Collector optimization for tradeoff between breakdown voltage and cut-off frequency in SiGe HBT

As is well known, there exists a tradeoff between the breakdown voltage BVCEOand the cut-off frequency fTfor a standard heterojunction bipolar transistor(HBT). In this paper, this tradeoff is alleviated by collector doping engineering in the SiGe HBT by utilizing a novel composite of P+and N-doping layers inside the collector–base(CB) space-charge region(SCR). Compared with the single N-type collector, the introduction of the thin P+layers provides a reverse electric field weakening the electric field near the CB metallurgical junction without changing the field direction, and the thin Nlayer further effectively lowers the electric field near the CB metallurgical junction. As a result, the electron temperature near the CB metallurgical junction is lowered, consequently suppressing the impact ionization, thus BVCEOis improved with a slight degradation in fT. The results show that the product of fT×BVCEOis improved from 309.51 GHz·V to326.35 GHz·V.     

采用发射极非均匀指间距技术改善功率异质结双极晶体管热稳定性的研究

为了提高多发射极功率异质结双极晶体管的热稳定性,本文利用耦合热阻表征发射极指间距变化对发射极指间热耦合作用的影响,得到了耦合热阻与发射极指间距之间的变化关系,提出了发射极非均匀指间距技术.通过热电反馈模型对采用发射极非均匀指间距技术的功率HBT进行热稳定性分析,得到了多发射极指上的温度分布.结果表明,多发射极HBT在采用非均匀发射极指间距技术后,峰值温度明显下降,温度变化幅度更加平缓,有效地提高了器件的热稳定性. 关键词： 异质结双极晶体管 耦合热阻 指间距     

Thermal stability improvement of a multiple finger power SiGe heterojunction bipolar transistor under different power dissipations using non-uniform finger spacing

A method of non-uniform finger spacing is proposed to enhance thermal stability of a multiple finger power SiGe heterojunction bipolar transistor under different power dissipations. Temperature distribution on the emitter fingers of a multi-finger SiGe heterojunction bipolar transistor is studied using a numerical electro-thermal model. The results show that the SiGe heterojunction bipolar transistor with non-uniform finger spacing has a small temperature difference between fingers compared with a traditional uniform finger spacing heterojunction bipolar transistor at the same power dissipation. What is most important is that the ability to improve temperature non-uniformity is not weakened as power dissipation increases. So the method of non-uniform finger spacing is very effective in enhancing the thermal stability and the power handing capability of power device. Experimental results verify our conclusions.