郑宇翔助理教授 于2011年获得台大电机系与物理系双学位学士（获八学期书卷奖），曾于2009年至美国伊利诺大学香槟分校交换一学期。2013年自台大光电所硕士班毕业，指导教授为孙启光教授。2019年取得美国麻省理工学院电机博士，指导教授为Prof. Keith Nelson。2019年加入台大电机系及台大电信所担任助理教授，2025年加入台大光电所。

郑助理教授的研究领域为太赫兹电路组件以及超快光谱学。在太赫兹电路组件方面，着重于设计D band (110-170 GHz)及J band (220-330 GHz)的放大器、混频器、倍频器等主动电路芯片，以及设计天线、滤波器、耦合器等被动电路，更开发出世界第一套太赫兹缩距远场芯片天线量测设备。在超快光谱学方面，实验室专注于0.1-2 THz的穿透及反射频谱量测，可以获得材料的复数介电参数。郑助理教授目前参与多项大型计划，以6G无线通讯感测系统开发为主，也涉及无人机及卫星之通讯应用。

郑助理教授截至2024年已发表十五篇期刊论文及五十一篇会议论文，其中包含六次学生论文奖、五次会议旅费补助及两次新闻专题报导。2019年至2022年获国立台湾大学新聘特殊优秀人才奖励。

除了研究教学外，郑助理教授的兴趣包含铁人三项运动（游泳、自行车、跑步）、业余无线电、书法等，也对动漫略有涉猎。郑助理教授经营了一个YouTube channel，欢迎同学前往观看。

Broadband InSe/MoS₂ Type-II Heterojunction Photodetector with Gate-Tunable Polarity

Professor Yuh-Renn Wu

Graduate Institute of Photonics and Optoelectronics, National Taiwan University

台湾大学光电所 吴育任教授

The development of two-dimensional (2D) van der Waals heterojunctions has opened new possibilities for advanced optoelectronic devices, particularly in broadband photodetection. In this work, we demonstrate a broadband InSe/MoS₂ type-II heterojunction photodetector with gate-tunable polarity, enabling a near-linear wavelength-dependent photocurrent peak. The vertically stacked InSe/MoS₂ heterojunction exhibits broadband detection from 400 nm to 1064 nm, with a high responsivity of 10,200 A/W at 532 nm and −1430 A/W at 1064 nm, as well as a maximum photodetectivity of 3 × 10¹³ cm Hz^-1/2 W^-1. The device displays both positive and negative photoconductivity, depending on incident light energy, and a gate-tunable polarity transition at Vg = −20 V, which induces a photocurrent peak shifting nearly linearly with wavelength.

To gain deeper insight into the underlying mechanisms, we performed Poisson and drift-diffusion simulations to model the charge carrier dynamics within the InSe/MoS₂ heterojunction. As shown in Figure 2a, our simulations successfully reproduce the experimentally observed gate-tunable photocurrent peak. The calculated potential profile (Figure 2b) confirms the presence of a type-II band alignment, where electrons and holes accumulate at the heterojunction interface. Furthermore, the simulation results (Figure 2c) reveal that the photocurrent peak is governed by the balance between electron accumulation in MoS₂ and hole accumulation in InSe, which shifts with incident wavelength and power density. Notably, our simulations also explain the negative photoresponse under infrared illumination, attributed to trap-assisted interlayer charge transfer at the heterojunction interface (Figure 2h).

These findings demonstrate the potential of gate-tunable 2D heterojunctions for high-performance optoelectronic applications, such as tunable spectrometers, reconfigurable photodetectors, and integrated photonic circuits. The ability to control the device polarity and photoresponse via gate voltage provides new opportunities for designing multifunctional optoelectronic devices.

Reference:
Wenying Zhang, Kuan-Hao Chiao, Hsin-Wen Huang, Mohamed Abid, Cormac Ó Coileáin, Kuan-Ming Hung, Ching-Ray Chang, Yuh-Renn Wu,* and Han-Chun Wu*, "Broadband InSe/MoS₂ Type-II Heterojunction Photodetector with Gate-Tunable Polarity Induced Near-Linear Wavelength-Dependent Photocurrent Peak," ACS Applied Materials & Interfaces, 2025, 17, 12941−12951. DOI: 10.1021/acsami.4c22132.

Ultra-high thermal sensors based on quantum-well heterojunction bipolar transistors

Professor Chao-Hsin Wu

Graduate Institute of Photonics and Optoelectronics, National Taiwan University

台湾大学光电所 吴肇欣教授

We are thrilled to share a groundbreaking achievement in the field of optoelectronics and high-speed device technology: the successful design and fabrication of the world’s first Darlington transistor utilizing cascaded Light-Emitting Transistors (LETs) with ultra-high thermal sensitivity.

