High temperature and low pressure chemical vapor deposition of silicon nitride on AlGaN: Band offsets and passivation studies
Abstract
In this work, we employed X-ray photoelectron spectroscopy to determine the band offsets and interface Fermi level at the heterojunction formed by stoichiometric silicon nitride deposited on AlxGa1-xN (of varying Al composition “x”) via low pressure chemical vapor deposition. Silicon nitride is found to form a type II staggered band alignment with AlGaN for all Al compositions (0 ≤ x ≤ 1) and present an electron barrier into AlGaN even at higher Al compositions, where Eg(AlGaN) > Eg(Si3N4). Further, no band bending is observed in AlGaN for x ≤ 0.6 and a reduced band bending (by ∼1 eV in comparison to that at free surface) is observed for x > 0.6. The Fermi level in silicon nitride is found to be at 3 eV with respect to its valence band, which is likely due to silicon (≡Si0/−1) dangling bonds. The presence of band bending for x > 0.6 is seen as a likely consequence of Fermi level alignment at Si3N4/AlGaN hetero-interface and not due to interface states. Photoelectron spectroscopy results are corroborated by current-voltage-temperature and capacitance-voltage measurements. A shift in the interface Fermi level (before band bending at equilibrium) from the conduction band in Si3N4/n-GaN to the valence band in Si3N4/p-GaN is observed, which strongly indicates a reduction in mid-gap interface states. Hence, stoichiometric silicon nitride is found to be a feasible passivation and dielectric insulation material for AlGaN at any composition.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Apr 11, 2016
- Source ID
- 10.1063/1.4945775
Entities
People
- Alexander Franke
- Biplab Sarkar
- Brian B. Haidet
- Dorian Alden
- Erhard Kohn
- Felix Kaess
- Luis H. Hernandez-balderrama
- M. Hayden Breckenridge
- Pramod Reddy
- Ramón Collazo
- Shun Washiyama
- Zlatko Sitar
Organizations
- Army Research Office
- National Science Foundation
- North Carolina State University
- Wofford College