Wet Etching of GaAs(100) in Acidic and Basic Solutions: A Synchrotron−Photoemission Spectroscopy Study (original) (raw)
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Etching of GaAs(100) with Aqueous Ammonia Solution: A Synchrotron-Photoemission Spectroscopy Study
The Journal of Physical Chemistry C, 2010
Etching of the GaAs(100) surface with aqueous ammonia solution is studied by highly surface-sensitive synchrotron-radiation photoemission spectroscopy. It is shown that such treatment effectively removes the native oxide layer leaving the surface covered with elemental arsenic, as well as arsenic hydroxides AsOH and As(OH) 3 , gallium hydroxide GaOH, and gallium suboxide Ga x O. After annealing of the surface at 500°C
Applied Surface Science, 2004
Synchrotron-induced photoelectron spectroscopy was used to investigate the native-oxide-covered GaAs(1 0 0) surface and changes induced by etching with aqueous ammonia solution and by annealing in vacuum. The etching step removes arsenic and gallium oxides from the surface and the surface gets covered by elemental arsenic and tiny amounts of gallium suboxide. The surface oxygen content is reduced by an order of magnitude after etching, whereas the surface carbon content is somewhat increased. Annealing of this surface at 450 8C results in the disappearance of elemental arsenic and a considerable decrease in surface carbon and oxygen contents. The valence band spectra exhibit clear features typical for As-terminated GaAs(1 0 0) surfaces, as also obtained after As decapping. #
Characterization of wet-etched GaAs (100) surfaces
Surface and Interface Analysis, 2005
To enable the use of GaAs-based devices as chemical sensors, their surfaces must be chemically modified. Reproducible adsorption of molecules in the liquid phase on the GaAs surfaces requires controlled etching procedures. Several analytical methods were applied, including Fourier transform infrared spectroscopy (FTIRS) in attenuated total reflection and multiple internal reflection mode (ATR/MIR), high-resolution electron energy loss spectroscopy (HREELS), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) for the analysis of GaAs (100) samples treated with different wet-etching procedures. The assignment of the different features due to surface oxides present in the vibrational and XPS spectra was made by comparison with those of powdered oxides (Ga 2 O 3 , As 2 O 3 and As 2 O 5 ). The etching procedures here described, namely, those using low concentration HF solutions, substantially decrease the amount of arsenic oxides and aliphatic contaminants present in the GaAs (100) surfaces and completely remove gallium oxides. The mean thickness of the surface oxide layer drops from 1.6 nm in the raw sample to 0.1 nm after etching. However, in presence of light, water dissolution of arsenic oxides is enhanced, and oxidized species of gallium cover the surface.
Chemical etching of (100) GaAs in a sulphuric acid-hydrogen peroxide-water system
Journal of Materials Science, 1987
A detailed investigation of the etching of (1 00) GaAs in H2SO4-H202-H20 systems has been made. The influence of the concentration of particular etchant components on etching rate and on the shape of the crystal surface was examined. From these resuRs the Gibbs" triangle of etching bath compositions was divided into parts corresponding to the various states of the crystal surfaces and various etching mechanisms. The shape of the crystal surface after etching was closely related to the profiles of the grooves etched in the [1 1 0] direction in the same solution.
Etching or Stabilization of GaAs(001) under Alkali and Halogen Adsorption
The Journal of Physical Chemistry C, 2012
Experimentally and by ab initio calculations it is shown that adsorption of electropositive cesium on the As-rich surface of GaAs(001) and, in a symmetric fashion, adsorption of electronegative iodine on the Ga-rich surface, induce a decrease of the surface stability, thus facilitating surface etching. Conversely, Cs adsorption on the Garich surface and I adsorption on the As-rich surface lead to an increased surface stability. Etching occurs when adsorption-induced charge transfer weakens the backbonds of the top arsenic atoms for the case of Cs on the As-rich β2(2 × 4) surface and the lateral bonds in the topmost surface layer for I on the Ga-rich ζ(4 × 2) surface. The possibilities of reversible transitions between the two reconstructed surfaces and of atomic layer etching with monolayer precision are demonstrated.
