AlGaN基量子结构和器件中高电流密度诱导效应的调控

It is imminent to develop high-current injection and high-power AlGaN deep-ultraviolet light-emitting device (deep-UV LED) to completely replace the conventional mercury-containing UV light source. However, due to the inherent properties of AlGaN, including strong polarization effect, strong optical anisotropy and high-activation energy of acceptor, the high-current injection will induce lattice distortion, carrier screen effect, carrier leakage, and current crowding et al. As a result, the performance of deep-UV LED is still very low. In this proposal, the fundamental physics of high current-density-induced effects and modulation methods in AlGaN quantum structures and deep-UV emission devices will be explore. The competition between current-induced stress and carrier screen effects on the interband transition, optical anisotropy in AlGaN multiple quantum wells will be systematically studied, with the aim to enhance the radiate recombination efficiency. The acceptor-activation and injection characteristics in p-type AlGaN quantum structures will be explored, and also the novel p-type doping quantum structure and carrier selected blocking structure will be designed for improving hole concentration and carrier-injection efficiency. Apart from these, based on the in-depth study of the coupling relationship of carrier, phonon, and photon in deep-UV emission devices, and a novel micro-/nano- network-like electrode which combines the metal and 2D materials will be designed and fabricated to enhance the current distribution, heat dissipation, and light extraction efficiency of deep-UV LED. Based on the studies above, high-power AlGaN deep-UV LED will be achieved.

研制无汞污染的大注入高功率AlGaN深紫外发光器件，实现全面取代传统含汞紫外光源，是目前国民经济、社会发展和生态环境面临的重要战略性任务。然而，因其具有极化效应强、光学各向异性显著以及受主激活能高等材料的本征特性，使其量子结构和器件在高电流密度注入条件下存在诸多复杂的物理问题，增加了大注入高功率器件研发的挑战。本项目拟围绕高电流密度注入所引发电流诱导晶格畸变、载流子屏蔽效应、载流子泄漏、电流拥堵等物理问题，系统开展有源区量子阱结构中高电流密度诱导晶格动力学、量子能级跃迁选择及其调控，p型掺杂量子结构中高电流密度诱导载流子离化、传输机制及其调控，深紫外发光器件结构中高密度电流诱导载流子—声子—光子相互耦合作用及其电场、热场与光场联合调控研究；从而提高空穴注入效率和载流子辐射复合效率，提高器件的电流分布均匀性、散热以及出光效率，为开发新型大注入高功率深紫外发光器件奠定基础。

研制无汞污染的大注入高功率AlGaN深紫外发光器件，实现全面取代传统含汞紫外光源，是目前国民经济、社会发展和生态环境面临的重要战略性任务。然而，因其具有极化效应强、光学各向异性显著以及受主激活能高等材料的本征特性，使其量子结构和器件在高电流密度注入条件下存在诸多复杂的物理问题，增加了大注入高功率器件研发的挑战。本项目系统开展了有源区量子阱结构中应变对极化场、能带结构、价带能态密度、量子能级跃迁选择以及电子空穴复合机制的作用规律，高Al组分AlGaN量子限域新机制，以及深紫外发光器件中电场、热场与光场三种物理场之间耦合关系等基础问题的研究，从而探索提高载流子辐射复合效率、器件的电流分布均匀性以及出光效率等新途径，并取得如下主要成果：（1）探明了AlGaN多量子阱发光不均匀主要来源于AlGaN异质外延过程中晶界处形成的张应力所导致的组分偏析现象；在此基础上，提出通过在量子阱界面处引入超薄AlN层可以有效地实现应力场的调节，从而显著提高TE偏振光比例，提高量子阱自发辐射率。（2）深入研究了高Al组分AlGaN量子限域新机制，发现轨道耦合引起的能量增益附加至能带带阶上，是高Al组分AlGaN量子阱中CH带非限域现象产生的原因；基于量子限域机制的新理解，提出通过轨道耦合工程，对轨道取向进行调控，增强量子阱的量子限域效应以提高辐射跃迁几率。进一步提出基于局域离化的单原子杂质操纵的轨道耦合工程，利用Mg局域掺杂量子阱，提高量子阱有源区室温TE偏振光比例，室低温积分强度比最大可提升5倍之多。（3）最后，在梳理深紫外发光器件中电场、热场与光场三种物理场之间耦合关系的基础上，设计并研制出具有倾斜侧壁结构的AlGaN深紫外倒装高压LED芯片，在1000mA注入电流下，其发光峰值波长为278 nm，光功率达145.7 mW，且其效率下降问题得到了显著的缓解。