Investigation of c-plane, Ga-face GaN surface band bending toward bipolar transistor application
Abstract
Heterojunctions bipolar transistors (HBT), if can be realized with GaN, have inherent advantages in current density and therefore power handling capability compared to the counterpart of GaN HEMTs due to its vertical current conducing configuration. However the inefficient p-type doping in nitrides hampers the realization of a GaN-based HBT. The PI invented an ultrathin-oxide (UO)-interface based lattice-mismatched heterostructure to overcome the technical barrier of epitaxial film growth of one material on top of another material with a different lattice constant and/or lattice structure. Using this lattice-mismatched heterostructure approach, the high density of interface defects encountered in the direct bonding or fusion of two materials has been alleviated, therefore, the potential to realize bipolar junction transistors using Ga-face n-type GaN as the collector of HBT has been revealed. The PI has already demonstrated epitaxy-like Ge/GaN, Si/GaN and GaAs/GaN p-n junctions with very low interface trap densities that are reflected on their record low reverse-bias current density, abrupt avalanche breakdown behavior, record low ideality factors, and record high rectifying ratio. As the PI further attempted to fabricate c-plane GaN-collector bipolar transistors, the AlGaAs/GaAs/GaN n-p-n HBT did not work as expected due to the polarization induced band up-bending and resultant energy barrier at the base-collector (B-C) junction.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jan 21, 2022
- Source ID
- FA95502110081XX0
Entities
People
- Zhenqiang Ma
Organizations
- Air Force Office of Scientific Research
- United States Air Force
- University of Wisconsin System