The almost periodic streaming motion of accelerated electrons under moderate electric fields coupled with almost periodic emission of longitudinal optical (LO) phonons is studied in a gallium nitride quantum-well—a promising pathway for terahertz (THz) oscillations. The optimal conditions for the LO-phonon-terminated streaming depend, among others, on the density of the electron gas, the low-field electron mobility, the lattice temperature, and the electric field in a very specific way. The present manuscript exploited the electron noise temperature measured at an X band frequency as a marker for the oscillations at THz frequencies. The idea was tested on a deterministic model for a GaN two-dimensional electron gas (2DEG) through calculation of the electron noise temperature spectra in the Langevin approach for the frequency range from 1 GHz to 10 THz. The noise temperature at 10 GHz was found to be in a strong anticorrelation with the THz peaks in the noise temperature spectrum. In particular, a weaker dependence on the applied electric field at 10 GHz implies stronger THz oscillations. In an experiment, the microwave hot-electron noise measurements were carried out for AlGaN/AlN/GaN heterostructures with the 2DEG channel at 10 GHz under pulsed electric field conditions in order to mitigate the effect of Joule heating of the channel. The plateau-like behavior of the noise temperature, in its dependence on the electric field, was obtained for the 2DEG channels with rather low electron densities ($2.5\times {10}^{12}$ cm${}^{-2}$) in a good agreement with the model. The aforementioned plateau in the electron noise temperature observed at 10 GHz can be used as an indicator for the THz oscillations.

中文翻译：

---

微波频率下热电子噪声温度行为预测氮化镓量子阱通道中的太赫兹振荡

在氮化镓量子阱中研究了在中等电场下加速电子的几乎周期性的流运动，以及纵向光学（LO）声子的几乎周期性的发射，这是太赫兹（THz）振荡的有希望的途径。LO-声子封端的流的最佳条件尤其取决于电子气的密度，低场电子迁移率，晶格温度和电场。本手稿利用在X波段频率下测得的电子噪声温度作为THz频率下振荡的标志。通过在Langevin方法中计算1 GHz至10 THz频率范围内的电子噪声温度谱，在GaN二维电子气（2DEG）的确定性模型上对该想法进行了测试。发现10 GHz的噪声温度与噪声温度谱中的THz峰值具有很强的反相关性。特别是，对10 GHz时施加的电场的依赖性越弱，则意味着THz振荡越强。在实验中，为了在10 GHz下在脉冲电场条件下对带有2DEG沟道的AlGaN / AlN / GaN异质结构进行微波热电子噪声测量，以减轻沟道的焦耳热效应。噪声温度的平稳状态取决于电场，$2.5\times {10}^{12}$ 厘米${}^{-2}$）与模型保持良好的一致性。在10 GHz处观察到的电子噪声温度的上述平稳期可以用作THz振荡的指标。