Carrier Physics at High Electric Fields in Wide and Ultra-Wide Bandgap Semiconductors
Abstract
The proposed program is focused on understanding the processes in high power, high electric field devices that are essential for DoD including wide bandgap and ultrawide bandgap rf, THz, and power devices. Often, the underlying structure and processes in semiconductors are inferred, based on computation or simulation, or indirectly measured - this is almost exclusively the case for high field transport, impact ionization, breakdown, and ultra-hot carrier relaxation. Correct understanding of hot carrier physics requires knowledge of the conduction band dispersion E(k) throughout the Brillouin Zone (BZ) to energies at least ~1.5× the bandgap, Eg, of the semiconductor and the carrier distribution in phase space in devices. The proposed program will be focused on developing the methods of angle resolved electron emission spectroscopy (AR-EES) to experimentally determine the conduction band dispersion (band structure) E(k) on wide bandgap and ultra-wide bandgap semiconductors. In the case of GaN, correct experimental determination of E(k) will yield the energy and k-position of the satellite valleys. In situ AR-EES studies on high field devices will determine the carrier distribution. These experiments will address basic questions including the sequence of processes for carriers to gain energy in high fields. The experiments will provide key input for electronic structure calculations and Monte Carlo simulations. The program will focus on GaN-based materials. The test structures will be designed in collaboration between UCSB (PI Speck), AFRL (PI Back) and NTU (PI Wu). The EES test structures will be grown and processed at UCSB, and the main measurements will be made at AFRL. The experimentally determined E(k) will be incorporated in Monte Carlo simulations by PI Wu and the results compared with carrier distributions measured by AR-EES for high field experiments.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Feb 05, 2025
- Source ID
- FA23862414050
Entities
People
- James S. Speck
Organizations
- Air Force Office of Scientific Research
- United States Air Force
- University of California, Santa Barbara