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.

这项资助支持南卡罗来纳州大学努力了解碳化硅（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已经证明了具有高增益的紫外（UV）光电探测，其特征在于在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。紫外线（UV）检测是军事、工业、化学和生物应用的重要能力。然而，UV仅构成日光光谱的一小部分，并且可见光吸收可以容易地压倒典型的UV信号，从而使得在宽带隙半导体（诸如SiC）中发现的固有的可见盲性因此对于UV检测器而言是期望的质量，如果可以识别具有高检测率和UV透明接触（诸如外延石墨烯）的架构。因此，该补助金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，可以将许多电子领域从消费电子的柔性显示器转变为光电子，再到电力电子。例如，石墨烯发射极双极晶体管将实现智能电网的高频率，高功率，低损耗操作，提供上级传统硅器件或最新GaN或SiC器件的性能，这些器件被认为是电力电子领域的黄金标准。肖特基少数载流子注入的物理特性将在开发用于发光二极管（LED）的空穴注入器方面具有变革性，目前这是GaN等材料的挑战，可以实现低成本固态照明或太阳能电池。PI还致力于通过研究生培训和K-12外展发展多元化的科学和工程劳动力。该项目将直接支持太阳能研究讲习班，并为南卡罗来纳州哥伦比亚地区历史上的黑人学院和大学的10名学生提供奖学金，最终在Co-PI组织的南加州大学可持续发展展示会上发表演讲。在大多数肖特基结中，电子发射占主导地位，并且观察到少数载流子注入效率γ 20%，尽管肖特基电极提供了潜在的高速度，但这对于高性能器件是不够的。PI实验室对透明外延石墨烯（EG）/p-SiC肖特基界面的研究结果表明，双极光电流增益双极光电晶体管电流增益β 100响应于365 nm UV辐射，表明高效少数注入（γ 95%）。假设发生这种行为是由于i）EG/p-SiC的大肖特基势垒（2.7eV），大于许多材料的带隙，以及ii）SiC中少数载流子（电子）的迁移率与多数载流子（空穴）的迁移率的大比率。该项目的最终目标是制造EG/SiC肖特基发射极光电晶体管，在低得多的电压（~ 10 s V vs.300 V）下接近或击败UV雪崩光电二极管性能~102- 3 A/W（365 nm），从而降低暗电流和噪声。PI将使用在南卡罗来纳州大学形成的SEPT设备，使用频率、时间、空间分辨光学测量以及温度相关的DC测量来询问肖特基结处少数载流子的传输。仅使用天然生长的肖特基界面EG/SiC能够使用H-嵌入并通过暴露于极性气体环境（例如H2O、NO2和NH3）来系统地调节界面特性，PI将使用这些极性气体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、速度和可见排斥。最后，该项目将允许继续与海军研究实验室合作。

项目成果

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
• 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

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

• DOI: 10.1063/5.0064716
• 发表时间: 2021-09
• 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. Chandrashekhar;Asif Khan

Photovoltaic and Photoconductive Action Due to PbS Quantum Dots on Graphene/SiC Schottky Diodes from NIR to UV

石墨烯/SiC 肖特基二极管上的 PbS 量子点从近红外到紫外的光伏和光电导作用

• DOI: 10.1021/acsaelm.9b00651
• 发表时间: 2019
• 期刊: ACS Applied Electronic Materials
• 影响因子: 4.7
• 作者: Kelley, Mathew L.;Letton, Joshua;Simin, Grigory;Ahmed, Fiaz;Love-Baker, Cole A.;Greytak, Andrew B.;Chandrashekhar, M. V.
• 通讯作者: Chandrashekhar, M. V.

Ultra-wide bandgap AlGaN metal oxide semiconductor heterostructure field effect transistors with high- k ALD ZrO 2 dielectric

具有高 k ALD ZrO 2 电介质的超宽带隙 AlGaN 金属氧化物半导体异质结构场效应晶体管

• DOI: 10.1088/1361-6641/ab4781
• 发表时间: 2019
• 期刊: Semiconductor Science and Technology
• 影响因子: 1.9
• 作者: Mollah, Shahab;Gaevski, Mikhail;Chandrashekhar, MVS;Hu, Xuhong;Wheeler, Virginia;Hussain, Kamal;Mamun, Abdullah;Floyd, Richard;Ahmad, Iftikhar;Simin, Grigory
• 通讯作者: Simin, Grigory

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
• 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