Abstract
We review the surface stability and growth kinetics of III-V and III-nitride semiconductors. The theoretical approach used in these studies is based on ab initio calculations and includes gas-phase free energy. With this method, we can investigate the influence of growth conditions, such as partial pressure and temperature, on the surface stability and growth kinetics. First, we examine the feasibility of this approach by comparing calculated surface phase diagrams of GaAs(001) with experimental results. In addition, the Ga diffusion length on GaAs(001) during molecular beam epitaxy is discussed. Next, this approach is systematically applied to the reconstruction, adsorption and incorporation on various nitride semiconductor surfaces. The calculated results for nitride semiconductor surface reconstructions with polar, nonpolar, and semipolar orientations suggest that adlayer reconstructions generally appear on the polar and the semipolar surfaces. However, the stable ideal surface without adsorption is found on the nonpolar surfaces because the ideal surface satisfies the electron counting rule. Finally, the stability of hydrogen and the incorporation mechanisms of Mg and C during metalorganic vapor phase epitaxy are discussed.
Highlights
The GaN 1122 surface phase diagram presented in Figure 27f indicates that the stable region of the N–H + Ga–NH + Ga–NH2 expands over the wide temperature and Ga beam equivalent pressure (BEP) range, suggesting that this structure always emerges at temperatures ranging from 1200 to 1400 K regardless of Ga pressure [45,47]
We compared the theoretical and experimental Ga diffusion lengths on the GaAs(001)-(2 × 4)β2 surface, which showed good agreement. This suggests that the ab initio-based approach is a powerful tool for investigating the surface stability and growth kinetics in the vapor phase epitaxy (VPE) of compound semiconductors
The calculated results for surface reconstructions with polar, nonpolar, and semipolar orientations suggest that the reconstructions on nitride surfaces with adlayers appear on the polar and semipolar surfaces
Summary
Current semiconductor devices, such as optical and electronic devices, are fabricated using the vapor phase epitaxy (VPE) technique whereby a gas-solid interface is formed at the growth front. Qian et al [3] discussed the relationship between the stoichiometry and the surface reconstruction on GaAs(001) using chemical potentials. Northrup [4] classified the stable structures on Si(001)H using the chemical potential of H All of these approaches discussed the static structural surface stability at 0 K, even though their methodologies were different. The theoretical approach is useful for analyzing the influence of temperature and pressure on the stability of the reconstructed surfaces. By applying this method, growth kinetics and processes can be investigated. We discuss reconstructed structure stabilities and elementary growth processes on GaAs and III-nitride surfaces during MBE and MBE/MOVPE processes, respectively
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