AVS 50th International Symposium
    Semiconductors Monday Sessions
       Session SC-MoM

Paper SC-MoM7
Optical Studies on the Incorporation of Carbon as a Dopant in Cubic GaN

Monday, November 3, 2003, 10:20 am, Room 321/322

Session: Heteroepitaxy of Wide Bandgap Semiconductors
Presenter: J.A.N.T. Soares, Universidade de São Paulo, Brazil
Authors: J.A.N.T. Soares, Universidade de São Paulo, Brazil
J.R.L. Fernandez, Universidade Estadual de Campinas, Brazil
F. Cerdeira, Universidade Estadual de Campinas, Brazil
E.A. Meneses, Universidade Estadual de Campinas, Brazil
M.J.S.P. Brasil, Universidade Estadual de Campinas, Brazil
A.M. Santos, Universidade de São Paulo, Brazil
O.C. Noriega, Universidade de São Paulo, Brazil
J.R. Leite, Universidade de São Paulo, Brazil
D.J. As, Universität Paderborn, Germany
U. Köhler, Universität Paderborn, Germany
S. Potthast, Universität Paderborn, Germany
D.G. Pacheco-Salazar, Universität Paderborn, Germany
Correspondent: Click to Email
The metastable cubic phase of GaN (c-GaN) has attracted a lot of attention for its potential optoelectronic applications, especially since the successful fabrication of light-emitting diodes based on this material. In contrast to the wurtzite variety, no spontaneous polarization or strain-induced piezoelectric field exists in the cubic polytype grown on (001) planes. Hence, a greater optical recombination efficiency in c-GaN is expected, due to a greater overlap between electrons and holes wave functions. For the fabrication of devices it is essential to be able to introduce p- and n-type doping in a controlled manner. Among the possible acceptor impurities, carbon (C) has been regarded as an interesting candidate due to its similarity with nitrogen, both in atomic radius and electronegativity. Recently, D.J.As@footnote 1@ reported p-type doping with C during c-GaN plasma-assisted molecular beam epitaxy (PA-MBE) achieving concentrations of the order of 3x10@super 20@cm@super -3@. In order to render this impurity concentration into a high concentration of mobile holes, the details of C incorporation in the GaN lattice must be understood. In this work we performed Raman, photoluminescence, photoluminescence excitation, and photoreflectance spectroscopies on C doped c-GaN samples, deposited by PA-MBE on (001) GaAs substrates, for various C concentrations. The evolution of all four types of spectra is consistent with C atoms initially entering into N-vacancies producing a marked improvement in the crystalline properties of the material. At higher concentrations they also begin to enter interstitially and form C complexes, with a consequent decrease of crystalline quality. A model calculation of the localized vibrations of the C-atom in the GaN lattice allows for the interpretation of a feature in the Raman spectrum of samples with an "optimum" C concentration, which reinforces this view. @FootnoteText@@footnote 1@D.J.As et al., J.Phys.:Condens.Matter 13, 8923 (2001).