Mikhail V. Lebedev

Chalcogenide passivation of III-V semiconductor surfaces

Experimental studies of chalcogenide passivation (by sulfur and selenium atoms) of III–V semiconductor surfaces are analyzed. The characteristic features of chemical-bond formation, the atomic structure, and the electronic properties of III–V semiconductor surfaces coated with chalcogenide atoms are examined. Advances in recent years in the application of chalcogenide passivation in semiconductor technology and trends and prospects for further development of this direction are discussed.

Solvent effect on the properties of sulfur passivated GaAs

Photoluminescence and x‐ray photoelectron spectroscopy have been used to study the solvent effect on surface properties of GaAs passivated in different sulfide solutions. It has been found that sulfur passivation could be made more efficient by decreasing the solution dielectric constant through the use of various alcohols as solvents. Specifically, the band edge photoluminescence intensity is much higher, the total amount of oxides is lower, and sulfur coverage is higher compared with a GaAs surface treated in an aqueous sulfide solution. The role of the solvent in sulfur passivation is discussed.

Surface modification of III–V semiconductors: chemical processes and electronic properties

Abstract The possibilities of controlling the surface electronic properties of III–V semiconductors by varying the adsorption chemistry are analyzed. Variations of the adsorption process parameters and the adsorbate reactivity are able to affect the surface atomic and electronic structure of the semiconductor. The adsorbate reactivity is considered within the framework of the density functional theory using the reactivity indices. The easiest way to affect the reactivity of a particular adsorbate is to create a solvation shell around it, as is possible in both liquid solutions and the gas phase (microsolvation). Solvation of ions before their adsorption by different solvents affects considerably the relative nucleophility of the central atom in the ion, which results in a different charge transfer mechanism from the surface states on adsorption, and thus, in a different modification of the surface electronic structure of the semiconductor. The effect of halogen, sulfur and metal atoms reactivity on the electronic structure of the resulting adsorbate-covered surface of III–V semiconductor is discussed.

Sulphide passivation of GaAs : the role of the sulphur chemical activity

The passivation of n-GaAs in different sulphur containing solutions in which sulphur chemical activity was varied, i.e. solutions of sodium and ammonium sulphides in water and alcohols, as well as a solution of sulphur monochloride in carbon tetrachloride, was studied by photoluminescence and Raman spectroscopy. The increase of the sulphur chemical activity in the passivating solution results in an increase of the photoluminescence intensity and in a decrease of the surface barrier of the passivated semiconductor.

Raman scattering study of surface barriers in GaAs passivated in alcoholic sulfide solutions

Raman scattering has been used to study the variation of surface barriers in GaAs due to sulfur passivation in solutions of ammonium sulfide [(NH4)2S] in different alcohols (ethanol, isopropanol, and tert-butanol). It has been found that the surface barrier height and the depletion layer width decrease considerably with the decrease of the dielectric constant of the passivating solution.

Electronic properties of GaAs(100) surface passivated in alcoholic sulfide solutions

Using Raman spectroscopy and the Kelvin probe method the surface band bending and electron work function of GaAs(100) passivated in aqueous and alcoholic solutions of ammonium sulfide have been studied. It is shown that the solvent strongly affects the position of energy levels on the sulfide-treated surface. With the decrease of the solution dielectric constant the surface band bending decreases and the electron work function increases both in n-GaAs and p-GaAs. The ionisation energy of the semiconductor increases after sulfur treatment and in n-GaAs it increases with the decrease of the dielectric constant of the solution.

Sulfidization of GaAs in alcoholic solutions: a method having an impact on efficiency and stability of passivation

Abstract Photoluminescence and XPS were used to show that the effectiveness of GaAs sulfur passivation could be increased by using sulfide solutions in which alcohols with a low dielectric constant are used as solvents. It has been found that with the decrease in the solvent dielectric constant, in such solutions the surface sulfur coverage increases, the thickness of the native oxide layer decreases, and the efficiency of band-edge photoluminescence increases.

Sulfide passivation of III–V semiconductors: Kinetics of the photoelectrochemical reaction*

A phenomenological model is proposed to describe sulfide passivation of the surfaces of III–V semiconductors as a process of charge transfer between a semiconductor and a passivation solution. The model assumes that formation of the passivation sulfide coat occurs as a result of oxidation of the semiconductor in a photoelectrochemical reaction. The growth rate of the passivating coat is determined by the rate at which electrons are transferred from the semiconductor into the solution, as well as by the energy which binds atoms in the surface layer of the semiconductor and the heat evolving in the process. It is found that the growth rate of the coat is dependent upon conductivity type and doping level of the semiconductor, hydrogen ion exponent, and concentration of the solution and, as well, the intensity of light incident upon the electrolyte/semiconductor interface. In terms of the model, passivation of different III–V semiconductors is considered.

Sulfur passivation of InGaAs/AlGaAs SQW laser (977 nm) facets in alcohol-based solutions

Abstract Sulfide treatment of InGaAs/AlGaAs SWQ lasers ( λ = 977 nm) in alcohol-based solutions increases the catastrophic optical damage limit. This increase is largest (50%) when the solvent with the lowest dielectric constant ( tert -butanol) is used.

Valence band photoemission, band bending, and ionization energy of GaAs(100) treated in alcoholic sulfide solution

Valence band and Fermi level position on a p-GaAs(100) surface treated in the solution of ammonium sulfide in isopropanol have been studied by ultraviolet photoemission spectroscopy. Sulfur treatment and subsequent annealing affect features of 0.8 and 3.7 eV binding energy in normal emission valence band spectrum of a bare semiconductor and the effect is related to the variation of surface chemical bonds. It has been found that after sulfur treatment surface band bending and ionization energy increase by 0.4 and 0.3 eV, respectively. Annealing at 310 °C or higher results in the decrease of the ionization energy with the temperature. The position of the surface Fermi level sharply changes from 1.5–1.20 to 0.85 eV above the valence band maximum when the surface is annealed at 360 °C.