In this letter, high power density AlGaN/GaN high electron-mobility transistors (HEMTs) on a freestanding GaN substrate are reported. An asymmetric Γ-shaped 500-nm gate with a field plate of 650 nm is introduced to improve microwave power performance. The breakdown voltage (BV) is increased to more than 200 V for the fabricated device with gate-to-source and gate-to-drain distances of 1.08 and 2.92 μm. A record continuous-wave power density of 11.2 W/mm@10 GHz is realized with a drain bias of 70 V. The maximum oscillation frequency (f_max) and unity current gain cut-off frequency (f_t) of the AlGaN/GaN HEMTs exceed 30 and 20 GHz, respectively. The results demonstrate the potential of AlGaN/GaN HEMTs on free-standing GaN substrates for microwave power applications.

深度信息在机器人、自动驾驶等领域中有着重要作用，通过深度传感器获取的深度图较为稀疏，研究人员为了补全缺失的深度信息提出了大量方法。但现有方法大多是针对不透明对象，基于卷积神经网络的强大表征能力，设计了一个双分支引导的编解码结构网络模型，通过针对透明物体的以掩码图为引导的编码分支，提升网络对透明物体特征信息的提取能力，并且使用谱残差块连接编解码部分，提高了网络训练稳定性及获取物体结构信息的能力，除此之外，还加入了注意力机制以提升网络空间和语义信息的特征建模能力。该网络在两个数据集上都达到了领先的效果。

In this work, high-stability 4H-SiC avalanche photodiodes (APDs) for ultraviolet (UV) detection at high temperatures are fabricated and investigated. With the temperature increasing from room temperature to 150°C, a very small temperature coefficient of 7.4 mV/°C is achieved for the avalanche breakdown voltage of devices. For the first time, the stability of 4H-SiC APDs is verified based on an accelerated aging test with harsh stress conditions. Three different stress conditions are selected with the temperatures and reverse currents of 175°C/100 µA, 200°C/100 µA, and 200°C/500 µA, respectively. The results show that our 4H-SiC APD exhibits robust high-temperature performance and can even endure more than 120 hours at the harsh aging condition of 200°C/500 µA, which indicates that 4H-SiC APDs are very stable and reliable for applications at high temperatures.

激光聚变有望一劳永逸地解决人类的能源问题，因而受到国际社会的普遍重视，一直是国际研究的前沿热点。目前实现激光惯性约束聚变所面临的最大科学障碍（属于内禀困难）是对内爆过程中高能量密度流体力学不稳定性引起的非线性流动的有效控制，对其研究涵盖高能量密度物理、等离子体物理、流体力学、计算科学、强冲击物理和高压原子物理等多个学科，同时还要具备大规模多物理多尺度多介质流动的数值模拟能力和高功率大型激光装置等研究条件。作为新兴研究课题，高能量密度非线性流动问题充满了各种新奇的现象亟待探索。此外，流体力学不稳定性及其引起的湍流混合，还是天体物理现象（如星系碰撞与合并、恒星演化、原始恒星的形成以及超新星爆炸）中的重要过程，涉及天体物理的一些核心研究内容。本文首先综述了高能量密度非线性流动研究的现状和进展，梳理了其中的挑战和机遇。然后介绍了传统中心点火激光聚变内爆过程发生的主要流体力学不稳定性，在大量分解和综合物理研究基础上，凝练出了目前制约美国国家点火装置（NIF）内爆性能的主要流体不稳定性问题。接下来，总结了国外激光聚变流体不稳定性实验物理的研究概况。最后，展示了内爆物理团队近些年在激光聚变内爆流体不稳定性基础性问题方面的主要研究进展。该团队一直从事激光聚变内爆非线性流动研究与控制，以及聚变靶物理研究与设计，注重理论探索和实验研究相结合，近年来在内爆重要流体力学不稳定性问题的解析理论、数值模拟和激光装置实验设计与数据分析等方面取得了一系列重要成果，有力地推动了该研究方向在国内的发展。

In this Letter, we report large-area (600 μm diameter) 4H-SiC avalanche photodiodes (APDs) with high gain and low dark current for visible-blind ultraviolet detection. Based on the separate absorption and multiplication structure, 4H-SiC APDs passivated with SiNx instead of SiO2 are demonstrated for the first time, to the best of our knowledge. Benefitting from the SiNx passivation, the surface leakage current is effectively suppressed. At room temperature, high multiplication gain of 6.5×105 and low dark current density of 0.88 μA/cm2 at the gain of 1000 are achieved for our devices, which are comparable to the previously reported small-area SiC APDs.