Our research demonstrated that the single-quantum-well heterojunction bipolar transistor (SQW-HBT) exhibits a remarkable 73.23% increase in collector current (I_C) as the temperature rises from 25 ºC to 85 ºC under a base current (I_B) of 0.2 mA and a collector-to-emitter voltage (V_CE) of 2 V, a behavior contrasting the typical thermal response of conventional HBTs, as shown in Fig. 1(a) [1]. Building on these findings, we developed a modified charge-control model for multiple-quantum-well (MQW)-based HBTs, optimizing QW parameters such as number, size, width, position, and barrier width to enhance the efficiency of LETs for thermal sensor applications, as shown in Fig. 1(b) [2]. Using this model, we engineered triple-quantum-well (TQW)-HBTs that achieved a 200% increase in I_C as temperature rose from 25 ºC to 85 ºC at I_B of 1 mA and V_CE of 2 V, as shown in Fig. 1(c), marking a significant step toward high-temperature applications [3].

Leveraging these advancements, we designed a novel Darlington transistor by cascading two LETs. The LET alone demonstrated a 153% increase in I_C under temperature changes from 25 ºC to 85 ºC at I_B of 1 mA and V_CE of 4 V, while the Darlington transistor surpassed this performance, achieving a 210% increase in IC under similar conditions, as shown in Fig. 1(d). Notably, the current sensitivity of LETs reached 8.53 μA/ºC, and the Darlington transistor achieved an exceptional 26.2 μA/ºC. Additionally, the Darlington transistor reported a voltage sensitivity of 9.12 mV/ºC, significantly surpassing the performance of conventional thermal sensors [4]. Despite these achievements, challenges remain in achieving a highly linear voltage-to-temperature response due to nonlinear electron escape from the QW. To address these challenges, we proposed a QW size-dependent optimization model, achieving an optimal balance between thermal sensitivity and linearity for specific temperature ranges [5]. For instance, a QW width of 90 Å exhibited a thermal sensitivity of 1.34 mA/ºC and a linearity fitting parameter (B) of 0.67748 within a temperature range of 25 ºC to 100 ºC, as shown in Fig. 1(e).

Our team is committed to further modifying LET-based technologies to unlock their full potential as front-end components in smart thermal sensing applications. By optimizing QW structures, we aim to enhance linearity and sensitivity, paving the way for next-generation thermal sensor technologies with unprecedented performance. These achievements represent a significant leap forward in thermal-sensitive optoelectronic devices and hold immense promise for applications in smart sensing and beyond. We thank our collaborators and supporters for their contributions to this groundbreaking research.

Reference:
[1] M. Kumar, S.-J. Hsu, S.-Y. Ho, S.-W. Chang, and C.-H. Wu, “Current gain enhancement of heterojunction bipolar light-emitting transistor using staircase InGaAs quantum well,” IEEE Trans. Electron Devices, vol. 70, no. 10, pp. 5177-5183, Oct, 2023, doi:10.1109/TED.2023.3305355.
[2] M. Kumar, L.-C. Hsueh, S.-W. Cheng, S.-W. Chang, and C.-H. Wu, “Analytical modeling of current gain in multiple-quantum-well heterojunction bipolar light-emitting transistors,” IEEE Trans. Electron Devices, vol. 71, no. 1, pp. 343-349, Jan 2024, doi:10.1109/TED.2023.3289930.
[3] M. Kumar, S.-Y. Ho, S.-J. Hsu, P.-C. Li, S.-W. Chang, and C.-H. Wu, “Current gain enhancement at high-temperature operation of triple-quantum-well heterojunction bipolar light-emitting transistor for smart thermal sensor application,” IEEE Trans. Electron Devices, vol. 71, no.1, pp. 896-903, Jan. 2024, doi: 10.1109/TED.2023.3339084.
[4] M. Kumar, K.-Y. Hsueh, S.-J. Hsu, and C.-H. Wu, “Design and fabrication of novel Darlington transistor using light-emitting transistors for smart thermal sensor technology,” IEEE Electron Device Letters, vol. 45, no. 7, pp. 1365-1368, July, 2024, doi:10.1109/LED.2024.3401084.
[5] M. Kumar, S.-W. Chang, and C.-H. Wu, “Investigation of thermal sensitivity and linearity of quantum well-based heterojunction bipolar transistor,” IEEE Transactions on Electron Devices, Early Access, Nov 2024, doi: 10.1109/TED.2024.3492153.

