Current Instability and Gunn Effect in Two-Dimensional Systems

0080509 Shur本项目的目的是研究短沟道场效应晶体管中的非线性输运现象。 最近Dyakonov和Shur发现二维通道中的电子流体流动是不稳定的。 这种不稳定性导致在太赫兹频率范围内产生等离子体波。 在此基础上，提出了新型太赫兹器件（振荡器、探测器、混频器），并成功研制了太赫兹场效应管探测器。 将研究由不稳定性发展引起的定常非线性振荡。 不稳定性引起的冲击波的形状、振幅和速度将在考虑电子-电子散射引起的电子流体的粘度以及与声子和杂质散射相关的外部摩擦的情况下计算。 将分析结果与数值计算结果进行了比较。 该理论还将描述基于短沟道场效应晶体管的太赫兹辐射探测器的非线性操作机制。 这种不稳定性也将在小的电子密度的情况下，当电子-电子碰撞可以忽略不计（碰撞等离子体）进行研究。 我们将找到无碰撞等离子体不稳定性的条件，并考虑不稳定性的线性区。 计算振荡的共振频率和不稳定性的增量。他们研究的另一个主题是二维系统中所谓的“失控”效应，这种效应导致负微分电阻。 他们的初步估计表明，在三维的情况下，这样的失控发生，即使变形光学和声学声子散射。 它应该导致基于硅（锗）的2D系统中的负微分迁移率。 本计画的主要任务之一是探讨二维矽（锗）金氧半结构中产生古恩效应的可能性。 将研究二维FET沟道中的负微分的后果。 这种情况应该与传统的三维古恩效应有很大的不同，因为扩散非指数定律控制着二维FET沟道中的电荷弛豫。 还将研究电子-电子相互作用对2D“逃逸”的作用。

0080509ShurThe purpose of the proposed project is to study the non-linear transport phenomena in short - channel Field Effect Transistors. Recently Dyakonov and Shur have discovered that flow of the electron fluid in two-dimensional channel should be unstable. This instability results in plasma wave generation in a terahertz frequency range. As a consequence, the novel terahertz devices (oscillator, detector, mixer) were proposed, and a terahertz FET detector has been demonstrated.A strong non-linear regime of this instability in a ballistic field effect transistor will be studied. The stationary non-linear oscillations resulting from development of the instability will be investigated. The shape, amplitude, and velocity of the shock waves caused by the instability will be calculated taking into account the viscosity of the electron fluid due to electron-electron scattering and the external friction related to the scattering by phonons and impurities. The analytical results will be compared with the numerical calculation. This theory will also describe a non-linear regime of operation of a terahertz radiation detector based on the short-channel field effect transistor. This instability will also be studied in the case of small electron densities when the electron-electron collisions can be neglected (collisionless plasma). The conditions of the instability for collisionless plasma will be found. The linear regime of the instability will be also considered. The resonant frequencies of oscillations and the increment of instability will be calculated.Another topic of their study is a so-called "runaway" effect in two-dimensional systems, which leads to the negative differential resistance. Their preliminary estimates show that, in contrast to a three dimensional case, such runaway takes place even for deformation optical and acoustic phonon scattering. It should lead to a negative differential mobility in 2D systems based on silicon (germanium). One of the main tasks of the project is to investigate a possibility of the Gunn generation in 2D Si (Ge) MOS structures. The consequences of the negative differential in the two-dimensional FET channel will be studied. This case should differ substantially from the conventional three-dimensional Gunn effect since diffusion non-exponential law governs the charge relaxation in two-dimensional FET channel. The role of electron-electron interactions for 2D "runaway" will also be investigated.