Bandwidth Enhancement in an Integratable SiGe Phototransistor by Removal of Excess Carriers

In this letter, we create a path to remove excess carriers in the base region of a SiGe phototransistor (HPT) by introducing the trap centers. The behavior of the trap centers in the SiGe heterojunction bipolar transistor (HBT) is a form of nonideal (nkT) base current. The responsivity of the device is /spl sim/0.43 A/W with fully SiGe HBT-compatible device structure to facilitate the integration of the following amplification circuitry. The full-width at half-maximum of the pulse is /spl sim/90 ps and the tail of the optical pulse response is largely reduced with the nkT current. By reducing the tail, bandwidth is increased from 1.5 to 3 GHz. This proposes SiGe HPT is applicable for optoelectronic technology.