SiGe HBT直流特性模型研究

Study of DC characteristics models of SiGe HBT

在求解漂移扩散方程的基础上,建立了全面系统的SiGeHBT直流特性模型及物理意义清晰的各电流解析表达式.所建立的SiGeHBT直流特性的各电流模型均适应大注入及小注入情况.模拟分析了基区掺杂浓度及Ge组分对电流密度的影响,模拟结果表明,基区掺杂浓度的增加减小了集电极电流、增大了中性基区复合电流,从而降低了电流增益;而Ge组分越高,集电极电流密度就越大,从而提高了SiGeHBT的电流增益.模拟了基区发射结侧Ge组分及发射区掺杂浓度对基区空穴反注入电流密度的影响,结果表明,提高Ge组分能明显减小空穴反注入电流,获得更高的电流增益.

The SiGe HBT DC models and the analytic expressions for various currents with definite physical meanings are established based on the solution to equations of drift and diffusion. The established current models are suitable for both large and small current injections. MEDICI is used to simulate the effects of Ge content and doping concentration on current density. The simulating results show that the decrease of the current gain is due to the decrease of the collector current and the increase of the neutral base recombination current caused by the increase of base doping concentration. The effects of the collector current, backward hole injection current, neutral base recombination current and space-charge region recombination current on the current gain are also analyzed and discussed.