Ultrathin (1×2)-Sn layer on GaAs(100) and InAs(100) substrates: A catalyst for removal of amorphous surface oxides

Abstract

Amorphous surface oxides of III-V semiconductors are harmful in many contexts of device development. Using low-energy electron diffraction and photoelectron spectroscopy, we demonstrate that surface oxides formed at Sn-capped GaAs͑100͒ and InAs͑100͒ surfaces in air are effectively removed by heating. This Sn-mediated oxide desorption procedure results in the initial well-defined Sn-stabilized ͑1 ϫ 2͒ surface even for samples exposed to air for a prolonged time. Based on ab initio calculations we propose that the phenomenon is due to indirect and direct effects of Sn. The Sn-induced surface composition weakens oxygen adsorption. © 2011 American Institute of Physics. ͓doi:10.1063/1.3596702͔Amorphous ͑or polycrystalline͒ oxide layers are easily formed at the surfaces of III-V semiconductors exposed to oxygen. The formation of such structurally and electronically poor III-V oxide layers is detrimental for the development of many types of devices. Detrimental effects include surface Fermi-level pinning in the III-V channel of metal-oxidesemiconductor field-effect transistors ͑MOSFETs͒, increased surface recombination, barrier formation within metalsemiconductor contacts, and surface contamination affecting regrowth processes. The first example is probably the best known; the formation of amorphous surface oxides at the interface between a III-V semiconductor and an insulator causes the Fermi level to pin via defect states, thus rendering the development of III-V channels difficult for practical MOSFETs. A significant effort has therefore been made to understand how III-V oxides can be removed ͑or their formation prevented͒ during the fabrication of insulator-III-V junctions. 1-12 However, it is still unclear whether it is possible to avoid the oxygen reaction during interface growth, and there is still much room to improve insulator-III-V interfaces and our overall understanding of III-V oxidation. Simultaneously, an increasing number of studies 5,[13][14][15][16][17][18][19] has revealed the importance of atomic-scale information and of the processing of semiconductor surfaces, so-called surface engineering, for controlling the properties of the semiconductor interfaces. These studies have shown that a properly chosen thin adsorbate layer with a well-defined structure significantly improves the properties of oxide-semiconductor interfaces for various types of semiconductor devices.In this letter, we report an interesting effect of Sncapping on the desorption properties of amorphous oxides of GaAs͑100͒ and InAs͑100͒ surfaces. In particular, we have found that the initial Sn-stabilized ͑1 ϫ 2͒-ordered GaAs and InAs surfaces, comprising 0.5-1.0 monolayer ͑ML͒ of Sn, can be restored even after a week's exposure to air; in other words, the native surface oxides formed can be efficiently removed by heating the substrates in a vacuum. This property may be useful not only for the development of the longsought III-V MOSFETs but also for example for the development of Ohmic contacts and re-growth applications.Deposition of 0....

Synthesis and Characterization of Layered Tin Monoxide Thin Films with Monocrystalline Structure on III–V Compound Semiconductor

“…Thus, the shift comparison supports that the film composition is SnO rather than SnO 2 . It is worth noting that directly after the air exposure of the Sn‐covered InAs substrate, we have observed the formation of the SnO 2 phase that causes the energy shifts, which are clearly larger than those in Figure . The analysis of O 1s spectra (Figure S1 in Supporting Information) also supports the formation of SnO.…”

“…Various amounts of Sn, i.e ., 1−5 monolayers (ML) were deposited onto the clean InAs(100)c(8 × 2) substrate kept at room temperature in ultrahigh vacuum (UHV) conditions. Post‐heating the Sn‐covered substrate in UHV at 350−400 °C produced a Sn‐covered InAs substrate with a (1 × 2) reconstruction, which often contained also three‐dimensional Sn clusters. Then the sample was exposed to the molecular O 2 gas flow in the UHV chamber for 10−20 min under a pressure of 3−4 × 10 –6 mbar at a substrate temperature of 350−450 °C to form the SnO film.…”

Bridging the gap between surface physics and photonics

“…The strongly rearranged III-V(100) surfaces can be in fact expected to cause atomic scale non-uniformity at the interfaces grown on the top of the reconstruction. Thus, a proper adsorbate layer on a clean semiconductor surface might decrease the structural changes at the semiconductor side via the formation of smaller adsorbate-induced unit cell [151][152][153], and improve atomic-scale smoothness at the interfaces. Wurtzite III-V nitride surfaces (figure 9(e)) such as GaN(0001) and AlGaN(0001) are an exception among semiconductor surfaces because their reconstructions are typically atomically smooth, which can be understood with strong nitrogen bonds which have partial ionic nature, which hinders the atomic rearrangement [137,[154][155][156][157][158][159].…”