【作者】 王东博；

【导师】 赵连城； 矫淑杰；

【作者基本信息】 哈尔滨工业大学 ， 材料科学与工程， 2013， 博士

【摘要】 AlxInyGa1-x-yN四元化合物半导体材料，通过调节Al和In的组分不但可以实现禁带宽度和晶格常数的独立调节，还可以与GaN缓冲层的热外延系数相匹配，更兼具AlxGa1-xN材料的禁带宽度大和InxGa1-xN材料对位错不敏感，发光效率高等优点，从而使AlxInyGa1-x-yN半导体薄膜成为高效发光二极管的研究热点并广泛受到关注。本文主要针对AlxInyGa1-x-yN四元化合物半导体材料研究的热点问题，利用MOVPE技术通过调节金属Al束流和生长温度，生长禁带宽度大，高晶体质量的AlxInyGa1-x-yN四元化合物，并通过调节生长参数成功制备了与GaN缓冲层晶格匹配的AlxInyGa1-x-yN材料，在此基础上对AlxInyGa1-x-yN四元化合物的相分离、发光机制、电-声子耦合进行了研究，制备了AlxInyGa1-x-yN基MSM紫外探测器。本论文的具体研究内容如下：在c轴蓝宝石衬底上利用MOVPE设备，通过调节金属Al束流生长了不同禁带宽度的高质量的AlxInyGa1-x-yN四元化合物半导体，并且在只调节金属Al束流的情况下，成功生长了与GaN缓冲层晶格匹配的AlxInyGa1-x-yN。通过光学、电学等一系列表征手段研究了金属Al束流对AlxInyGa1-x-yN四元化合物薄膜光电性质的影响。内量子效率测试结果表明，AlxInyGa1-x-yN四元化合物的内量子效率高于In组分近似的InxGa1-xN的内量子效率，也高于GaN缓冲层的内量子效率。在调节金属Al束流生长AlxInyGa1-x-yN的基础上，将生长温度从850oC下降到830oC，生长了AlxInyGa1-x-yN四元化合物半导体。通过光学、电学等一系列表征手段研究了生长温度对AlxInyGa1-x-yN四元化合物薄膜光电性质的影响。降低生长温度后，样品的带边发光峰强度明显提高，但是材料的晶体质量下降并且表面粗糙度上升，这是由于Al原子的迁移率低、表面粘附系数高，较低的生长温度使其不能到达晶格中适当位置而在表面形成岛状生长。对生长的不同Al组分的AlxInyGa1-x-yN四元化合物材料的相分离进行了研究。在一定组分下，Al在AlxInyGa1-x-yN四元化合物中起到相分离“催化剂”的作用，在Al组分低于14%时，材料中没有发生明显的相分离现象，在Al为18%时相分离现象明显，XRD测试表明材料中存在富In区和富Al区。对所生长的不同Al组分的AlxInyGa1-x-yN四元化合物材料的发光机制进行了研究，并分析了Al原子的注入对发光机制的影响。光致发光谱测试结果表明：在一定组分下，我们所生长的AlxInyGa1-x-yN四元化合物的发光强度随禁带宽度的增大而增强，即我们获得了禁带宽度大，发光强度高的AlxInyGa1-x-yN四元化合物材料。变温发光谱表明AlxInyGa1-x-yN四元化合物带边发光峰位随温度变化呈现“S”型，说明样品中存在载流子局域机制。结合相分离分析表明：由于AlN、InN晶格常数和键能差距很大，在AlxInyGa1-x-yN中只有在Al或In组分很小的时候材料中才存在固熔区。一定组分下，AlxInyGa1-x-yN四元化合物材料随Al组分的升高，材料中组分不均匀，相分离的趋势增强。由此形成富In的In纳米簇，并造成材料能带变化，在势能最低处形成局域能级，局域能级将激子束缚住，从而避免了位错等非辐射中心的捕获，并且提高相邻激子波函数的重叠几率，激子波函数重叠几率的提高意味着辐射复合几率的提高，因此材料对于位错不敏感，在禁带宽度增大，位错密度提高后，材料仍有很高的发光强度。拉曼测试结果验证了以上结论，拉曼散射谱中存在In纳米簇声子峰，并且In纳米簇的声子峰强度随Al组分的升高而增强。对所生长的AlxInyGa1-x-yN四元化合物材料中电-声子之间相互作用进行了研究，并对所生长的InxGa1-xN和AlxInyGa1-x-yN材料声子发光峰的黄昆方程进行了计算，分别求出了In0.03Ga0.97N和Al0.15In0.03Ga0.82N的黄昆因子。计算结果表明：Al0.15In0.03Ga0.82N的黄昆因子大于相同In组分In0.03Ga0.97N的黄昆因子，并且这两种材料的黄昆因子也都大于非掺GaN体材料的黄昆因子。这种情况说明，GaN，InxGa1-xN， AlxInyGa1-x-yN三种材料中，随材料体内无序程度的加剧，除了受激载流子的局域作用加强之外，声子的局域振动也加强，这将导致电-声子之间的作用逐渐加强，这种现象体现在光致发光谱中主要是发光峰向短波长方向扩展（声子伴线的出现），以及0级声子峰和声子伴线发光强度增强。在Al0.40In0.02Ga0.58N外延膜上通过标准光刻工艺，制备了Al0.40In0.02Ga0.58N金属-半导体-金属（MSM）结构紫外探测器。并对探测器的暗电流和光谱响应特性进行了深入分析。I-V测量表明器件展现明显的肖特基二极管特性，势垒高度为0.98eV。在10V偏压下探测器的截止波长为310nm峰值响应为0.065A/W。并且在10V偏压下，探测器的可见-紫外比（R295nm/R450nm）接近两个数量级。探测器在360nm处的响应来源于GaN，这表明探测器在紫外波段可作为双波段探测器。更多还原

