Development of High Breakdown Voltage InGaP/GaAs DHBTs

In this paper, we report the development of a high breakdown voltage InGaP/GaAs HBT process for low-to-mid power and high-voltage power amplifier operation. To achieve the high-breakdown InGaP HBT, two different collector designs and collector-etch processes were investigated. The first device process approach uses a thick GaAs collector with low n doping. The process challenges and considerations of this long collector approach are briefly discussed. An alternative approach uses wide band gap InGaP material as part of the collector design. High breakdown voltage can be obtained from both material design approaches. However, to fully leverage the existing process modules of our high volume HBT production line and allow the re-use of our current HBT design rules and libraries, our high voltage HBT (HV-HBT) development efforts focus on HBTs with InGaP in the collector (either composite collector, CCHBT, or double heterojunctions, DHBTs). Using a slightly modified process, InGaP DHBT devices have been demonstrated with BVceo and BVcbo values of 40 V and 56 V, respectively. A cut off frequency, ft, of 40 GHz has also been obtained at a current density of Jc=0.3 mA/μm by using this process. Preliminary circuit level performance results are also presented and discussed.