S. Yu. Davydov

The effect of spontaneous polarization of hexagonal regions of a trilayer NH/3C/NH heterostructure on the relative position of the bands has been considered within the model previously proposed for the description of the NH/3C heterojunction. Considerable attention has been focused on the study of the effect of spontaneous polarization and thickness of the 3C region on the energy characteristics of the quantum wells formed near heterojunctions.

The values of spontaneous polarization and permittivities of aluminum, gallium, and indium nitrides, as well as silicon carbide, with a wurtzite structure are calculated within the Harrison bond-orbit

The effect of the electrostatic field caused by spontaneous polarization in hexagonal plates of a heterostructure based on NH-SiC/3C-SiC/NH-SiC silicon carbide polytypes on relative positions of energy bands is considered. It was shown that the asymmetry arising in the system is associated with the superposition of polarization and contact fields.

A change in the substrate work function has been calculated using the Anderson-Newns model for H/ZnO, O₂/ZnO, and O₂/TiO₂ systems in the interval of submonolayer adsorbate coverages (0 ≤ Θ ≤ 1). Using the relation ΔG/Δϕ = const obtained previously, where ΔG and Δϕ are changes in the surface conductivity and work function, the values of ΔG(Θ) are evaluated, which show a good agreement with the experimental data.

The problem of three-layer NH-SiC/3C-SiC/NH-SiC heterostructures was considered within the model previously proposed for describing the heterojunction between NH-SiC/3C-SiC silicon carbide polytypes,

The Haldane-Anderson model previously used for describing the adsorption on a crystalline substrate is generalized to the case of an amorphous substrate. It is demonstrated that the main difference between the occupation numbers of the adatom is observed in the case where the atomic level overlaps with the band gap (for a crystalline semiconductor) and the mobility gap (for an amorphous semiconductor). The adatom charge on the amorphous substrate is smaller than that on the crystalline substrate.

The effect of a polycrystalline substrate on the charge of adatoms and on the work function is considered in terms of the Anderson-Newns model. Polycrystallinity is characterized by deviation δϕ _i of the work function of the ith face from mean value 〈ϕ _i 〉. It is found that polycrystallinity leads to an increase in the occupation numbers of adatoms as compared to absorption on a monocrystalline surface. This leads to a decrease in the value of charge in the case of electropositive adsorption and to an increase in its value in the case of electronegative adsorption. It is shown that the polycrystallinity effect must be manifested most strongly in the case of adsorption of gases at metals and semiconductors.

We have studied the effect of spontaneous polarization, which is inherent in noncubic silicon carbide (SiC) polytypes, on the characteristics of quantum wells (QWs) formed in the cubic region at the heterojunction. The analysis is performed for various QW models, including triangular, parabolic, and exponential. Conditions for the appearance of a two-dimensional electron gas at the interface are briefly discussed.

Analytical expressions describing the change in the surface conductivity (ΔG) as a result of the adsorption of positively and negatively charged atoms are obtained. It is shown that the ratio of ΔG to the adsorption-induced change in the work function (Δϕ) rather weakly depends on the surface coverage with adatoms.