AVS 46th International Symposium
    Electronic Materials and Processing Division Monday Sessions
       Session EM-MoM

Paper EM-MoM8
Dissociation of Al@sub 2@O@sub 3@(0001) Substrates, and the Roles of Silicon, Oxygen, and Nitrogen Vacancies in n-type GaN Grown by MBE

Monday, October 25, 1999, 10:40 am, Room 608

Session: Nitride Epitaxy
Presenter: J.E. Van Nostrand, Air Force Research Lab
Authors: J.E. Van Nostrand, Air Force Research Lab
J.S. Solomon, University of Dayton Research Institute
A. Saxler, Air Force Research Lab
Correspondent: Click to Email
GaN is a semiconductor material that shows great promise for use in optoelectronic and electronic devices due to its large, direct bandgap. However, in spite of astonishing and rapid developmental successes, many problems remain that hinder further progress. Among them is a lack of understanding of the mechanisms underlying impurity incorporation, the nature of native defects, and the dependence of both of these on the thermodynamics and kinetic limitations of the GaN growth technique employed. One nearly universal aspect of unintentionally doped GaN films grown on sapphire by any technique is an n-type background carrier concentration. This phenomenon has been attributed to impurities such as Si or O, or to native defects such as N vacancies. In this work, we identify and quantify an anomalous relationship between the Si doping concentration and free carrier concentration and mobility using temperature dependent Hall measurements on a series of 2.0 µm thick GaN(0001) films grown on sapphire with various Si doping concentrations. Secondary ion mass spectrometry (SIMS) is used to identify the type of the excess free carriers to be oxygen. Further, the source of the oxygen is positively identified to be dissociation of the sapphire substrate at the sapphire-nitride interface. Finally, SIMS is again utilized to show how Si doping can be utilized to control the diffusion kinetics of the oxygen into the GaN layer from the sapphire substrate.