Transferred-Electron Induced Current Instabilities in Heterojunction Bipolar Transistors

半导体中电流的不稳定性已经引起了人们的兴趣。 一个众所周知的例子是技术上重要的古恩效应，该效应已在磷化铟和砷化镓等直接带隙半导体中观察到，其中偏置n+-n-n+二极管的电场分布塌陷到高场域中。 该区域在特征时间t内从n区域扫出，并产生频率f=1/t的电流脉冲。 自1963年古恩首次观察到转移电子效应以来，这种器件已成功地实现了微波和毫米波辐射的低噪声源。 III-V族异质结双极晶体管（HBT）的集电极区和古恩二极管的漂移区之间的相似性促使我们探索双极晶体管中的耿-希尔森现象。 使用数值模拟，我们已经表明，从转移的电子效应导致的电流不稳定性，可以观察到在修改后的HBT结构中，在集电极中的电场分布已被适当地设计。 这些结果建立了一个新的三端双极振荡器的设计标准，与现有的HBT集成电路技术，我们将在本项目中研究的潜力纳入。 所提出的设备将被用作一种新的光谱工具，其中它是可能的独立地改变电压和电流的稳定性发生在半导体的区域。 利用这一性质，我们可以应用广泛的偏置条件来评估的适用性的Landau-Ginzburg相变理论来描述波动附近的振荡阈值。 ***

9422538 Jalali Instabilities in current flow in semiconductors has been of interest of some time. A well known example is the technologically important Gunn effect which has been observed in direct bandgap semiconductors such as InP and GaAs in which the electric field profile of a biased n+-n-n+ diode collapses into a high field domain. This domain is swept out of the n-region in a characteristic time, t and results in current pulses of frequency f=1/t. Since the first observation of the transferred electron effect by Gunn in 1963 the devices have been successfully implemented as low noise source of microwave and millimeter-wave radiation. The similarity between the collector region of a III-V heterojunction bipolar transistor (HBT) and the drift region of a Gunn diode has motivated us to explore the Gunn-Hilsum phenomenon in bipolar transistors. Using numerical simulations, we have shown that current instabilities resulting from the transferred electron effect can be observed in modified HBT structures in which the electric field profile in the collector has been properly engineered. These results have established design criteria for a new three terminal bipolar oscillator with the potential for incorporation into existing HBT integrated circuit technology, which we shall study in the this project. The proposed device will be used as a novel spectroscopic tool in which it is possible to independently vary voltage and current flow in the region of semiconductor where stability occurs. Using this property we can apply a wide range of bias conditions to assess the applicability of the Landau-Ginzburg theory of phase transitions to describe fluctuations near oscillation threshold. ***