Sulfide and Fluoride Ions Based Passivation of GaAs(100) Surface and Concept of Combining Surface Passivation with Tunnel Junction Based Molecular Devices (original) (raw)
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2021
GaAs surface is characterized by a high density of surface states, which preclude the utilization of this semiconducting material for the realization of several advanced devices. Sulphur-based passivation has been found significantly useful in reducing the effect of dangling bonds. In this article first, the problem associated with GaAs surface has been discussed in a tutorial form. Secondly, the brief introduction of a wide variety of surface passivation methods was introduced. Sulphur passivation, the most effective surface state quenching method, has been elaborated. Thirdly, current trends in the field of surface passivation of GaAs surface has been discussed. Our discussion also focusses on utilizing GaAs and alloys for the molecular electronics and molecular spintronics and based on our insights in the GaAs (P. Tyagi, MRS Advances 2 (51), 2915-292
Sulphide passivation of GaAs: the role of the sulphur chemical activity
Semiconductor Science and Technology, 1998
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.
Solvent effect on the properties of sulfur passivated GaAs
Journal of vacuum science & technology. B, Microelectronics and nanometer structures: processing, measurement, and phenomena: an official journal of the American Vacuum Society
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. © 1996 American Vacuum Society
Journal of Physics Condensed Matter
We have studied the efficacy of (NH4)2Sx surface passivation on the (311)A GaAs surface. We report XPS studies of simultaneously-grown (311)A and (100) heterostructures showing that the (NH4)2Sx solution removes surface oxide and sulfidizes both surfaces. Passivation is often characterized using photoluminescence measurements, we show that while (NH4)2Sx treatment gives a 40 - 60 x increase in photoluminescence intensity for the (100) surface, an increase of only 2 - 3 x is obtained for the (311)A surface. A corresponding lack of reproducible improvement in the gate hysteresis of (311)A heterostructure transistor devices made with the passivation treatment performed immediately prior to gate deposition is also found. We discuss possible reasons why sulfur passivation is ineffective for (311)A GaAs, and propose alternative strategies for passivation of this surface.
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
Dual passivation of GaAs (110) surfaces using O2/H2O and trimethylaluminum
The Journal of Chemical Physics, 2013
The nucleation and passivation of oxide deposition was studied on defect-free GaAs (110) surfaces to understand passivation of surfaces containing only III-V heterobonds. The passivation process on GaAs (110) was studied at the atomic level using scanning tunneling microscopy while the electronic structure was determined by scanning tunneling spectroscopy (STS). The bonding of the oxidant and reductant were modeled with density functional theory. To avoid Fermi level pinning during gate oxide atomic layer deposition, a dual passivation procedure was required using both a reductant, trimethylaluminum (TMA), and an oxidant, O 2 or H 2 O. Dosing GaAs (110) with TMA resulted in the formation of an ordered complete monolayer of dimethylaluminum which passivates the group V dangling bonds but also forms metal-metal bonds with conduction band edge states. These edge states were suppressed by dosing the surface with oxidants O 2 or H 2 O which selectively react with group III-aluminum bonds. The presence of an ordered Al monolayer with a high nucleation density was indirectly confirmed by XPS and STS.
Journal of Applied Physics, 2010
The interactions of oxygen atoms on the GaAs͑001͒-2͑2 ϫ 4͒ surface and the passivation of oxidized GaAs͑001͒-2͑2 ϫ 4͒ surface were studied by density functional theory. The results indicate that oxygen atoms adsorbed at back-bond sites satisfy the bond saturation conditions and do not induce surface gap states. However, due to the oxygen replacement of an As dimer atom at a trough site or row site, the As-As bond is broken, and gap states are produced leading to the Fermi level pinning because of unsaturated As dangling bonds. Atomic H, Cl, S, F, and the molecular species GaO were examined to passivate the unsaturated As dangling bond. The results show that H, Cl, F, and GaO can remove such gap states. It is also found that the interaction of S with the unsaturated As dangling bond does not remove the gap states, and new gap states are generated upon single S adsorption. A higher S coverage forms S-S dimer pairs which passivate two unsaturated As atoms, and removes the As-induced gap states.
Sulfur passivation effect on HfO2/GaAs interface: A first-principles study
2011
The impact of sulfur passivation on the structural and electronic properties of the HfO 2 / GaAs interface is investigated by density functional theory with a hybrid functional. The gap states at the HfO 2 / GaAs interface arise from three major contributions: Ga 3+ and partial oxidation, As-As dimers, and Ga dangling bonds. By introducing S atoms at the interface, the removal of the gap states within the lower half of the GaAs band gap is observed, while the gap states in the upper half are pushed upward by ϳ0.15 eV.