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

9813823MitinThe PI建议韦恩州立大学的设备模拟和建模小组与布朗大学的实验设备物理小组合作研究太赫兹频率辐射的固态发生器。这类基于短弹道二极管的新型器件，其中电流是由负有效质量(NEM)的载流子引起的，最初是由韦恩州立大学研究小组在过去三年中提出并进行了数值模拟。这些二极管预计将在0.1-10太赫兹的频率范围内产生电振荡(对应于从3毫米到30微米的自由空间波长)。与其他固态太赫兹发生器不同，这些设备的运行既不需要磁场，也不需要辐射场，也不需要较低频率的脉冲抽运。最后，辐射频率可以通过施加到二极管的电压来调节。所需的NEM色散可以在许多半导体系统中实现。布朗大学团队领导的这项实验研究的主旨是在这些系统中最容易获得和技术最成熟的系统中制造和表征短基弹道二极管：带有量子化NEM空穴的P型调制掺杂GaAs量子井。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·沙耶根的团队已经在那里获得高质量的空穴气体)中生长。对于项目的后期阶段，当需要非常高的频率测量时，他们已经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用于新型结构的弹道二极管产生理论。一种建议的器件包括通过发射极异质结注入NEM电流载流子，而不是在自洽电场中加速它们。对载波注入能量的独立控制将使发电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进行显著更高的频率上限。其他建议的器件将产生机制扩展到三端结构，例如由超短门控制的弹道场效应管。虽然制造难度更大，但这种装置将允许对辐射的幅度和频率进行单独控制。

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.***