DFT modeling of carbon incorporation in GaN(0001) and GaN(0001¯) metalorganic vapor phase epitaxy

Abstract

The carbon incorporation mechanism in GaN(0001) and GaN(0001¯) during MOVPE was investigated using density functional theory (DFT) calculations. The results confirm that the crucial factors for carbon incorporation are Fermi level pinning and accompanying surface band bending. In addition, the lattice symmetry has a strong dependence on the stability of carbon in a few subsurface layers, which results from interactions between the impurities and surface states. It was shown that these effects are responsible for facilitating or hindering the incorporation of impurities and dopants. The influence of diluent gas species (hydrogen or nitrogen) on carbon incorporation was discussed.

Growth and Properties of Intentionally Carbon‐Doped GaN Layers

“…There are some theoretical studies on surface states of nitride surfaces and also a recent paper on the impact of the surface structure on carbon incorporation. [18][19][20] However, the latter study is limited to potential incorporation sites for a single C atom. In this work, thick GaN layers were grown by HVPE and intentionally doped with carbon with the objective to identify the occupation site of carbon or its complexes experimentally.…”

CH4 Adsorption Probability on GaN(0001) and (000−1) during Metalorganic Vapor Phase Epitaxy and Its Relationship to Carbon Contamination in the Films

“…From the SEAQT analysis, a non-equilibrium state evolution of the adsorption process was obtained, and the adsorption probability was found to be 7.06 × 10 −3 in (0001) and 3.32 × 10 −6 in (000−1) at 1000 °C. A C impurity incorporation model was proposed here in which it was assumed that the C impurity concentration was proportional to the CH 4 adsorption probability and to the Boltzmann factor calculated from the energy of the C impurity at the first surface layer [51]. As a result of this model, the ratio of the C impurity concentration in (0001) to that in (000−1), cC(0001)/cC(000−1), was 1.25×101.…”

“…In 2017, Kempisty et al reported the depth profiles of the C impurity energy in (0001) and (000−1), i.e., the comparison of the total energies of two-surface slab models, where the one nitrogen atom at the selected layer near the surface (i.e., the 1st, 2nd, …, 8th, or 10th atomic layers from the surface) is substituted by a carbon atom [49]. Figure 7 shows the result of Reference [51] for 3Ga-H and 3N-H surfaces and the Boltzmann factors, exp(−E/kBT), at 1000 °C calculated from these energies. As can be seen, the C atoms at the fourth layer onwards from the surface were almost in the same situation as those in the bulk (i.e., layers deep enough).…”

“…Here, Pad is the CH 4 adsorption probability. Note that there are two kinds of sites with different stability in the (2 × 2) area: three triple sites and one single site (see Reference [51]). Subsequently, these C atoms are incorporated into deeper layers via a non-equilibrium process, which means that the cC at the first layer almost decides the cC at the bulk.…”

Oxygen Incorporation Kinetics in Vicinal m(10−10) Gallium Nitride Growth by Metal‐Organic Vapor Phase Epitaxy

“…Considerable research on the reduction of impurities in polar plane growth, such as þc(0001)and Àc(000À1)-plane growth, has been reported due to wide practical uses of the resulting materials. [6][7][8][9] Conversely, there have been few reports on impurity incorporation in the case of nonpolar plane growth, such as m(10À10)-plane growth, although layers grown without a polarization field along the growth direction are advantageous for device performances. [10] In 2018, Tanaka et al [11] reported that the oxygen concentration in GaN films grown on 5 off m-GaN toward the Àc-direction (Àc 5 off ) by metal-organic vapor phase epitaxy (MOVPE) was below that on 5 off m-GaN toward the þc-direction (þc 5 off ).…”