Effects of collector doping on DC and RF performance of AlInAs/GaInAs/InP double heterojunction bipolar transistors

AlInAs/GaInAs/InP double heterojunction bipolar transistors (DHBTs) with three different InP collector dopings of 1.4*10/sup 16/, 2.4*10/sup 16/, and 3*10/sup 16/ cm/sup -3/ and a collector thickness of 0.75 mu m have been made for microwave power applications. The DC and RF performance of the devices was found to be strongly dependent on the collector doping. This strong sensitivity to the collector doping is due to the conduction band discontinuity between GaInAs and InP at the base-collector junction. DC and RF characterization was performed on 2- mu m*20- mu m single-emitter geometry devices which are used in the construction of the microwave power cells. The DHBTs achieved base-collector breakdown voltages in excess of 20 V and common-emitter breakdown voltages of more than 14 V (both measured at 100 mu A of current). The f/sub T/ and f/sub max/ of the devices were in the range of 65 to 75 GHz. DC current gains were in the range of 50 to 70. The devices with the collector doping of 3*10/sup 16/ cm/sup -3/ could be operated up to 10/sup 5/ A/cm/sup 2/ collector current density without gain compression.