西安电子科技大学
硕士学位论文
高Al组分AlGaN/GaN半导体材料的生长方法研究
蜻蜓是益虫吗姓名：***
申请学位级别：硕士
专业：微电子学与固体电子学
三门峡大坝指导教师：***
20100401
摘要
摘要
天津文庙
GaN基LED技术是实现半导体照明的关键技术，GaN基深紫外LED不仅具有高的白光转化效率，而且还
在医疗、净化等方面有重要的应用。然而制备深紫外LED所需的高Al组分AlGaN材料的生长、掺杂一直是限制器件发展的关键因素。
本文在此背景下展开了对GaN基深紫外LED的研究工作，主要涉及AlN、高Al组分AlGaN材料的生长，AlGaN材料的n型和p型掺杂及UV LED器件研制等多方面，主要研究成果如下：
1、成功得到了氮化物半导体材料生长的最佳缓冲层厚度值，发现过厚或过薄的低温AlN缓冲层都不利于氮化物半导体材料的生长。
在自主MOCVD系统上，脉冲生长实现了高质量的AlN材料，其XRD（002）面的半高宽最小只有43arcc，（102）面半高宽最小为228arcc。
通过对AlN基板上不同Al组分的AlGaN材料生长，得到不同Al组分AlGaN 材料生长时的应力变化关系。发现当其所受的张应力和压应力处于一种平衡的状态时，AlGaN材料有最佳的材料质量。
2、通过AlGaN/AlN 超晶格结构（SLs）提高了AlGaN材料的生长质量。发现Al0.45Ga0.55N/AlN SLs的周期厚度对Al0.45Ga0.55N材料质量有重要影响，SLs结构不仅可以阻挡位错在薄膜生长时的延伸，而且可调控薄膜中的应力；研究得到最优的SLs层厚度为7nm，并生长出了高质量的 Al0.45Ga0.55N材料，其（002）面XRD摇摆曲线的FWHM值仅为259arcc，（102）面也只有885arcc； AFM测得其表面有明显的原子台阶，粗糙度仅为0.185nm。
成功得到AlGaN材料生长时的Al组分与TMA/(TMA+TEG)的关系；发现AlGaN材料的表面粗糙度随Al组分的增加而增大；得到高质量的不同Al组分的AlGaN材料，其表面均有明显原子台阶。
3、实现了AlGaN材料的n型和p型有效掺杂。研究了Al组分对于AlGaN 材料n型掺杂的影响，研究了SiH4掺入量与n型载流子浓度的变化关系，得到精确控制AlGaN材料的n型掺杂的工艺条件。限制呼叫
通过对生长温度、Mg源掺入量及退火温度的优化，实现了AlGaN材料的p 型高质量掺杂，得到p型掺杂的Al组分为0.2的AlGaN材料的电阻率值仅为0.71Ω•cm，为此Al组分值AlGaN体材料p型掺杂的最佳值。我的家在东北歌词
采用AlGaN/GaN超晶格结构实现p型的高浓度掺杂，经过对超晶格周期厚度
高Al组分AlGaN/GaN半导体材料的生长方法研究
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的优化，发现10nm的周期为Mg:AlGaN/GaN超晶格结构p型掺杂的最佳厚度值，得到了p型材料电阻率仅为0.034Ω•cm，p型载流子浓度高达1.26×1019cm-3，这一结果比通常体材料的掺杂水平高近一个数量级。
4、在蓝宝石衬底上成功生长出不同发光波长的Al X Ga1-X N/Al Y Ga1-Y N多量子阱（MQWs）。研究了Al X Ga1-X N/Al Y Ga1-Y N量子阱的周期厚度及势垒Si掺杂对MQWs发光特性的影响，
成功生长出高质量的、波长小于300nm的UV LED全结构。采用横向结构、通过器件工艺的流片，成功获得UV LED管芯。对器件的测试结果显示，UV LED 的输出功率达到毫瓦量级。
5、经过对生长条件的优化，有效地提高了GaN材料的生长质量。其（002）面的半高宽由最初的800arcc减小到378arcc，（102）的半高宽也有1508arcc 减小到了597arcc。
采用脉冲法生长的高质量AlN为基板得到高质量的GaN材料，生长的材料表面原子台阶明显，XRD测得的（102）面半高宽降至348arcc，（002）面半高宽更是低至70arcc，为目前已报道的蓝宝石衬底上生长GaN的最小半高宽。
6、在蓝宝石衬底成功生长出AlInN/GaN异质结材料，采用脉冲法有效提高了AlInN薄膜的生长质量，并通过对TMA流量及AlN插入层厚度的优化提高了AlInN/GaN异质结的电学特性，报道的异质结迁移率可达1033 cm2/vs,2DEG面密度达1.96E+13/cm2。
7、采用多超晶格结构有效提高了r面蓝宝石衬底上的非极性a-GaN材料的生长质量。研究表明多超晶格结构可有效提高a-GaN材料的质量，消除表面的三角坑缺陷。报道了高质量的a-GaN材料，其摇摆曲线FWHM仅为695arcc。
综上所述，本文通过对生长深紫外LED所需的各关键技术的研究，得到了高质量的AlN、AlGaN材料及实现了n型、p型AlGaN材料的有效掺杂，制备出了不同发光波长的量子阱结构，外延生长了深紫外LED的全结构，得到毫瓦级功率的UV LED器件。同时，外延生长出了高质量的GaN材料、AlInN/GaN异质结材料及a面GaN材料。
关键词：MOCVD，AlN，AlGaN，UV LED，AlInN/GaN异质结，非极性GaN
Abstract
Abstract
The technology of GaN-bad LED is the key to miconductor lighting, GaN-bad deep UV LED not only has high conversion efficiency to white light, but also has wide u in medical, cleaning, and other important applications. However, obtaining high-quality materials and high doping levels are difficult for AlGaN films with high Al fraction, and limit the development of devices.
