金属衬底上高质量AlGaN的外延生长及组分可控机制研究

AlGaN, one of the third generation semiconductor materials, is an ideal material for the preparation of ultraviolet optoelectronic device. Currently, the relatively poor heat dissipation of AlGaN-based device, the low crystalline quality and the uncontrollable composition of AlGaN that significantly restrict the development of the AlGaN-based device on sapphire substrate. Given the high thermal conductivity and the relatively small lattice mismatch between some metal and AlGaN, metal will be used as substrate for the growth of composition well-controlled AlGaN. In this project, based on the previous research foundation, the key problems, including the control mechanisms of interfacial reaction and growth defect, as well as composition in AlGaN will be discussed in depth. Epitaxial growth of composition well-controlled AlGaN film on metallic substrate will be carried out by two laser beams ablating Al and Ga targets, respectively, through adjusting their laser energies and frequencies to control the quantity of the generated Al and Ga plasmas under the nitrogen plasma atmosphere. Several technologies, such as the combination of low temperature and high temperature growth, amorphous inserted layer, etc., will be employed to release the stress, annihilate the dislocation, and improve the quality of AlGaN ultimately. By optimizing the scanning location and rate of pulsed laser through adjusting the laser ratering parameters, the homogeneous thickness film will be realized. The epitaxial growth mechanism of composition well-controlled AlGaN film grown on metallic substrate by pulsed laser deposition will be revealed by carrying out the project, which will be a guideline for the growth of high-quality AlGaN epitaxial film. Meanwhile, this work will provide a new solution for the fabrication of high-efficiency AlGaN-based device.

第三代半导体材料AlGaN是制备紫外光电器件的理想材料。针对目前蓝宝石上AlGaN基器件面临的散热差、薄膜质量较差及组分可控困难等问题，项目拟采用热导率高、与AlGaN晶格失配较小的金属作为衬底，外延生长组分可控AlGaN。项目在已有研究基础上，对金属衬底上AlGaN外延生长中界面反应及缺陷以及组分控制等关键问题进行研究。采用两束激光分别烧蚀Al和Ga靶材，通过调节两束激光的能量和频率等来控制产生的Al和Ga等离子体量，在氮等离子氛围下，实现组分可控AlGaN的外延生长；采用低温结合高温两步法、非晶插入层等释放应力、抑制位错延伸，提高AlGaN质量；采用激光光栅程序优化激光在靶材上的扫描位置及速度，获得高厚度均匀性AlGaN。通过实施本项目，将揭示组分可控AlGaN在金属衬底上的外延生长机制，指导高质量组分可控AlGaN外延生长，为发展高性能AlGaN基器件提供新思路。

AlGaN材料是第三代半导体材料的重要内容，可制备功率/射频器件、紫外探测器、紫外LED等，应用于相控阵雷达、紫外预警、紫外光疗及紫外杀菌消毒等国防和民用领域。针对目前AlGaN基器件面临材料组分调控困难、缺陷密度高及器件散热差等问题，本项目开展金属衬底上组分可控AlGaN材料生长及缺陷控制研究。首先，提出一种AlGaN材料的低温生长技术脉冲激光沉积（PLD），利用激光烧蚀靶材产生的羽辉等离子体具有较高动能，能在低温抑制金属与AlGaN之间界面反应条件下实现外延生长；再通过控制Al衬底温度和激光烧蚀GaN靶材的能量和频率，以控制Al原子进入GaN晶格的量，实现了Al组分从0～1连续变化的AlGaN生长；然后，提出了低温结合高温两步生长法和非晶插入层技术，控制应力和缺陷，提高了金属衬底上AlGaN的晶体质量缺陷密度低至E8cm-2；采用激光光栅辅助PLD技术，改变羽辉等离子体在空间的分布，提升材料的厚度均匀性，实现300nm厚AlGaN的厚度不均匀性低于1.1%。最后，将上述技术应用于III族氮化物LED和探测器，大幅提升了器件的性能；大功率LED光功率达659mW@350mA，紫外光电探测器响应度高达0.74A/W，暗电流低至1.3nA@2V。相关研究结果发表Adv. Mater. 、Adv. Funct. Mater.、Small等SCI论文27篇，申请中国发明专利11件，PCT专利6件，授权发明专利8件，其中美国专利1件；参加国内外学术会议8次；获批国家级项目3项；培养广东省杰青、中国科协青年托举人才、香江学者等青年人才，培养优秀硕博士研究生5人，毕业后就业于中科院研究所、华为等单位；培养本科生10余人，毕业后深造于日本东京工业大学、上海交通大学、复旦大学等，或就业于华星光电、TP-LINK的企业；项目技术在众拓光电等企业推广应用，产生显著经济效益，获2019年广东省技术发明一等奖（第2）、2020年中国有色金属工业科学技术奖一等奖（发明类，第2）等科研奖励。