Development of gallium nitride-based PNP heterojunction bipolar transistors.
- Resource Type
- Theses
- Authors
- Green, Daniel S.
- Source
- Dissertation Abstracts International; Dissertation Abstract International; 67-05B.
- Subject
- Engineering, Electronics and Electrical
Engineering, Materials Science
- Language
- English
Summary: This work was designed to demonstrate and understand the pnp HBT. The research served as both an engineering challenge as well as an investigation of physical parameters governing the transport in the device. In order to remedy the poor collector contact available with buried p-GaN, a transformation diode HBT structure was introduced that added an n-type subcollector the HBT structure. This allowed for good collector contact at the cost of introducing an offset voltage to the HBT performance due to the turn-on voltage of the transformation diode under normal operation. The first transformation diode HBT in GaN was successful demonstrated. In order to improve the transformation diode performance, successive design iterations were performed to isolate the performance limiting elements. Device designs were implemented to mitigate saturated hole velocity, as well as to decrease base transit time through aggressive base scaling and compositional grading. Physical simulations and modelling of device non-idealities were used to understand actual device performance. Hole lifetime and saturated hole velocity were identified as primary contributors to lower than expected performance device performance. Successive device iterations yielded HBT performance of beta ∼ 2 for a current density of ∼ 50 A cm-2.