Minority Carriers in Graphene/SiC Schottky Emitter Bipolar Phototransistors for High Gain Visible Blind UV Detection

用于高增益可见光盲紫外检测的石墨烯/SiC 肖特基发射极双极光电晶体管中的少数载流子

• 批准号: 1711322
• 负责人: MVS Chandrashekhar
• 金额: $ 37万
• 依托单位: University of South Carolina at Columbia
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-08-01 至 2021-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1711322&HistoricalAwards=false
• 关键词: Minority; Carriers; Graphene; SiC; Schottky

This grant supports the University of South Carolina in the effort to understand the optical response of electronic junctions formed between silicon carbide (SiC) and epitaxial graphene layers. In particular, the PIs have demonstrated ultraviolet (UV) photodetection with high gain in devices featuring a transparent epitaxial graphene (EG) emitter grown on a p-type SiC base epilayer on n-type SiC substrates. Ultraviolet (UV) detection is an important capability for military, industrial, chemical, and biological applications. However, UV makes up only a small portion of the daylight spectrum and visible light absorption can easily overwhelm the typical UV signal, making the inherent visible blindness found in wide-bandgap semiconductors (such as SiC) therefore a desirable quality for UV detectors if architectures with high detectivity and UV-transparent contacts (such as epitaxial graphene) can be identified. Accordingly this grant supports the development and study of Schottky-emitter bipolar phototransistor (SEPT) devices including detailed analysis using scanning photocurrent microscopy (SPCM). The devices rely on high-efficiency injection of minority carriers in Schottky-based devices, an unconventional process that could transform many fields of electronics from flexible displays for consumer electronics, to optoelectronics, to power electronics. For example, a graphene-emitter bipolar transistor will enable high frequency, high power, low loss operation of smartgrids, offering performance superior to that available from either traditional silicon devices, or the latest GaN or SiC devices, considered the gold-standards in power electronics. The physics of Schottky minority carrier injection would be transformative in developing hole-injectors for light-emitting diodes (LEDs), currently a challenge in materials such as GaN, enabling low-cost solid-state lighting, or in solar cells. The PIs are additionally committed to development of a diverse science and engineering workforce through graduate training and K-12 outreach. This project will directly support research workshops on solar energy and stipends for 10 students/year from historically Black colleges and universities in the Columbia, SC area, culminating in presentations at the USC Sustainability Showcase organized by Co-PI. In most Schottky junctions, thermionic emission dominates, and minority carrier injection efficiency gamma 20% is observed, insufficient for high performance devices despite the potential high speed that Schottky electrodes offer. Results at the PI's labs on the transparent epitaxial graphene (EG)/p-SiC Schottky interface have demonstrated bipolar photocurrent gain bipolar phototransistor current gain beta 100 in response to 365nm UV radiation, indicative of highly efficient minority injection (gamma 95%). This behavior is hypothesized to occur due to i) the large Schottky barrier of EG/p-SiC (2.7eV), larger than the bandgap of many materials and ii) the large ratio of the mobility of the minority carriers (electrons) to that of the majority carriers (holes) in SiC. The ultimate goal of this project is to make EG/SiC Schottky emitter phototransistors that approach or beat UV avalanche photodiode performance ~102-3A/W (365nm) at much lower voltages (~10s V vs.300 V), leading to lower dark current and noise. The PIs will use SEPT devices formed at the University of South Carolina to interrogate the transport of minority carriers at Schottky junctions using frequency, time, spatially resolved optical measurements, as well as temperature dependent DC measurements. The use of the only natively grown Schottky interface EG/SiC enables systematic tuning of the interfacial properties using H-intercalation, and by exposure to polar gas ambients such as H2O, NO2 and NH3, which the PIs will use to control minority carrier injection. They will also investigate the role of stacking fault formation under bipolar injection, a key aging process, as well as how stacking faults determine the responsivity, speed, and visible rejection of the devices. Finally, the project will permit continued collaboration with the Naval Research Laboratory.

