/GaN異質(zhì)結(jié)界面材料組份呈漸變狀態(tài),極化效應(yīng)產(chǎn)生的極化強(qiáng)度就會(huì)隨之漸變,進(jìn)而在組份漸變的AlGaN中就會(huì)出現(xiàn)由極化產(chǎn)生的呈三維分布的自由電子。這種由極化效應(yīng)導(dǎo)致材料中存在大量三維分布的自由載流子的現(xiàn)象被稱(chēng)作極化摻雜。這種新穎的摻雜形式和載流子分布方式給GaN基電子器件設(shè)計(jì)帶來(lái)更多的選擇,如極化摻雜場(chǎng)效應(yīng)晶體管(Polarization Doped Field Effect Transistor,PolFET)。相較于傳統(tǒng)的氮化物電子器件,基于極化摻雜的PolFET表現(xiàn)出迥然不同的器件特性,具有高線性度、高可靠性等諸多特點(diǎn)。本論文以MOCVD (Metal Organic Chemical Vapor Deposition, MOCVD)制備氮化物材料為基礎(chǔ),系統(tǒng)研究了氮化物材料生長(zhǎng)、AlGaN/GaN PolFET器件的設(shè)計(jì)、制備和器件性能。研究了GaN外延材料生長(zhǎng)中的工藝優(yōu)化,包括緩沖層的優(yōu)化、生長(zhǎng)工藝參數(shù)的調(diào)整、GaN外延層應(yīng)力控制等。經(jīng)過(guò)優(yōu)化, SiC襯底上GaN外延層(002)和(102)面的X射線搖擺曲線半高寬分別達(dá)到185 arcsec和261arcsec,并提出SiC襯底上GaN外延應(yīng)力變化模型。使用MOCVD方法制備了組份漸變的AlGaN/GaN材料,體摻雜濃度1.2E+18 cm-3,遷移率達(dá)到732 cm2/V·s。使用二次離子質(zhì)譜進(jìn)行了組份分析,發(fā)現(xiàn)自表面起A1組份由35%到0%單調(diào)變化,正是組份的線性變化引起的極化梯度導(dǎo)致了緩變AlGaN層中自由電子準(zhǔn)體三維分布。使用變頻電導(dǎo)-電壓測(cè)試表征了該組份漸變的AlGaN/GaN材料的陷阱行為。與傳統(tǒng)的突變AlGaN/GaN異質(zhì)結(jié)構(gòu)中存在大量的陷阱堆積相比,在緩變AlGaN/GaN異質(zhì)結(jié)中沒(méi)有發(fā)現(xiàn)明顯的陷阱堆積,這是因?yàn)榫徸兘Y(jié)材料消除了脆弱的突變異質(zhì)界面。另外,在緩變AlGaN/GaN結(jié)構(gòu)中觀察到陷阱時(shí)間常數(shù)與偏置電壓呈線性指數(shù)關(guān)系,這是界面陷阱的典型特征,說(shuō)明緩變AlGaN/GaN異質(zhì)結(jié)構(gòu)具有多界面特性。基于緩變AlGaN/GaN異質(zhì)結(jié)材料制備了高線性AlGaN/GaN PolFET器件。在5V柵壓工作范圍內(nèi),AlGaN/GaN PolFET器件的直流和射頻特性均對(duì)偏置點(diǎn)不敏感,非常適合WiMAX和LTE-Advanced等無(wú)線通信系統(tǒng)的線性放大器等應(yīng)用。采用動(dòng)態(tài)Ⅰ-Ⅴ測(cè)試表征了AlGaN/GaN PolFET器件的陷阱行為,相較于傳統(tǒng)的基于突變結(jié)材料的AlGaN/GaN HFET中較大的電流崩塌,基于緩變結(jié)材料的AlGaN/GaN PolFET器件呈現(xiàn)出極小的電流崩塌行為。通過(guò)模擬仿真進(jìn)行了該現(xiàn)象的機(jī)理分析,緩變組份AlGaN材料拓寬了電子溝道,而AlGaN緩變材料中含有大量可移動(dòng)電子,屏蔽了溝道中下半部分載流子與表面陷阱的作用,從而抑制了PolFET器件的電流崩塌。進(jìn)行了AlGaN/GaN PolFET器件直流高溫特性研究。發(fā)現(xiàn)隨著溫度的升高,器件的漏極電流和跨導(dǎo)都單調(diào)下降。相較于傳統(tǒng)AlGaN/GaN基HFET, PolFET的漏極電流下降幅度更小。AlGaN/GaN PolFET器件不同柵偏置下的跨導(dǎo)下降行為表現(xiàn)出不同的溫度依賴(lài)關(guān)系,當(dāng)柵壓為-2V時(shí),跨導(dǎo)下降的溫度系數(shù)為-0.5,而柵壓為-5 V時(shí),跨導(dǎo)下降溫度系數(shù)為-1.5。研究了AlGaN/GaN緩變異質(zhì)結(jié)材料中不同空間位置載流子的輸運(yùn)規(guī)律,從AlGaN/GaN PolFET獨(dú)特的載流子行為出發(fā),提出準(zhǔn)多溝道模型對(duì)PolFET的高溫特性進(jìn)行了分析
[Abstract]:Polarization effect is one of the most distinct characteristics of nitride materials, which plays a very important role in.GaN HFET (Heterojunction Field Effect Transistor, HFET) in the third group of nitride microelectrons and optoelectronic devices. The basis of the working basis is the two-dimensional electron gas produced by the polarization effect of the AlGaN/GaN junction interface when the AlGaN/GaN is different. The material components of the mass interface are gradually changing, and the polarization intensity of the polarization effect will gradually change, and then there will be a three-dimensional free electron produced by polarization in the AlGaN of the component gradually. This phenomenon is called polarization doping in the phenomenon of a large number of three dimensional distribution in the material. New types of doping and carrier distribution bring more options for the design of GaN based electronic devices, such as polarization doped field effect transistors (Polarization Doped Field Effect Transistor, PolFET). Compared with traditional nitride electronic devices, polarization based PolFET shows very different device characteristics and high lines. On the basis of MOCVD (Metal Organic Chemical Vapor Deposition, MOCVD) preparation of nitride materials, this paper systematically studies the growth of nitride materials, the design, preparation and performance of AlGaN/GaN PolFET devices, and studies the process optimization in the growth of GaN epitaxial materials, including the optimization of the buffer layer. The adjustment of the growth process parameters, the stress control of the GaN epitaxial layer, and so on. After optimization, the X ray rocking curve of the GaN epitaxial layer (002) and (102) surface on the SiC substrate is 185 arcsec and 261arcsec respectively, and the GaN epitaxial stress change model on the SiC substrate is put forward. The AlGaN/GaN material of the component gradual change is prepared by the MOCVD square method, and the volume doping concentration is 1.. 