AlGaN基空穴隧穿注入型深紫外LED研究

AlGaN-based deep ultraviolet light-emitting diode (DUV LED) have great prospect in water purification, sterilization and disinfection, etc. For the traditional DUV LED, however, p-type doping and ohmic contact are very difficult. As a result, the wall-plug efficiency (WPE) is generally lower than 5%, which cannot meet the demand of practical applications. In this project, a tunnel junction will be integrated into DUV LED to avoid this problem, which can effectively improve the WPE. The main contents of this study are as follows: First, for p+-AlGaN/u-AlInGaN/n+-AlGaN tunnel junction, the change rule and controlling methods of tunneling probability will be investigated to obtain high-tunneling-probability tunnel junction. Second, in order to achieve high efficiency DUV LED, effect of tunnel junction on the luminous efficiency of DUV LED as well as the improvement approaches will be investigated. Third, we will investigate the accurate controlling methods of defects, composition, and doping in the tunnel-junction DUV LED to get high-quality wafers. Fourth, effect of device structure and crystal quality on the photoelectric characteristics of the tunnel-junction DUV LED will be investigated. According to the results, the theoretical design and epitaxial growth will be further improved. Finally, tunnel-junction DUV LED with high WPE will be achieved. The implementation of this project will provide theoretical and technical support for the high-efficiency DUV LED.

AlGaN基深紫外LED在净化水源和杀菌消毒等领域具有巨大的应用前景。传统深紫外LED存在p型掺杂和p型欧姆接触难的问题，电光转换效率普遍低于5%，无法满足实际应用需求。本项目拟将隧穿结集成到深紫外LED中以规避这一问题，有效提高器件电光转换效率。具体研究内容如下：1.研究p+-AlGaN/u-AlInGaN/n+-AlGaN隧穿结中隧穿几率的变化规律及调控方法，设计出高隧穿几率的隧穿结；2.研究隧穿结对深紫外LED发光效率的影响规律及改善途径，设计出高发光效率的深紫外LED结构；3.利用高温MOCVD研究隧穿结深紫外LED中缺陷、组分和掺杂的精细调控方法，获得高质量外延片；4.通过实验研究器件结构和晶体质量对隧穿结深紫外LED光电特性的影响，反馈理论设计和材料生长，获得高电光转换效率的隧穿结深紫外LED器件。本项目的实施将为高效深紫外LED的实现提供理论和技术支撑。

本项目针对传统深紫外LED电光转换效率低的问题，从材料外延、结构设计和器件制备多个角度改善深紫外LED的电光转换效率。项目取得的成果如下：1.利用原位纳米孔洞和“之”字形宏台阶两种不同的技术路线，在蓝宝石衬底上获得了低位错密度、弱应变AlN外延层，指标(4.7E7cm-2)处于国际第一梯队，为高电光转换效率深紫外LED奠定了材料基础；2.除降低贯穿位错密度外，通过点缺陷控制思想，有效抑制深紫外量子阱中缺陷-杂质络合物发光渠道，将深紫外LED的辐射复合效率大幅提高到56%；3.通过仿真模拟实现对深紫外LED空穴注入效率的提高和电子泄漏的抑制，大幅提高了深紫外LED的载流子注入效率，从而使电注入条件下的内量子效率提升54%；4.通过优化n-AlGaN刻蚀后的欧姆接触等关键器件制备工艺，将Al组分达到60%的高Al组分n-AlGaN的比接触电阻率降低到9.52E-6Ω·cm2，实现了深紫外LED的电注入发光。最终，深紫外LED芯片(Chip on wafer)的发光功率达到15.3mW@100mA。上述研究为提高深紫外LED的电光转换效率开辟了新路径。. 项目执行期间共发表SCI论文7篇(均标注基金号)，发表会议论文4篇(2篇获得全国会议优秀论文奖)，申请发明专利5件(均已授权)，联合培养博士研究生2名(均已毕业)，诱发广东省自然科学基金和广州市自然科学基金2项，项目研究成果被国际知名媒体杂志《Semiconductor Today》以头条新闻先后报道2次，项目负责人获得“广东省科学院优秀青年科技工作者”称号。