Novel Strained Si/SiGe HBT for High Product of Current Gain and Breakdown Voltage

To improve the high voltage and high current handling capability,a model of strained Si/SiGe HBT is established with SILVACO TCAD to study the influence of the virtual substrate on current gain of the device.Higher Ge composition of the base can be achieved with the virtual substrate while keeping the strain between the base and the collector constant,and hence the current gain is enhanced.However,the breakdown voltage is too low to increase the output power and signal-to-noise ratio of the system.A new design of selectively implanted collector in device with virtual substrate is proposed considering that collector design is associated with the breakdown voltage while irrelevant of the current gain.A lateral electric field is built up with the design,and thereby the breakdown voltage is enhanced.Resultsshow that for the novel device,both the current gain and the breakdown voltage are markedly improved and the figure of merit β ? V_CEO is 14.2 times as much as that of the traditional SiGe HBT,which effectively develops the high voltage and high current application of microwave power SiGe HBT.