TETRAHERTZ MICROWAVE GENERATORS: Heterostructure Ballistic Negative Effective Mass Generator for Tetrahertz Range

9813823 Mitin PI建议韦恩州立大学的器件模拟和建模组与布朗大学的实验器件物理组合作研究，重点研究太赫兹频率辐射的固态发生器。 这类新的设备，基于短弹道二极管，其中电流是由于负有效质量（NEM）的载流子，最初提出和数值模拟的韦恩状态组在过去的三年。 预计这些二极管将在0.1-10 THz频率范围内产生电振荡（对应于从3 mm到30 um的自由空间波长）。 与其他固态太赫兹发生器相比，这些设备的操作既不需要磁场也不需要辐射场，也不需要低频脉冲的泵浦。 最后，辐射频率可以通过二极管上的电压来调节，所需的NEM色散可以在许多半导体系统中实现。 由布朗大学团队领导的实验研究的重点是在这些系统中最容易获得和技术成熟的短基弹道二极管中制造和表征：具有量子化NEM孔的p型调制掺杂GaAs量子威尔斯。 高迁移率的二维空穴气体将在布朗大学和普林斯顿大学（曼苏尔·沙耶根的小组已经获得了高质量的空穴气体）生长。 在项目的后期阶段，当需要非常高的频率测量时，他们与喷气推进实验室建立了合作关系。韦恩州立大学的理论工作将集中在进一步发展新型结构的弹道二极管产生理论。 一种提出的器件涉及经由发射极异质结注入NEM载流子，而不是它们在自洽电场中的加速。 载流子注入能量的独立控制将使产生频率与施加到二极管的电压解耦，从而允许对所产生的辐射的频率上限明显更高。 其他提出的器件将生成机制扩展到三端结构，例如由超短栅极控制的弹道场效应晶体管。 虽然更难制造，但这种装置将允许单独控制辐射的幅度和频率。

9813823MitinThe PI's propose a collaborative research effort between a device simulation and modeling group at Wayne State University and an experimental device physics group at Brown University to focus on solid state generators of terahertz frequency radiation. This novel class of devices, based on short ballistic diodes in which current flow is due to carriers with negative effective mass (NEM), was originally proposed and numerically simulated by the Wayne State group over the past three years. These diodes are predicted to generate electric oscillations in the 0.1-10 THz frequency range (corresponding to freespace wavelengths from 3 mm down to 30 um). In contrast to other solid-state terahertz generators, the operation of these devices requires neither magnetic nor radiation fields, nor pumping by lower-frequency pulses. Finally, the radiated frequency is tunable by the voltage applied to the diode.The required NEM dispersions can be realized in a number of semiconductor systems. The thrust of the experimental research, led by the Brown University team, is to fabricate and characterize short-base ballistic diodes in the most accessible and technologically mature of these systems: p-type modulation-doped GaAs quantum wells with quantized NEM holes. The high-mobility two-dimensional hole gases will be grown both at Brown and at Princeton (where Mansour Shayegan's group has achieved high-quality hole gases). For the latter stages of the project, when very high frequency measurements will be required, they have established a collaboration with the Jet Propulsion Laboratory.The theoretical effort at Wayne State will focus on further developing the theory of ballistic diode generation for new types of structures. One proposed device involves the injection of NEM current carriers via an emitter heterojunction, instead of their acceleration in a self-consistent electric field. Independent control of carrier injection energy will decouple the generation frequency from the voltage applied to the diode, allowing for a markedly higher upper frequency limit on the generated radiation. Other proposed devices extend the generation mechanism to three-terminal structures, such as ballistic field-effect transistors controlled by an ultrashort gate. While more difficult to fabricate, such devices would permit separate control over both the amplitude and frequency of the radiation.***