V. N. Bessolov

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.

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.

Sulfide passivation of III-V semiconductor surfaces: role of the sulfur ionic charge and of the reaction potential of the solution

A model is proposed for describing the effect of a solution on the electronic properties of sulfided surfaces of III-V semiconductors which treats the adsorption of sulfur in terms of a Lewis oxide-base interaction. According to this model, the density of states on a sulfided surface, which pin the Fermi level, decreases as the global hardness of the electron shell of the adsorbed sulfide ions is increased. The Thomas-Fermi-Dirac method is used to calculate the global hardness of sulfide ions with different charges as a function of the dielectric constant of the medium. It is shown that the hardness of a sulfur ion is greater when its charge is lower and the dielectric constant of the solvent is lower.

Sulfide passivation of III–V semiconductors: The starting electronic structure of a semiconductor as a factor in the interaction between its valence electrons and the sulfur ion

In the experiments on GaAs, InP, and GaP treated in aqueous solutions of Na2S:9H2O, it has been shown that in the process of sulfide passivation of III–V semiconductors a significant role is played by both the starting electronic structure of the semiconductor surface (prior to sulfidizing) and the energy state of the sulfur ion in solution. A model of the interaction of the sulfur ion in a solution with the valence electrons of a III–V semiconductor in the course of the sulfidizing process has been suggested and verified. During the interaction process, a change takes place in the electrochemical potential (Fermi level) of the semiconductor, which affects the electron work function at the surface. Between various semiconductors the amount of this change in the work‐function value varies in proportion to the negative of the starting electron work‐function value in the untreated semiconductor and depends on the treatment temperature. In a semiconductor such that its starting work‐function value is equal to...

Structural characterization of GaN epilayers on silicon: Effect of buffer layers

Cross-sections of GaN/AlN/3C-SiC/Si(111) system have been studied by electron microscopy techniques. A nanometer thick buffer layer of silicon carbide on Si(111) substrate was formed using an original solid-phase epitaxy method. The subsequent layers of gallium nitride and aluminum nitride were grown by the method hydride-chloride vapor phase epitaxy. The resulting GaN layers display neither threading dislocations nor cracks on any scale. The main fraction of defects in GaN layers have the form of dislocation pileups that are localized at and oriented parallel to the GaN/AlN interface. The dislocation density in the obtained GaN layers is (1–2) × 109 cm−2, which corresponds to a minimum level reported in the available literature. The buffer AlN layer contains nanopores, which reduce the level of stresses at the GaN/AlN interface and thus almost completely inhibit the formation of threading dislocations.