2E+18 cm-3, the mobility of 732 cm2/V. S. was analyzed by two ion mass spectrometry. It was found that the A1 component from the surface was monotonically changed from 35% to 0%. It was the polarization gradient caused by the linear variation of the components that resulted in the three-dimensional distribution of the free electron quasi body in the slowly changing AlGaN layer. The trap behavior of lGaN/GaN material. Compared with a large number of traps in the traditional mutant AlGaN/GaN heterostructure, there is no obvious trap accumulation in the slowly changing AlGaN/GaN heterojunction. This is because the slow transition material eliminates the fragile mutation heterogeneous interface. In addition, the trap time constant is observed in the slowly changing AlGaN/GaN structure and the trap time constant is observed. The bias voltage has a linear exponential relationship, which is a typical feature of the interface trap. It shows that the slow variant AlGaN/GaN heterostructure has multiple interface characteristics. A high linear AlGaN/GaN PolFET device is prepared based on the slowly varying AlGaN/GaN heterojunction material. The DC and RF characteristics of the AlGaN/GaN PolFET devices are not sensitive to the bias point in the 5V gate voltage range. It is very suitable for applications of linear amplifiers such as WiMAX and LTE-Advanced wireless communication systems. The trap behavior of AlGaN/GaN PolFET devices is characterized by dynamic I-V test. Compared to the larger current collapse in the AlGaN/GaN HFET based on the traditional mutant junction material, the AlGaN/GaN PolFET device based on the retarded junction material is very small. The mechanism analysis of the phenomenon is carried out by simulation. The slow variable component AlGaN material widens the electronic channel, while the AlGaN slowly varying material contains a large number of movable electrons, shielding the role of the carrier and surface traps in the middle and lower part of the channel, thus inhibiting the current collapse of the PolFET device. AlGaN/GaN PolFET has been carried out. It is found that the leakage current and transconductance of the device decrease monotonically with the increase of temperature. Compared to the traditional AlGaN/GaN based HFET, the drop of the leakage current of the PolFET is smaller than that of the.AlGaN/GaN PolFET device under different gate bias. When the temperature coefficient is -0.5 and the gate pressure is -5 V, the transconductance drop temperature coefficient is -1.5. to study the transport law of different space carriers in the AlGaN/GaN slowly varying heterojunction material. From the unique carrier behavior of AlGaN/GaN PolFET, the quasi multi channel model is proposed to analyze the high temperature characteristics of PolFET.
【學(xué)位授予單位】：北京科技大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2016
【分類(lèi)號(hào)】：TQ126.2;TN386

【參考文獻(xiàn)】

相關(guān)期刊論文 前1條

1 李世彬;肖戰(zhàn)菲;蘇元捷;姜晶;居永峰;吳志明;蔣亞?wèn)|;;極化誘導(dǎo)實(shí)現(xiàn)AlGaN薄膜材料中的超高電子濃度(10~(20)cm~(-3))摻雜[J];物理學(xué)報(bào);2012年16期

，

本文編號(hào)：1902764