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

mit PI提议在韦恩州立大学的设备模拟和建模小组和布朗大学的实验设备物理小组之间进行合作研究，重点研究太赫兹频率辐射的固态发生器。这种新型器件基于短弹道二极管，其中电流是由于负有效质量（NEM）的载流子产生的，最初是由Wayne State小组在过去三年中提出并进行了数值模拟的。预计这些二极管将在0.1-10太赫兹频率范围内产生电振荡（对应于从3mm到30um的自由空间波长）。与其他固态太赫兹发生器相比，这些装置的运行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，辐射频率是可调的电压施加到二极管。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：p型调制掺杂GaAs量子阱与量子化NEM孔中制造和表征短基弹道二极管。高迁移率的二维空穴气体将在布朗大学和普林斯顿大学（Mansour Shayegan的团队已经在那里获得了高质量的空穴气体）生长。在项目的后期阶段，当需要进行高频测量时，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生成理论。一种提议的装置涉及通过发射极异质结注入NEM电流载流子，而不是在自一致的电场中加速。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脱钩，从而使产生的辐射的频率上限显著提高。其他提出的器件将产生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。虽然制造起来比较困难，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.***