【Abstract】 AlxInyGa1-x-yN quaternary alloys have attracted considerable attention as ultraviolet (UV) light-emitting material. By varying aluminum and indium compositions, the band gap and lattice constant can be independently changed， which can be helpful to reduce dislocation density as well as piezoelectric field. Moreover, it provides much better insight into the growth process, in particular it allows to modulate the thermal expansion coefficient of AlxInyGa1-x-yN for matching better with GaN than its ternary counterparts, which is an important advantage in epitaxial growth. According to the present research hotspots and difficulties on AlxInyGa1-x-yN quaternary alloys, we pay more attention to the MOVPE growth of high qulity and large bandgap AlxInyGa1-x-yN quaternary alloys, through adjusting the TMAl flow rate and growth temperature. The phase separation, luminous mechanism and electron-phonon interaction of AlxInyGa1-x-yN quaternary alloys were researched in details. The details are as follows:AlxInyGa1-x-yN quaternary alloys have been grown through MOVPE on sapphire by adjusting the TMAl flow rate. Furthermore the AlxInyGa1-x-yN quaternary alloys with lattice constant match with GaN buffer have been achieved through only adjusting the TMAl flow rate. The effect of the TMAl flow rate on the optical and electrical properties of AlxInyGa1-x-yN quaternary alloys were researched. The measurement result shown the Internal quantum efficiency of AlxInyGa1-x-yN quaternary alloys was higher than InxGa1-xN and GaN.AlxInyGa1-x-yN quaternary alloys have been grown through MOVPE on sapphire by adjusting the growth temperature. The effect of the growth temperature on the optical and electrical properties of AlxInyGa1-x-yN quaternary alloys were researched. As the growth temperature reduced, the emission peak intensity of AlxInyGa1-x-yN quaternary alloys enhanced obviously, while the surface RMS of increased suddenly. We believed that this is due to the low migration and high degree of surface adhesion of Al atoms, when the temperature reduce, the Al atoms can’t reach the proper position in lattice, and then formed the island growth in surface.The phase separation of AlxInyGa1-x-yN quaternary alloys were researched in details. n. For sample1, with a lower Al content (14%), there is no obvious phase separation observed. While for sample2, as the Al content increasing to18%， phase separation was formed， which might result in the formation of In-rich clusters. The simulation result by ab initio method also shows similar results. Indium content was kept at3%in that work, when the Al content increasing from8%to15%, there is no phase separation, as the Al content increasing from15%to20%, indium-rich regions were formed in the film, which indicated the occurrence phase separation with Al content increasing. The XRD results of the two samples are consistent with the previous calculation results, which demonstrate that with a comparable In content, the Al atoms play as a “catalyst” to the phase separation process in AlxInyGa1-x-yN quaternary alloys.Luminous mechanism of AlxInyGa1-x-yN quaternary alloys were researched in details. Strong phase separation in the AlxInyGa1-x-yN quaternary alloys was observed as the Al content increased, especially In-rich phase segregation. The situation here is similar to the existence of In nanoclusters in InGaN based semiconductors. At some small regions, the In-rich phase formation leads to the localized states at potential minima, which might confine the excited carriers. The localized carriers are beneficial for radiative recombination, causing the emission intensity to increase. In AlxInyGa1-x-yN film, it was reported that above a certain critical content， the Al atoms act as the “catalyst” for the phase separation process， and the In-In affinity changes increased drastically. Based on analysis above, it can be speculated that enhanced emission intensity of sample2is induced from In-cluster in the epilayer. In this case, the excitons can be localized in potential wells formed by In-nanoclusters, which enhance the overlap of neighboring excitonic wave function and large wave function overlap results in high recombination probability. Due to the existence of a large number of In-clusters in the AlxInyGa1-x-yN alloys with high Al content, therefore it can overcome the influence of a large number of defects and provide the brighter emission than that of AlxInyGa1-x-yN alloy with lower Al content.Electron-phonon interaction of AlxInyGa1-x-yN quaternary alloys were researched in details. The Huang-Rhys factor of In0.03Ga0.97N and Al0.15In0.03Ga0.82N were caculated. It can be draw that the alloy disorder has an essiontial role on the exciton-phonon interaction in AlxInyGa1-x-yN quaternary alloy. With the increasing of Al content the alloy disorder was enhanced, result in the increase both carrier localization and phonon confine which increase the ratio of exciton-phonon interaction. These sitiation reflected in the PL spectra was both the emission intensity increase of ZPL and PSB.AlInGaN film was prepared by by metalorganic vapor phase epitaxy (MOVPE). The metal semiconductor metal photodetector based on the Al0.4In0.023Ga57.7N film exhibits a. The peak responsivity of the photodetector was around290nm and a very sharp cutoff wavelenghth was at a wavelength of about310nm corresponding to the Transmission of the AlInGaN.更多还原