Identification of trap locations in AlGaN/GaN high electron mobility transistors by varying photon flux during sub-bandgap optical pumping
Abstract
By varying the photon flux during sub-bandgap optical pumping, the locations of traps associated with sub-bandgap laser pumping in AlGaN/GaN high electron mobility transistors (HEMTs) were identified. Fixed photon flux of sub-bandgap optical pumping was previously employed to determine the activation energies of traps in AlGaN/GaN HEMT; traps with activation energies of 0.73 eV, both 0.73 and 1.91 eV or all three trap states detected for the 671, 532, or 477 nm laser illumination, respectively. However, by illuminating the HEMTs with lower photon fluxes from 532 or 447 nm lasers, the traps with 0.73 eV were absent, and only the traps associated with higher activation energies were activated by the laser light. This indicated that the traps related to the activation energies of 1.91 and 2.35 eV are likely located at the surface of the HEMTs. Photon flux dependent gate-lag measurements were also conducted. Laser illumination of 671 nm did not affect the drain current during the gate lag measurement, implying the traps linked to the activation energy of 0.73 eV are not present in the AlGaN layer of the HEMT structure. On the other hand, the 1.91 and 2.35 eV trap states were distributed in the AlGaN layer of the HEMTs. This approach to selectively exciting the defect states provides a nondestructive method of probing the ionization levels and spatial location of traps in wide bandgap heterostructures.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Dec 02, 2015
- Source ID
- 10.1116/1.4936861
Entities
People
- Brent P. Gila
- David J. Cheney
- Fan Ren
- Shihyun Ahn
- Stephen Pearton
- Tsung Sheng Kang
- Yi-hsuan Lin
Organizations
- National Science Foundation
- United States Department of Defense
- University of Florida