Reconstruction dependence of the etching and passivation of the GaAs(001) surface
JETP Letters, 2010
The methods of the layer by layer or "digital" etching of crystals, which makes it possible to control lably remove monolayers of a crystal and to maintain the atomic smoothness of the surface, have been actively developed in the last two decades. The cre ation of heterostructures for nanoelectronic investiga tions requires not only the layer by layer growth but also layer by layer etching of semiconductors. The dry (gas phase) etching methods such as reactive ion and ion beam etchings, which are widely used in the tech nology of the production of semiconducting struc tures, do not provide the control of etching at the atomic level. The layer by layer etching of III-V semiconducting compounds can be implemented by using adsorbates selectively reacting with atoms of group III or V.
Investigation of neutralized (NH[sub 4])[sub 2]S solution passivation of GaAs (100) surfaces
Applied Physics Letters, 1997
Synchrotron radiation photoelectron spectroscopy combined with scanning electron microscopy ͑SEM͒ and gravimetry has been used to study GaAs ͑100͒ surfaces treated with a neutralized ͑NH 4 ͒ 2 S solution. Compared to the conventional basic ͑NH 4 ͒ 2 S solution treatment, a thick Ga sulfide layer and strong Ga-S bond were formed on the GaAs surface after dipping GaAs wafers in a neutralized ͑NH 4 ͒ 2 S solution. Gravimetric data show that the etching rate of GaAs in the neutralized ͑NH 4 ͒ 2 S solution is about 15% slower than that in the conventional ͑NH 4 ͒ 2 S solution. From SEM observation, fewer etching pits with smaller sizes were found on the neutralized ͑NH 4 ͒ 2 S-treated GaAs surface. © 1997 American Institute of Physics. ͓S0003-6951͑97͒01247-3͔
Surface passivation and morphology of GaAs(100) treated in HCl-isopropanol solution
Applied Surface Science, 2004
A promising chemical surface preparation technique, which consists in the treatment of GaAs(1 0 0) in HCl-isopropyl alcohol (HCl-iPA) solution under nitrogen atmosphere, is further developed. It was shown earlier [Tereshchenko et al., J. Vac. Sci. Technol. A 17 (1999) 2655] that HCl-iPA treatment and subsequent anneals in vacuum yielded atomically clean GaAs(1 0 0) surface with the whole range of surface reconstructions characteristic of this crystal face. In the present work the mechanisms of the passivation of GaAs(1 0 0) surfaces by arsenic overlayers as a result of HCl-iPA treatment are experimentally studied by X-ray photoelectron spectroscopy, low-energy electron diffraction and atomic force microscopy. The HCl-iPA treatment of clean As-stabilized GaAs(1 0 0) surfaces results in chemical passivation of the surface by submonolayer amount of excess arsenic. For the initially oxidized surfaces the treatment leads to the formation of 1-3 monolayers of amorphous arsenic on the surface, with the major part of the arsenic originating from the surface oxides dissolved in HCl-iPA. The HCl-iPA treatment preserves the atomic flatness of the GaAs(1 0 0) surface, keeping the mean roughness on a very low level of approximately $0.1 nm.
Interaction of 2-Propanol with the GaAs(100) Surface
The Journal of Physical Chemistry C, 2009
Synchrotron photoemission spectroscopy is applied to study the interaction of 2-propanol with the clean GaAs(100) surface to understand the solid-solvent interaction at the semiconductor/electrolyte interface. Adsorption of 2-propanol molecules at liquid-nitrogen temperature and emersion of the semiconductor from liquid 2-propanol at room temperature are performed to gain a more detailed insight into surface reaction steps and processes involved. It is found that on adsorption at liquid-nitrogen temperature a 2-propanol molecule dissociates on a GaAs(100) surface to a hydrogen atom, which is adsorbed on an As atom that is part of an As-As dimer, and a 2-propoxy group, which adsorbs to an adjacent Ga atom. On a GaAs(100) surface emersed from liquid 2-propanol at room temperature, two different states of dissociative adsorption are observed. The first state corresponds to dissociation of a 2-propanol molecule into a hydrogen atom and a 2-propoxy group. The second state corresponds to dissociation into an OH group and a 2-propyl radical. On the GaAs(100) surface neither adsorption of 2-propanol molecules nor emersion from liquid 2-propanol causes destruction of the As-As dimer structure.