Review of Structure of Bare and Adsorbate-Covered GaN(0001) Surfaces
- PDF / 1,850,898 Bytes
- 27 Pages / 612 x 792 pts (letter) Page_size
- 53 Downloads / 162 Views
Internet Journal Nitride Semiconductor Research
Review of Structure of Bare and Adsorbate-Covered GaN(0001) Surfaces R. M. Feenstra1, J. E. Northrup2 and Jörg Neugebauer3 1Department
of Physics, Carnegie Mellon University, Research Center, 3Fritz-Haber-Institut der MPG, 2Palo Alto
(Received Friday, March 22, 2002; accepted Wednesday, May 1, 2002)
A review of surface structures of bare and adsorbate-covered GaN (0001) and (0001) surfaces is presented, including results for In, Mg, Si, and H adsorbates. Emphasis is given to direct determination of surface structure employing experimental techniques such as scanning tunneling microscopy, electron diffraction, and Auger electron spectroscopy, and utilizing first principles computations of the total energy of various structural models. Different surface stoichiometries are studied experimentally by varying the surface preparation conditions (e.g. Ga-rich compared to Nrich), and the stoichiometry is included in the theory by performing calculations for various chemical potentials of the constituent atoms. Based on the work reviewed here, surface reconstructions for plasma-assisted molecular beam epitaxy growth of GaN (0001) and (0001) surfaces are fairly well understood, but reconstructions for reactive molecular beam epitaxy or for metal-organic vapor phase epitaxy (both involving H, at moderate and high temperatures, respectively) are less well understood at present.
1
Introduction
Gallium nitride and other III-nitrides have attracted considerable interest recently because of their applications for blue light-emitting diodes and lasers and for high frequency/high power transistors [1] [2] [3] [4] [5] [6] [7]. These materials have several unique properties compared to the more conventional III-V semiconductors (GaAs, InP, etc.): they exist in both cubic (zincblende) and hexagonal (wurtzite) form, they are refractory, and some of the materials have large band gaps. The relatively small size of nitrogen, compared to Ga or In, in these compounds leads to a number of unique surface structures, which have been explored in several papers for the (001) growth surface of cubic GaN [8] [9] [10]. For the technologically more relevant (0001) growth surface of hexagonal GaN, reports over the past 5 years have led to considerable understanding of its structure, for both bare and adsorbate covered surfaces. This article presents a review of these studies of the surface science of wurtzite GaN (0001) and (0001) surfaces. It is important to understand the surface structures of these materials, since this knowledge will impact our ability to achieve high quality epitaxial growth of the materials
as required for optoelectronic and electronic applications. Common growth methods for GaN films include metal-organic vapor phase epitaxy (MOVPE) and molecular beam epitaxy (MBE). The latter can be performed using a plasma source for nitrogen (plasmaassisted MBE, or PAMBE) or using ammonia, which thermally decomposes on the growth surface (reactive MBE, or RMBE). The MBE technique by vir
Data Loading...
