Performance improvement of SiGe-HBT terahertz detectors using exponential base grading

Nowadays Terahertz Electronics and optoelectronic devices and systems play important roles in many researches in various fields of science, technology and medicine. In this paper a new modified version of a SiGe-HBT which is used in a pre-implemented direct conversion terahertz detector has been proposed for improving technical characteristics of detector device. Benefits of our new proposed device is because of introducing an exponential Germanium grading profile in base region of SiGe-HBT in order to improve base transit time which can effectively boost high frequency performance of transistor. For confirmation of our analysis we use Continuity and Poisson's equations to obtain better performance for our new proposed transistor. TCAD SILVACO software have been used for simulations. Our results and previously reported empirical results are compared. Comparison takes place for both of prefabricated and our new proposed device. Based on simulation analysis, responsivity of our detector is improved about 17% from 1 A/W to 1.17 A/W and its bandwidth is also improved about 80 GHz. Power consumption and noise performance of the new device are also considerably improved in comparison with the initial detector design.