— 资料提供：影像显示科技知识平台 (DTKP, Display Technology Knowledge Platform) —

— 整理：林晃岩教授、郭权锋 —

磁驱动光子“微型机器人”

可重构微光学组件具有许多应用，但其可调节性仍相当有限。可操纵的微型「机器人」具有可程序化功能，在微观尺度上可以达到更好的光控制效果，这是一个诱人的概念。

康乃尔大学的Conrad Smart、Tanner Pearson和同事们展示了一种磁性可程序化和易操作的绕射微光学装置（Science 386, 1031–1037; 2024）。

该结构采用深紫外光微影制程（Deep-ultraviolet lithography, DUV）和电子束微影（Electron beam lithography, EBL）以及各种沉积和蚀刻技术制造，长度范围从毫米到奈米的组件组成，以便获取机械、绕射和磁性特征。作者将这些装置称为磁控显微型机器人，或称为「微型机器人（microbots）」。

该装置透过利用薄膜机械中的奈米磁铁（见图1C）进行程序化，只需要毫特斯拉级（millitesla-scale）磁场即可驱动奈米厚度的枢轴（hinge）接头（见图1E），例如绕射面板。这种磁驱动也可用于实现装置的大规模内部重新配置。

实验架构展示了各种各样的装置，包括双面板绕射装置和使用许多组件的可调光学装置。对于透镜，焦距在没有磁场时为50 μm，但可以调整到例如在10 mT磁场下为40 μm。该团队能够实现光机械超颖材料（optomechanical metamaterials）的运动并重构装置形状。

该论文作者之一Itai Cohen告诉《自然光子学》，该团队过去五年一直致力于微型机器人研究。当他们意识到机器人的特征足够小以至于可以绕射光时，他们联系了Francesco Monticone并开始合作设计可以整合到他们的机器人平台中的光学组件。

「与先前的微型机器人相比，这些绕射机器人整合了光学组件，包括焦距可调的菲涅尔透镜、能够产生各种绕射图案的绕射表面，以及可用于增强成像分辨率的光栅。」Cohen解释。「此外，由于它们非常柔顺（柔软），透过追踪它们的变形，我们可以确定它们被压在各种物体和材料上时所受到的力。这些性能对于该领域来说都是新的。」

Cohen认为，主要挑战有两个面向。首先是建构可作为枢轴的奈米级薄膜的能力。第二，涉及制造100奈米x50奈米单畴磁性（single-domain magnets）的技术。Cohen表示，这项技术之前已经被其它人发明，掌握这种制造流程并将其与团队新开发的薄枢轴相结合，使他们能够将磁性机器人缩小到单微米级（~5微米）。Cohen指出，薄枢轴和磁铁的技术开发跨越了两个博士学位，他强调，研究生Conrad Smart必须将所有技术整合在一起，进行测试和迭代设计，直到达到预期的结果。

除了对空间特征进行成像之外，机器人还可以引导和聚焦光线。为了展示光束控制，作者研究团队制作了具有磁可调周期的微观绕射光栅（图2A）。随着施加磁场的增加，光栅面板被压缩，透过移动一阶绕射峰值来改变绕射图案（图2B）。这证明了透过机械驱动控制光束偏转的能力。此外，绕射光栅表现出对微小力的敏感性，这由施加的磁扰动下绕射峰中的正弦振荡证明（图2D），测得的力敏感性为1 pN。这些光栅还可以在表面上移动，从而实现移动、局部的光场控制（图2C）。

扩展这一概念，作者研究团队开发了一种磁可调绕射菲涅尔透镜，具有连续可调焦距（图2E）。与传统的折射光学装置不同，此变焦镜头利用磁致动器提供紧凑的设计。菲涅耳透镜由径向排列的梯形绕射面板组成，其焦距关系由公式决定。在外部磁场下，透镜结构压缩，焦距从50 μm减少到40 μm（图2F）。该技术展示了开发可调绕射光学组件的一种有前景的方法，为自适应和小型化光学系统铺平了道路。

展望未来，该团队正在努力将其中一些功能整合到他们的电子驱动机器人中。Cohen告诉《自然光子学》杂志：「这种积体化使我们能够用光来控制机器人，而不是用目前用于产生驱动机器人的磁场的六极磁铁。」「我们正在致力于设计更复杂的光学组件。最后，我们还希望将这些机器人与光纤结合起来，使外科医生能够更轻松地对现场环境进行成像。」