Design of a novel strained-SI HBT with virtual substrate for high current gain-breakdown voltage product
In order to weaken the lattice self-heating effect of strained-Si HBT with vertical substrate, a trapezoid Ge doping profile in base is proposed and the device model is established with SILVACO TCAD. It is shown that temperature coefficient of the device is decreased, which is benefit for high power application, at the expense of the decrease of the current gain. Therefore, a further design of superjunction collector structure is presented to enhance the breakdown voltage which is irrelevant to the current gain. As a result, the product of current gain-breakdown voltage in the novel strained-Si HBT with vertical substrate is 1.61 times higher that the conventional device, which develops the high power application of SiGe HBTs.