Alloy scattering in random AlGaN alloys drastically reduces the electron mobility and therefore the power-electronics figure of merit. As a result, Al compositions greater than 75% are required to obtain even a two-fold increase of the Baliga figure of merit compared to GaN. However, beyond approximately 80% Al composition, donors in AlGaN undergo the DX transition which makes impurity doping increasingly more difficult. Moreover, the contact resistance increases exponentially with increasing Al content, and integration with dielectrics becomes difficult due to the upward shift of the conduction band. Atomically thin superlattices of AlN and GaN, also known as digital alloys, are known to grow experimentally under appropriate growth conditions. These chemically ordered nanostructures could offer significantly enhanced figure of merit compared to their random-alloy counterparts due to the absence of alloy scattering, as well as better integration with contact metals and dielectrics. In this work, we investigate the electronic structure and phonon-limited electron mobility of atomically thin AlN/GaN digital-alloy superlattices using first-principles calculations based on density-functional and many-body perturbation theory. The band gap of the atomically thin superlattices reaches 4.8 eV, and the in-plane (out-of-plane) mobility is 369 (452) cm$^2$ V$^{-1}$ s$^{-1}$. Using the modified Baliga figure of merit that accounts for the dopant ionization energy, we demonstrate that atomically thin AlN/GaN superlattices with a monolayer sublattice periodicity have the highest modified Baliga figure of merit among several technologically relevant ultra-wide band-gap materials, including random AlGaN, $β$-Ga$_{2}$O$_{3}$, cBN, and diamond.
Illumination and annealing characteristics of two-dimensional electron gas systems in metal-organic vapor-phase epitaxy grown AlGaN/AlN/GaN heterostructures
研究了两种不同Al组分（x=0.15和x=0.25）的AlGaN/AlN/GAN异质结的持续光电导（PPC）效应。利用Shubnikov-de Haas和Hall测量方法研究了AlN/GAN异质界面处形成的二维电子气。利用光学照射，我们能够将Al 0.15 Ga 0.85 N/AlN/GAN样品的载流子密度从1.6 × 10 ^{12} cm^{-2}增加到5.9 × 10 ^{12} cm^{-2}，同时在T = 1.6 K时电子迁移率从9540 cm 2/Vs增加到21400 cm 2/Vs。在这两个样品中的持续光电流表现出强烈的依赖于照明波长，是最高的接近带隙和降低在较长的波长。PPC效应对于长于530 nm的照明波长变得相当弱，并且在光谱的红外区域（>700 nm）中显示出具有初始负光电导的更复杂的响应。Al0.25Ga0.75N/AlN/GAN和Al0.15Ga0.85N/AlN/GAN样品在390 nm照射下的最大PPC效率分别为0.011%和0.005%。在光照后，可以通过退火样品来降低载流子密度。在20-280 K温度范围内研究了PPC效应的退火特性。我们发现，在280 K退火是不足以完全恢复的载流子密度。事实上，即使在室温下，PPC效应也发生在这些样品中。比较两种样品的测量结果，Al0.25Ga0.75N/AlN/GAN样品具有较大的光照响应，并显示出较小的恢复与…
Weak antilocalization and zero-field electron spin splitting in AlGaN/AlN/GaN heterostructures with a polarization induced two-dimensional electron gas
Ultraviolet Photodetectors based on GaN and AlGaN/AlN Nanowire Ensembles: Effects of Planarization with Hydrogen Silsesquioxane and Nanowire Architecture
研究 HSQ 包封平坦化的 GaN 与 AlGaN/AlN 纳米线紫外光电探测器，揭示其钝化、应变和偏压可调光谱响应机制，并验证器件保持单纳米线级选择性且无持续光电流。
AlGaN/AlN Stranski-Krastanov quantum dots for highly efficient electron beam pumped emitters: The role of miniaturization and composition to attain far UV-C emission
Barrier-channel intermixing and 2-dimensional electron gas degradation in Al-rich Al(Ga)N/AlGaN high electron mobility transistor heterostructures
Tyndall National Institute, University College Cork（廷德尔国家研究所，科克大学）；James Watt School of Engineering, University of Glasgow（詹姆斯·瓦特工程学院，格拉斯哥大学）；School of Physics, University College Cork（物理学院，科克大学）；School of Engineering, University College Cork（工程学院，科克大学）
Ultra-wide-band-gap group-III nitrides are of interest for applications in deep-ultraviolet optoelectronics and power electronics. Such devices must be able to efficiently dissipate heat generated from their operation, making the thermal conductivity of the constituent materials an important parameter for high-power applications. We have investigated the phonon-limited thermal conductivity of AlN, GaN, and Al$_x$Ga$_{1-x}$N using first-principles calculations, with a focus on the effects of compositional and isotopic disorder. Our Boltzmann-transport-equation calculations show that the maximum…
Drive high power UVC-LED wafer into low-cost 4-inch era: effect of strain modulation
紫外线-C发光二极管（UVC-LED）在各种情况下的病原体灭活中有很大的应用，特别是在抗击COVID-19方面。不幸的是，它的外延片到目前为止仅限于2英寸大小，这大大增加了大规模生产的成本。在这项工作中，我们报告了4英寸无裂纹的大功率UVC-LED晶圆。这一成就依赖于所提出的应变定制策略，其中在高温退火（HTA）-AlN模板上AlN的同质外延期间引入三维到二维（3D-2D）过渡层，其成功地将原始压缩应变驱动为拉伸应变，从而解决了实现具有平坦表面的高质量Al $_{0.6}$ Ga $_{0.4}$ N层的挑战。这种光滑的Al $_{0.6}$ Ga $_{0.4}$ N层几乎是在应变定制的HTA-AlN模板上假晶生长的，导致4英寸的UVC-LED晶片具有出色的性能。我们的策略成功地解决了在明显的结晶AlN模板上生产大尺寸UVC-LED晶片的矛盾：HTA-AlN中的压缩应变允许无裂纹的4英寸晶片，但同时导致AlGaN形态和晶体质量的恶化。4英寸晶圆的推出，使UVC-LED的芯片制造工艺与成熟的蓝光工艺相匹配，必将加速UVC-LED在日常生活中的普及。
Demonstration of Si-doped Al-rich thin regrown Al(Ga)N films on AlN on sapphire templates with $\gt10^{15}/cm^3$ free carrier concentration using close-coupled showerhead MOCVD reactor
