EAGER: Electrothermal Investigation of Damped Bloch Transport at Extremely High Fields in Wide Bandgap Semiconductor Materials and its Exploitation for New Paradigms in...

电子设备运行的基础是电荷的运动，这是电流流动的起源。 因此，了解电荷在体材料中、穿过或沿着材料界面、以及穿过甚至更复杂的结构的传输的性质不仅是当今电子器件的开发和优化所必需的，而且对于创新过程以及对于在尺寸、速度、功率和其他性能指标方面提供上级功能的全新器件的概念来说确实是至关重要的。 在极大电场的影响下，最近的理论分析预测，新兴纤锌矿III族氮化物材料系统中微观水平上的电荷运动呈现出一种全新的特征，与在其他半导体晶体中观察到的完全不同。 具体而言，大量电子的组合影响，其单独的轨迹主要是在微观水平上振荡，共同导致宏观的负微分电阻，可以用于各种原始的高速，高功率器件的应用。 拟议的工作将在微观层面上对这种新的电荷传输模式及其在宏观层面上的影响产生透彻的理解，并提供一个坚实的理论框架，有可能为毫米波和太赫兹电子器件产生全新的范例。 拟议的研究结果将通过会议演示，在技术期刊上发表，并纳入格鲁吉亚理工学院在研究生和本科生水平教授的课程中进行传播。 格鲁吉亚技术（GT）是一个领先的教育机构，在科学和工程的代表性不足的群体。 其工程学院在授予妇女和少数民族工程学位方面领先全国，将积极鼓励代表性不足的群体参与拟议的研究。 证据提出了一个全新的和未开发的模式的电荷传输纤锌矿III族氮化物材料系统在极高的场强，高功率毫米波和太赫兹（THz）电子令人兴奋的影响。 在只有宽带隙半导体材料可以维持的高场强下，电子穿过布里渊区所需的时间在某些情况下可以接近甚至低于热电子的特征散射时间。 在这个极高的领域制度，电荷输运的特点是阻尼布洛赫振荡，粒子的速度和轨迹在真实的空间主要是振荡，零星中断的动量随机碰撞与声子，矛盾的是，导致净向前运动。 这是非常不同的教科书图片电荷传输在较低的电场强度，其中电子瞬时速度主要是热和随机取向。 此外，作为阻尼布洛赫振荡的结果，参与布洛赫输运的电子表现出负微分漂移速度，这与其他已知的负微分电阻（NDR）机制的关键不同之处在于，漂移速度在最大场强的极限下渐近地趋向于零（而不是某个有限值）。 这种负的差分漂移速度可以激发各种各样的电荷畴不稳定性，其可以用于产生高功率毫米波和THz信号。 提出的努力代表了一个彻底的理论研究的现象布洛赫运输，相关的电荷域不稳定性，其影响的设备应用程序，基于分析和半分析的方法，以及全带系综Monte Carlo模拟。

Fundamental to the operation of electronic devices is the motion of charge, which is the origin of electrical current flow. Understanding the nature of charge transport in bulk materials, across or along material interfaces, and through even more complex structures is therefore not only requisite for the development and optimization of present-day electron devices, but is indeed critical for the process of innovation and for the conception of entirely new devices offering superior functionality in terms of size, speed, power, and other performance metrics. Under the influence of extremely large electric fields, recent theoretical analysis predicts that charge motion at the microscopic level in the emerging wurtzite III-nitride material system takes on an entirely new character, radically dissimilar to that which has been observed in other semiconductor crystals. Specifically, the combined influence of a large number of electrons, whose individual trajectories are predominantly oscillatory at the microscopic level, collectively leads to a macroscopic negative differential resistance which can be exploited for diverse original high-speed, high-power device applications. The proposed work will generate a thorough understanding of this new mode of charge transport at the microscopic level, its implications at the macroscopic level, and provide a solid theoretical framework with the potential to engender entirely new paradigms for millimeter-wave and terahertz electronic devices. Results of the proposed research will be disseminated through conference presentations, publication in technical journals, and incorporated into courses taught at Georgia Tech at both the graduate and undergraduate levels. Georgia Tech (GT) is a leading institution for the education of underrepresented groups in science and engineering. Its College of Engineering leads the nation in engineering degrees awarded to women and minorities, and the participation of underrepresented groups in the proposed research will be encouraged proactively. Evidence is presented for a fundamentally new and unexplored mode of charge transport in the wurtzite III-nitride material system at extremely high field strengths, with exciting implications for high-power millimeter-wave and terahertz (THz) electronics. At the high field strengths which only wide bandgap semiconductor materials can sustain, the time required for electrons to traverse the Brillouin zone can in some cases approach and even fall below the characteristic scattering time for hot electrons. In this extremely high field regime, charge transport is characterized by damped Bloch oscillation, for which particles velocities and trajectories in real space are predominantly oscillatory, with sporadic interruption by momentum-randomizing collisions with phonons which, paradoxically, lead to a net forward motion. This is very different from the textbook picture of charge transport at lower field strengths, in which electrons instantaneous velocities are predominantly thermal and randomly-oriented. Moreover, electrons participating in Bloch transport exhibit a negative differential drift velocity as a result of damped Bloch oscillation which is critically different from other known mechanisms for negative differential resistance (NDR) in that the drift velocity tends asymptotically towards zero (rather than some finite value) in the limit of largest field strengths. This negative differential drift velocity can excite a wide variety of charge domain instabilities that may be exploited for the generation of high-power millimeter-wave and THz signals. The proposed effort represents a thorough theoretical investigation of the phenomenon of Bloch transport, the associated charge domain instabilities, and its implications for device applications, based on analytic and semi-analytic methods, as well as electrothermal full-band ensemble Monte Carlo simulation.