这笔赠款支持南卡罗来纳大学了解碳化硅 (SiC) 和外延石墨烯层之间形成的电子结的光学响应。特别是，PI 已在具有在 n 型 SiC 衬底上的 p 型 SiC 基底外延层上生长的透明外延石墨烯 (EG) 发射器的器件中展示了高增益的紫外 (UV) 光电检测。紫外线 (UV) 检测是军事、工业、化学和生物应用的一项重要功能。然而，紫外线仅占日光光谱的一小部分，可见光吸收很容易压倒典型的紫外线信号，从而导致宽带隙半导体（例如碳化硅）固有的可见光盲性，因此对于紫外线探测器来说，如果架构是理想的质量具有高探测率和紫外线透明接触（例如外延石墨烯）可以被识别。因此，这笔赠款支持肖特基发射极双极光电晶体管（SEPT）器件的开发和研究，包括使用扫描光电流显微镜（SPCM）进行详细分析。这些器件依赖于肖特基器件中少数载流子的高效注入，这是一种非常规工艺，可以改变许多电子领域，从消费电子产品的柔性显示器到光电子产品，再到电力电子产品。例如，石墨烯发射极双极晶体管将实现智能电网的高频、高功率、低损耗运行，其性能优于传统硅器件或最新的 GaN 或 SiC 器件，被认为是电力领域的黄金标准电子产品。肖特基少数载流子注入的物理原理将在开发发光二极管 (LED) 空穴注入器方面带来变革，目前这对于 GaN 等材料或太阳能电池来说是一个挑战，可实现低成本固态照明。此外，PI 还致力于通过研究生培训和 K-12 推广来培养多元化的科学和工程人才队伍。该项目将直接支持太阳能研究研讨会，并每年为来自南卡罗来纳州哥伦比亚地区历史悠久的黑人学院和大学的 10 名学生提供津贴，最终在联合 PI 组织的南加州大学可持续发展展示会上进行演讲。在大多数肖特基结中，热电子发射占主导地位，并且观察到少数载流子注入效率为 20%，尽管肖特基电极提供了潜在的高速，但对于高性能器件来说这还不够。 PI 实验室关于透明外延石墨烯 (EG)/p-SiC 肖特基界面的结果表明，双极光电流增益双极光电晶体管电流增益 beta 100 响应 365 nm 紫外线辐射，表明高效少数注入（伽玛 95%）。假设这种行为的发生是由于 i) EG/p-SiC (2.7eV) 的肖特基势垒大于许多材料的带隙，以及 ii) 少数载流子（电子）的迁移率与该势垒的比率较大SiC 中的多数载流子（空穴）。该项目的最终目标是使 EG/SiC 肖特基发射极光电晶体管在低得多的电压（~10s V 与 300 V）下接近或超越紫外雪崩光电二极管的性能~102-3A/W (365nm)，从而实现更低的暗值电流和噪声。 PI 将使用南卡罗来纳大学的 SEPT 设备，通过频率、时间、空间分辨光学测量以及温度相关的直流测量来询问肖特基结处少数载流子的传输。使用唯一本地生长的肖特基界面 EG/SiC 可以通过 H 插层以及暴露于 H2O、NO2 和 NH3 等极性气体环境来系统地调节界面特性，PI 将使用这些环境来控制少数载流子注入。他们还将研究双极注入下堆垛层错形成的作用，这是一个关键的老化过程，以及堆垛层错如何决定器件的响应度、速度和可见抑制。最后，该项目将允许与海军研究实验室继续合作。

项目成果

Excimer laser liftoff of AlGaN/GaN HEMTs on thick AlN heat spreaders

厚 AlN 散热器上 AlGaN/GaN HEMT 的准分子激光剥离

• DOI: 10.1063/5.0064716
• 发表时间: 2021-09-27
• 期刊: Applied Physics Letters
• 影响因子: 4
• 作者: Md. Didarul Alam;M. Gaevski;M. Jewel;Shahab Mollah;A. Mamun;K. Hussain;Rich Floyd;G. Simin;M. Ch;rashekhar;rashekhar;Asif Khan
• 通讯作者: Asif Khan

Trap characterization in ultra-wide bandgap Al 0.65 Ga 0.4 N/Al 0.4 Ga 0.6 N MOSHFET's with ZrO 2 gate dielectric using optical response and cathodoluminescence

使用光学响应和阴极发光对具有 ZrO 2 栅极电介质的超宽带隙 Al 0.65 Ga 0.4 N/Al 0.4 Ga 0.6 N MOSHFET 进行陷阱表征

• DOI: 10.1063/1.5125776
• 发表时间: 2019-11
• 期刊: Applied Physics Letters
• 影响因子: 4
• 作者: Jewel, Mohi Uddin;Alam, Md Didarul;Mollah, Shahab;Hussain, Kamal;Wheeler, Virginia;Eddy, Charles;Gaevski, Mikhail;Simin, Grigory;Chandrashekhar, MVS;Khan, Asif
• 通讯作者: Khan, Asif

Temperature characteristics of high-current UWBG enhancement and depletion mode AlGaN-channel MOSHFETs

高电流 UWBG 增强型和耗尽型 AlGaN 沟道 MOSHFET 的温度特性

• DOI: 10.1063/5.0031462
• 发表时间: 2020-12
• 期刊: Applied Physics Letters
• 影响因子: 4
• 作者: Mollah, Shahab;Gaevski, Mikhail;Hussain, Kamal;Mamun, Abdullah;Chandrashekhar, MVS;Simin, Grigory;Khan, Asif
• 通讯作者: Khan, Asif

An opto-thermal study of high brightness 280 nm emission AlGaN micropixel light-emitting diode arrays

高亮度 280 nm 发射 AlGaN 微像素发光二极管阵列的光热研究

• DOI: 10.35848/1882-0786/abd140
• 发表时间: 2020-12-18
• 期刊: Applied Physics Express
• 影响因子: 2.3
• 作者: Rich Floyd;M. Gaevski;Md. Didarul Alam;Samia Islam;K. Hussain;A. Mamun;Shahab Mollah;G. Simin;M. Ch;rashekhar;rashekhar;Asif Khan
• 通讯作者: Asif Khan

Ultrawide bandgap Al x Ga 1-x N channel heterostructure field transistors with drain currents exceeding 1.3 A/mm

漏极电流超过 1.3 A/mm 的超宽带隙 Al x Ga 1-x N 沟道异质结构场晶体管

• DOI: 10.35848/1882-0786/abb1c8
• 发表时间: 2020-10
• 期刊: Applied Physics Express
• 影响因子: 2.3
• 作者: Gaevski, Mikhail;Mollah, Shahab;Hussain, Kamal;Letton, Joshua;Mamun, Abdullah;Jewel, Mohi Uddin;Chandrashekhar, MVS;Simin, Grigory;Khan, Asif
• 通讯作者: Khan, Asif