In order to improve the electrical and frequency characteristics of SiGe heterojunction bipolar transistors (HBTs), a novel structure of SOI SiGe heterojunction bipolar transistor is designed in this work. Compared with traditional SOI SiGe HBT, the proposed device structure has smaller window widths of emitter and collector areas. Under the act of additional uniaxial stress induced by Si 0.85 Ge 0.15 , all the collector region, base region and emitter region are strained, which is beneficial to improve the performance of SiGe HBTs. Employing the SILVACO  TCAD tools, the numerical simulation results show that the maximum current gain β max , the Earley voltage V A are achieved for 1062 and 186 V, respectively, the product of β and V A , i.e., β × V A , is 1.975 × 10 5 V and, the peak cutoff frequency f T is 419 GHz when the Ge component in the base has configured to be a trapezoidal distribution. The proposed SOI SiGe HBT architecture has a 52.9% improvement in cutoff frequency f T compared to the conventional SOI SiGe HBTs.

In order to further improve the performance of scaled silicon-germanium (SiGe) heterojunction bipolar transistor (HBT) and consider the compatibility with mature CMOS process, a novel SiGe HBT is designed by introducing the embedded Si1−yGey stress raiser into the collector. In the proposed HBT structure, the collector region is subjected to additional uniaxial stress, to enhance the characteristic frequency. The effect of embedded Si1−yGey stress raiser on the frequency performance with different Ge mole fractions is simulated and analyzed by employing SILVACO®TCAD tools. The simulation results show that the high frequency performance of the device can be significantly improved by applying additional uniaxial stress in the collector. At y = 0.3, the current gain of the device is increased by approximately 6% compared to the case where no stress is applied to the collector region (y = 0). Taking the uniform SiGe base case with the Ge fraction of 0.25 as an example, by adjusting the Ge fraction of the stress raiser, the peak values of fT and fmax reach about 507.7 GHz and 730.7 GHz, respectively. Compared with the traditional SiGe HBT without any additional stress in the collector region, fT and fmax are respectively increased by 29.1% and 71.5%. When y = 0.1, the proposed device has the best frequency characteristics due to the peak value of the fT ×fmax product.

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In order to further improve the performance of scaled silicon-germanium (SiGe) heterojunction bipolar transistor (HBT) and consider the compatibility with mature CMOS process, a novel SiGe HBT is designed by introducing the embedded Si1−yGey stress raiser into the collector. In the proposed HBT structure, the collector region is subjected to additional uniaxial stress, to enhance the characteristic frequency. The effect of embedded Si1−yGey stress raiser on the frequency performance with different Ge mole fractions is simulated and analyzed by employing SILVACO TCAD tools. The simulation results show that the high frequency performance of the device can be significantly improved by applying additional uniaxial stress in the collector. At y = 0.3, the current gain of the device is increased by approximately 6% compared to the case where no stress is applied to the collector region (y = 0). Taking the uniform SiGe base case with the Ge fraction of 0.25 as an example, by adjusting the Ge fraction of the stress raiser, the peak values of f T and f max reach about 507.7 GHz and 730.7 GHz, respectively. Compared with the traditional SiGe HBT without any additional stress in the collector region, f T and f max are respectively increased by 29.1% and 71.5%. When y = 0.1, the proposed device has the best frequency characteristics due to the peak value of the f T×f max product.