A new adjustable insulated gate bipolar transistor (IGBT) with Si/SiGe heterojunction collector structures is proposed to improve the operation speed and decrease the turnoff power loss by suppressing the tail-current. SiGe collector provides low contact resistance without consequently sacrificing turnoff losses, and also acts to suppress hole-injection into drift region during on-state and accelerate the clear sweep of the holes when the device is cutoff. On the other hand, turn-on voltage loss is increased due to the use of SiGe collector. This drawback can be minimized by using lower percentages of Ge in SiGe, since the potential barrier height at the Si/SiGe junction is controlled by the percentage of Ge in SiGe, which means the proposed IGBT can be tuned freely to meet different needs by means of changing the percentage of Ge region in the SiGe. Further, the proposed IGBT exhibits a more superior on-state/switching tradeoff relation when compared to the conventional IGBT. Two-dimensional device and circuit mixed-mode simulations are also performed to offer valuable information about the internal dynamical mechanisms of these devices, thus improving the understanding of device performance in SiGe collector applications