I. Introduction
Bipolar transistor structures for BiCMOS integration are usually based on the super-self-aligned transistor [1]. Different values of breakdown voltages are obtained by controlling the intrinsic collector concentration through various parameters of the selectively implanted collector, which usually requires additional lithography masks and increases the cost of technology. On the other hand, high-voltage bipolar transistors such as reduced surface field devices [2], gate associated transistor [3], and trench base-shielded bipolar transistor [4] take advantage of transistor geometry to achieve a high breakdown voltage. In these devices, the collector is fully depleted in the forward active mode of operation. This way, the maximum value of the electric field at the intrinsic base–collector junction is reduced, and the intrinsic base is shielded from the collector voltage. A similar effect of the limited electric field at the intrinsic base–collector junction is observed in vertical-current SiGe bipolar junction transistors made on a thin silicon-on-insulator (SOI) [5], [6], where collector charge is limited by the SOI thickness, and potential is pinned at the interface when the collector is fully depleted.