AVS 51st International Symposium
    Science of Semiconductor White Light Topical Conference Wednesday Sessions
       Session WL+MS-WeA

Invited Paper WL+MS-WeA7
Passivation and Processing-Induced Changes in GaN/Insulator Interfaces

Wednesday, November 17, 2004, 4:00 pm, Room 304B

Session: Science of Semiconductor White Light II
Presenter: R.J. Nemanich, NC State University
Authors: R.J. Nemanich, NC State University
T.E. Cook, Jr., NC State University
C.C. Fulton, NC State University
W.J. Mecouch, NC State University
R.F. Davis, NC State University
G. Lucovsky, NC State University
Correspondent: Click to Email
Passivation of GaN and AlGaN surfaces is now a critical limitation in electronic device fabrication. The band relations of various dielectrics on III-nitrides are just being established, and some interfaces show significant process induced variations. The characteristics of clean n- and p-type GaN (0001) surfaces and the interface between this surface and SiO2, Si3N4, and HfO2 have been investigated. Layers of SiO2, Si3N4, or HfO2 were carefully deposited to limit the reaction between the dielectric and the clean GaN surfaces. After stepwise deposition, the electronic states were measured with x-ray photoelectron spectroscopy (XPS) and ultraviolet photoemission spectroscopy (UPS). A valence band offset (VBO) of 2.0 eV with a conduction band offset (CBO) of 3.6 eV was determined for the GaN/SiO2 interface. For the GaN/Si3N4 interface, type II band alignment was observed with a VBO of 0.5 eV with a CBO of 2.4 eV, which differs substantially from prior reports. We suggest that the differences are related to the level of oxygen incorporated at the interface. A VBO of 0.4 eV with a CBO of 2.0 eV was determined for the GaN/HfO2 interface. An instability was observed in the HfO2 film, with energy bands shifting ~0.5 eV during a 650°C densification anneal. The deduced band alignments were compared to the predictions of the electron affinity model and deviations were attributed to a change of the interface dipole. The largest deviation was observed for the oxide layers. It was noted that the existence of Ga-O bonding at the heterojunction can significantly affect the interface dipole, and consequently the band alignment in relation to the GaN.