【作者】 李述体；

【导师】 江风益；

【作者基本信息】 南昌大学 ， 材料物理与化学， 2002， 博士

【摘要】 宽禁带III-Ⅴ族氮化物半导体材料在短波长高亮度发光器件、短波长激光器、光探测器以及高频和大功率电子器件等方面有着广泛的应用前景。自1994年日本日亚化学工业公司率先在国际上突破了GaN基蓝光LED外延材料生长技术以来,美、日等国十余家公司相继报导掌握了这项关键技术,并分别实现了批量或小批量生产GaN基LED。尽管如此,这项高技术仍处于高度保密状态,材料生长的关键思想及核心技术仍未公开,还无法从参考文献及专利公报中获取最重要的材料生长信息。本论文就是在这种情况下立题的,旨在研究GaN基材料生长中的物理及化学问题,为生长可商品化的高亮度GaN基LED外延材料提供科学依据。本文在自制常压MOCVD和英国进口MOCVD系统上对III-Ⅴ族氮化物的生长机理进行了研究,对材料的性能进行了表征。通过设计并优化外延片多层结构,生长的蓝光LED外延片质量达到了目前国际上商品化的中高档水平。并获得了如下有创新和有意义的研究结果:1、首次提出了采用偏离化学计量比的缓冲层在大晶格失配的衬底上生长单晶膜的思想,并在GaN外延生长上得以实现。采用这种缓冲层,显著改善了GaN外延膜的结晶性能,使GaN基蓝光LED器件整体性能大幅度提高,大大降低了GaN基蓝光LED的反向漏电流,降低了正向工作电压,提高了光输出功率。2、合适的氮化衬底工艺能改善外延层的光学和电学性能;但氮化衬底条件不合适,将使外延层质量下降。研究发现不合适的氮化衬底工艺导致GaN外延膜表面粗糙的原因主要是由于这种工艺影响了后续高温GaN的生长模式,促使GaN三维生长,与有关文献报道结论不一致。3、光致发光光谱中未掺杂GaN单晶膜的2.9eV的蓝带发光机理尚未有定论。本文研究表明未掺杂GaN单晶膜出现的2.9eV的蓝带发光与补偿度有很强的依赖关系,我们把它归结为导带电子跃迁至受主能级发光(eA发光)。4、首次报导了预反应对掺硅GaN外延膜黄带发光的影响以及随掺Si量增大,GaN:Si外延膜生长速率显著下降的现象。5、研究表明:要获得高空穴载流子浓度的p型GaN,Mg的掺杂量必须适中。更多还原

【Abstract】 GaN based Ⅲ-Ⅴ nitrides have potential applications on high brightness LEDs, shortwavelength lasers, ultraviolet detectors, high temperature and high power electronicdevices. Study on physics issues and technologies of nitrides open a new area of 3thgeneration semiconductor.More than ten companies in America and Japan reported to have developed thenitrides growth technology since Nichia company in Japan first realized thecommercialization of GaN based blue LED in 1994.In this thesis,GaN and its ternary were grown by a home-made atmosphere pressuremetalorganic chemical vapor deposition (MOCVD) and Thomas Swan 6×2” MOCVDsystems. High bright blue LED wafers were obtained by optimizing the nitrides growthtechnology and wafer structure. Some encouraging results are following as:1. We present the idea of using a buffer layer of deviation from stoichiometry formaterials growth on large lattice mismatch substrates. This idea was realized in nitridesgrowth in this thesis. The epilayer crystalline quality was improved and the dislocationdensity was decreased by using GaN low and high temperature buffer layers of deviationfrom stoichiometry. The RBS/channeling spectra exhibited that the minimum yield χminof GaN layers was just only 1.5%. The leak electric current of GaN based LED wasobviously decreased and lower than 1μA at 5 volt reverse voltage by using this new buffertechnology.2. Optimum nitridation condition can improve the optical and electrical properties ofGaN layers obviously. However, the quality of GaN layers degenerated when thenitridation condition was not proper. It was suggested the reason that the epilayer surfacebecame rough by nitridation was due to the three dimensional growth mode.3. Our research results indicated that the blue PL luminescence band in unintentionaldoped GaN layers obviously related with the compensation ratio of unintentional dopedGaN, and was described to the transition from the free electron in conduction band toacceptor levels (eA luminescence).4. Our research results indicated that the intensity of yellow band emission in GaN:Sifilms was largely influenced by the parasitic reactions in the gas phase. A decreased growthrate of GaN:Si with increasing SiH4/TMGa ratio was described. Si-doped GaN films withcarrier concentration from 1×1017cm-3 to 4×1019cm-3 can be obtained.5. The doping dose of Mg was very important to obtain high hole concentration GaNlayer. Deep donors related with Mg would form if much high Mg doping dose were used.The GaN based LED wafers whose turn-on voltage was lower than 3.6 volt were obtainedby optimum the Mg doping dose and the thermally annealed condition.6. A study indicated that H2 in precursors carrier gas obviously result in increasing thegrowth rate of InxGa1-xN films, while a deep energy level emission probably appeared.7. An appropriate In/Ga ratio was necessary to increase the indium mole fraction inInxGa1-xN layers.8. InGaN layers with the indium mole fraction of 0.26 can be obtained. The band edgeemission of this InGaN layer was 545nm. The minimum yields χmin of RBS/channeling forIn0.04Ga0.96N films was only 4.1%.9. The GaN based blue LED with the turn-on voltage of lower 3.6 volt, the leakelectric current of lower 1μA at 5 volt reverse voltage and the output power of 2.9 mWcan be stably obtained even the chip processing of LED was not optimum. The blue LEDwafers have been realized commercialization.This work was supported by 863 program in China.更多还原