In the disrtation, the GaN-bad UV LED is studied, the major work is focus on the growth of AlN, AlGaN with high Al fraction, doping of n-type and p-type AlGaN films and fabrication of UV LED devices. The major achievements are listed.
1. The best thickness of LT-AlN buffer layer is obtained. It is found
that too thick or too thin buffer layer is damaged to the growth of nitride miconductor materials.
The method of pul MOCVD is ud in growth high-quality AlN films.
The FWHM of rocking curve of AlN (002) plane is only 43 arcc, and that of (102) plane is only 228 arcc, the materials quality has reached international advanced level.
Through the growth of AlGaN films with different Al fraction bad on AlN templates, the relation between strain and Al fraction is found. We also found that when the tensile strain and compress strain is in balance, the materials have high qualities.
说话的艺术2. The quality of AlGaN films is improving by using AlGaN/AlN superlattices. The thickness of AlGaN/AlN SLs has important effect on the quality of AlGaN films. The SLs structure can not only stop the extending of dislocations, but also can control the strain of the films. The best thickness of SLs is 7nm. The high-quality AlGaN film is obtained, which have 259 arcc FWHM of (002) plane and 885 arcc FWHM of (102) plane, the RMS of AlGaN film is only 0.185nm.
The relation between Al fraction of AlGaN and the ration of TMA/(TMA+TEG) is found in the work. W
e also find that the RMS of AlGaN films increa with increasing the Al fraction . The high-quality AlGaN films with different Al fraction are obtained, all the films have smooth surfaces.
3. The n-type and p-type AlGaN films are successfully doping. The effect of Al fraction on the n-type doping and the change of n-type carriers concentration with SiH4 flow rate are studied. The conditions for accurately controlling of the n-type doped level are obtained.
高Al组分AlGaN/GaN半导体材料的生长方法研究
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The high level doping of p-type AlGaN is successfully achieved. Through optimization of the growth temperature, Mg flow rate and annealing temperature, the p-type AlGaN film with resistivity of 0.71Ω • cm is obtained, which is the optimal results for AlGaN films with 0.2 Al fraction.
Using AlGaN / GaN SLs structure, we achieve high concentrations of p-type doping. Through optimization of SL thickness, we find 10nm is the best thickness for p-type doping of SL structure. The resistance of p-type material is only 0.034Ω • cm, and the p-type carrier concentration is as high as 1.26 × 1019cm-3, The doping level of SLs structure is high than the usual structure.
4. Al X Ga1-X N/Al Y Ga1-Y N MQWs with different lighting wavelengths are successfully achieved. The effect of thickness of MQW and Si- doping of barrier on the luminescence properties of MQWs is studied.
急诊和门诊的区别High quality UV LED with wavelength less than 300nm is successfully grown. UV LED chips with transver structure are successful fabricated. The testing results show that the output power of UV LED is a few milliwatts.
5. Through optimization of growth conditions, the quality of GaN materials is effectively improved , the FWHM of (002) plane decreas from 800arcc to 378arcc, the FWHM of (102) decreas from 1508 arcc to 597arcc.
High-quality GaN materials are grown on high-quality AlN template, the surface of GaN is smooth. FWHM of GaN (102) plane is reduced to 348arcc, and that of (102) plane is reduced to 70arcc, which is the best results as far as we know.
6. AlInN/GaN heterojunction materials are successfully grown on sapphire substrate. Pul MOCVD method improves the AlInN film growth quality effectively, By optimization of the TMA flow rate and thickness of AlN, the mobility and 2DEG density of AlInN/GaN heterojunction are up to 1033cm2/vs
and 1.96E+13/cm2 respectively, which is clo to the international rearch level.
7. The quality of a-GaN grown on r-sapphire substrate is improved by using veral superlattice. The study shows that the superlattice can eliminate the triangular defects. High-quality of a-GaN material is achieved, the value of FWHM is only 695arcc, which is in the international advanced level.
李威威In summary, this disrtation succeed in solving some key technical issues for the growth of deep UV LED , the issues include growth of high-quality AlN, AlGaN, doping of n-type and p-type AlGaN materials, growth of MQWs with different lighting wavelength and deep UV LED , fabrication of UV LED devices. Meanwhile, high quality of GaN materials, AlInN/GaN heterojunction and a- GaN have been
