Simulation of High Speed Pseudomorphic Heterojunction Bipolar Transistors

一个特定的目标是将晶格匹配异质结半导体器件的数值模拟技术扩展到应变层（伪晶）异质结半导体器件，用于高速和/或高速频率的应用程序。在过去的三年中，我们已经对A1GaAs/GaAs和InGaAs/ ina1ashbt进行了建模。利用有限差分漂移扩散方程（DDE）求解器和数值小信号交流分析，模拟了这些器件的终端特性以及fT和fmax。鉴于最近对应变层半导体的兴趣，将我们目前的研究扩展到涉及应变层的HBTs的建模是很自然的。重点将放在Si -x Gex/Si和InxGa1-x As/GaAs系统上。要建模的基本异质结结构是具有应变双异质结的垂直器件，具有发射端或集电极端结构。蒙特卡罗方法将用于确定材料的基本性质，如迁移率，不同的耦合常数需要正确建模非平稳效应，如超调，并对怀疑发生这些效应的选定区域进行全面的区域分析，例如在HBT的碱基集电极区域。在下一步中，将使用从玻尔兹曼输运方程的前三个矩获得的流体动力学方程和从MC数据导出的输运系数进行计算。这些计算的结果将使我们能够计算稳态直流和小信号交流参数，范围从电流增益到fT和fmax。模拟结果将与公布的数据或与IBM公司的研究人员合作进行的实际设备测量进行比较。希望本研究能为当今发达的硅技术带来异质结的优势GaAs技术在最快半导体器件的竞赛中又向前迈进了一步。

A specific objective is to extend the state-of-the-art of the numerical modeling of lattice-matched heterojunction semiconductor devices to strained-layer (pseudomorphic) heterojunction semiconductor devices for high speed and/or high frequency applications. Over the last three years, we have modeled A1GaAs/GaAs and InGaAs/InA1AsHBTs. Using a finite difference drift-diffusion equations (DDE) solver and numerical small-signal a.c. analysis, terminal characteristics as well as fT and fmax of these devices have been simulated. In view of recent interest in strained-layer semiconductors, it is natural to extend our current research to the modeling of HBTs involving strained layers. Focus will be placed on Si1-x Gex/Si and InxGa1-x As/GaAs systems. The basic heterojunction structures to be modeled are vertical devices having strained double heterojunctions with either emitter-top or collector-top configurations. The Monte Carlo method will be used to determine fundamental material properties, e.g. mobility, different coupling constants needed for proper modeling of non- stationary effects such as overshoot, and to perform full regional analysis of selected regions where these effects are suspected to be taking place, e.g. in the base-collector region of an HBT. In the next step, calculations will be performed using hydrodynamic equations obtained from the first three moments of the Boltzmann transport equation with the transport coefficients derived form the MC data. The results of these calculations will enable us to calculate both steady state d.c. and small-signal a.c. parameters, ranging from current gain to fT and fmax. Simulation results will be compared with either published data or with actual device measurements to be carried out in collaboration with researchers of the IBM Corporation. It is hoped that this research will bring heterojunctions advantages to today's well developed silicon technology and also take GaAs technology one step further in the race for the fastest semiconductor device.