The electronic properties of
n
-InP(100) surfaces passivated with various sulfide solutions are studied using photoluminescence and Raman spectroscopy. It is shown that the passivation process leads ...to an increase in the photoluminescence intensity of the semiconductor, which indicates a decrease in the velocity of nonradiative surface recombination accompanied by a narrowing of the surface space-charge region and an increase in the electron density in the analyzed semiconductor bulk. The efficiency of electronic passivation of the
n
-InP(100) surface depends on the composition of the sulfide solution.
Photoluminescence, Raman spectroscopy and X-ray photoelectron spectroscopy are used to study electronic and atomic structure of
n
-InP(100) surfaces treated with different sulfide solutions. It is ...shown that the sulfide treatment causes removal of the native oxide layer from the semiconductor surface and formation of the passivating layer consisting of In–S chemical bonds with the structure dependent on the solution composition and atomic arrangement at the initial surface of the semiconductor. This is accompanied by an increase in photoluminescence intensity and narrowing of the surface depletion layer. Atomic structure of the passivating layer determines the total dipole that modifies the depth distribution of the bands potentials and thus the surface electronic structure.
The effect of chemical passivation in solutions of ammonium sulfide (NH
4
)
2
S on the optical and electronic properties of the surface
n
-InP (001) is studied. It is shown that treatment in a 4% ...aqueous solution of (NH
4
)
2
S leads to a twofold decrease in the surface field and charges localized in this region. Treatment in a 4% alcohol solution (NH
4
)
2
S leads to a decrease in these parameters by a factor of 3, and, moreover, the barrier photovoltage decreases by a factor of 3.
Various conditions of passivation of the GaSb(100) surface by ammonium sulfide ((NH
4
)
2
S) solutions depending on the solution concentration, solvent, and treatment time are investigated by X-ray ...photoelectron spectroscopy and atomic-force microscopy. It is shown that treatment of the GaSb(100) surface by any (NH
4
)
2
S solution leads to removal of the native oxide layer from the semiconductor surface and the formation of a passivating layer consisting of various gallium and antimony sulfides and oxides. The surface with the lowest roughness (RMS = 0.85 nm) is formed after semiconductor treatment with 4% aqueous ammonium sulfide solution for 30 min. Herewith, the atomic concentration ratio Ga/Sb at the surface is ~2. It is also found that aqueous ammonium sulfide solutions do not react with elemental antimony incorporated into the native-oxide layer. The latter causes a leakage current and Fermi-level pinning at the GaSb(100) surface. However, a 4% (NH
4
)
2
S solution in isopropanol removes elemental antimony almost completely; herewith, the semiconductor surface remains stoichiometric if a treatment duration is up to 13 min.
Sulfide Passivation of InP(100) Surface Lebedev, M. V.; Serov, Yu. M.; Lvova, T. V. ...
Semiconductors (Woodbury, N.Y.),
12/2020, Letnik:
54, Številka:
14
Journal Article
Recenzirano
Passivation of the
n
-InP(100) surface with sodium sulfide (Na
2
S) aqueous solution is analyzed by photoluminescence (PL) and X-ray photoelectron spectroscopy (XPS). The room-temperature PL ...intensity increases essentially even after short treatment with sulfide solution for 1 min. The enhancement in the room-temperature PL intensity after passivation decreases with the increase in the bulk doping level of the semiconductor. Time-resolved PL studies performed at liquid-nitrogen temperature indicate reduction in the surface recombination velocity. This improvement of the PL intensity occurs just after transformation of the native oxide layer consisting mainly of indium phosphates to the passivating layer consisting of indium sulfides and oxides. The surface bands in
n
-InP(100) remained nearly flat both before and after sulfide passivation.
The effect of sulphur surface passivation on the optical and electronic properties of InP was investigated. In the work, the approach of simultaneous measurement of the dynamics of the absorbed ...current and cathodoluminescence under continuous electron beam irradiation is used. This approach allows us to study the trapping of charge by traps and their influence on the luminescent properties. It was shown that hole traps are observed in the samples; moreover, the localization of a positive charge leads to an increase in the luminescence intensity. Passivation was found to significantly reduce the number of hole traps.
The changes in the stoichiometry and morphology of the GaSb(100) surface in the process of sulfide passivation with aqueous and alcoholic ammonium sulfide solutions were studied by AFM and XPS. It ...was found that after sulfide treatment the Ga/Sb ratio can vary in the range from 0.13 to 3, while the surface roughness can be changed from 1.1 to 5.5, depending on the concentration of the (NH4)2S solution, solvent and passivation time.
•Treatment of InSb (001) substrate with 1M aqueous Na2S solution results in nearly complete removal of native oxides.•A sulfide protective layer formed by the S-treatment is desorbed at much lower ...temperatures than the native oxide layer.•The bulk InSb epilayers grown on the S-treated substrates have very smooth surface (RMS ∼0.1nm).•Good structural quality of the homointerfaces formed at the S-treated substrates is confirmed by TEM.
The aqueous sodium sulfide solution has been used for pre-epitaxial preparation of epi-ready InSb (001) substrates for molecular beam epitaxy (MBE) of InSb layers. X-ray photoemission spectroscopy study shows that the S-treated surface of InSb (001) substrate generally does not contain a native oxide layer and is covered with a sulfide protecting overlayer. Atomic-force microscopy and transmission electron microscopy have been applied to compare surface topography and structural properties of InSb layers grown by MBE on S-treated and untreated epi-ready InSb (001) substrates. The MBE growth of InSb layers with very smooth surface possessing the root-mean-square roughness as low as 0.1nm and good structural quality has been demonstrated on the S-treated substrates.
Passivation of the n-InP(100) surface with an aqueous solution of sodium sulphide (Na2S) has been investigated by spectroscopic photoluminescence (PL). After sulphide treatment the PL signal ...intensity of InP increased significantly and this increase is dependent on duration of sulphide passivation. The correlation of the increase in the PL intensity after sulphide treatment with the variation of the solution pH in contact with InP(100) surface has been established, that expect the possibility for optimization of the passivation process by monitoring the change of the solution pH value in the course of sulphide treatment of the semiconductor.
Photoreflectance of indium antimonide Komkov, O. S.; Firsov, D. D.; Lvova, T. V. ...
Physics of the solid state,
12/2016, Letnik:
58, Številka:
12
Journal Article
Recenzirano
The photoreflectance spectra of
n
-InSb layers were measured using photomodulation Fourier transform infrared spectroscopy. The samples were grown by molecular beam epitaxy on heavily doped
n
+
...-InSb(001) substrates annealed under different conditions. The strength of the near-surface electric field was determined from the period of the Franz–Keldysh oscillations observed in the photoreflectance spectra. It was noted that the strength of the electric field increases during a long-term storage of the samples in air. The treatment of
n
-InSb layers in a 1M aqueous solution of Na
2
S led to an increase in the measured field. Previously, it was shown that, after this treatment, the surface Fermi level is shifted deep into the conduction band and, probably, does not depend on the conditions and time of the preliminary storage of the samples. With the use of passivation in Na
2
S, the optical method developed in this study allows for the contactless measurement of the concentration of electrons in
n
-InSb homoepitaxial layers.
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