Near-surface electronic structure on InAs(100) modified with self-assembled monolayers of alkanethiols

Abstract

Using surface chemical modification to eliminate the generic problems of high surface recombination velocity and Fermi level pinning is studied on InAs( 100). Raman scattering and X-ray photoelectron spectroscopy (XPS) are used to investigate passivation, provided by alkanethiols, RSH; R = CH3(CH2). both neat and in ethanolic solutions, of this surface against oxidation. The magnitude of the interracial bandbending is obtained by analysis of Raman scattering from the unscreened LO phonon, which arises from the near -surface charge accumulation region (CAR). Removing the native oxide with a Br:CH30H chemomechanical etch reduces the surface band bending, but atmospheric oxidation increases band bending to its original level over several hours.Chemical passivation prevents band-bending for periods up to several weeks. DISCLAIMER DISCLAIMERPortions of this document may be illegible in electronic image products.Images are produced from the best availabie original document. Samples were etched in a 1YO Brz:CHJOH (Br:MeOH) solution for 30s and kept in NL to prevent oxide growth between the etch and passivation steps. Profilometry on stepprofiles determined the etch rate to be 27 + 4~/s . Passivations were carried out in both neat alkanethiol and 1 mM solutions of alkanethiol in deaerated ethanol.The Raman spectrum of InAs exposed to various processing steps is given in Figure 1. The spectrum of the unprocessed sample shows two modes: a low-frequency coupled phonon-plasmon mode, L+ observed near 225 cm-', originating in the bulk of the n+-hu%, and an unscreened LO mode observed at 239 cm-' originating from the CAR as a result of wavevector non-conservation.The narrow width of the CAR is associated with uncertainty in the scattering wavevector: scattering from regions of k-space corresponding to wavelengths smaller than the Thomas-Fermi screening length is observed7. In a series of similarly prepared and processed samples the LO mode intensity can be taken to reflect the spatial extent of the CAR and, by inference, the magnitude of the surface state density pinning the surface Fermi Ievel.zsComparing the spectra before and immediately after etching shows a decrease in the unscreened LO mode intensity. Also shown in Fig. 1 is the result of exposing the freshly etched sample to atmospheric 02 for varying times. Without passivation the LO mode, quenched by etching, is observed to regenerate within a few hours. Figure 2 shows the effect of storing the sample in dry N2, removing the sample only periodically for Raman measurements. A small increase in LO intensity is observed after the first measurement, which subsequently stabilizes. We infer from these observations that exposure to 02 repins the Fermi level above the conduction band. Apparently, surface oxidation plays a more significant role in Fermi level re-pinning than crystal termination and reconstruction.To study the passivation of InAs(100) freshly etched samples were treated with 1 mM ethanolic solutions of alkanethiol: octadecanethiol, n = 17, hexadecanet...

Sulphur-induced electron accumulation on InAs: a comparison of the (001) and (111)B surfaces

“…It remains to discuss why the present results and the others indicating sulphur-induced enhance- ment of downward band bending at InAs surfaces [6][7][8] differ from the reduction of band bending reported by both Bezryadin et al [3] and Tanzer et al [4]. Significantly, in the latter studies, the sulphur-treated surfaces exhibit a lower surface state density than the native oxide-terminated surfaces.…”

“…Several reports on the effects of sulphur treatment on the electronic properties of InAs claimed to show evidence of a reduction in the downward band bending and an associated lowering of the surface state density [3,4], consistent with electrical passivation of the InAs surface. However, Watanabe and Maeda [5] adsorbed an alternative chalcogen, selenium, on the InAs(0 0 1) surface and found evidence of an increase in the downward band bending.…”

Модификация Атомной И Электронной Структуры Поверхности Полупроводников А-=sup=-Iii-=/Sup=-В-=sup=-v-=/Sup=- На Границе С Растворами Электролитов О Б З Ор

“…Адсорбция органических молекул применялась для изменения электронных свойств поверхностей полупроводников А III В V [133,[145][146][147] и модификации характеристик полупроводниковых приборов [139,144,[148][149][150]. Однако в основном адсорбция органических молекул используется для химической пассивации, т. е. для стабилизации поверхности полупроводников А III В V в атмосфере, растворах электролитов и в физиологических растворах с целью создания биоинтерфейсов [151][152][153][154], а также для обеспечения биосовместимости полупроводников А III В V [151,155,156] и приборов на их основе [157].…”

Dip-pen nanolithography on etched InAs(100) using homogeneous and mixed ink solutions

“…1 This observation carries important implications for the creation of InAs͑100͒ devices where the prevention of nonradiative defects is integral to the fabrication scheme. 3,[5][6][7] In order to expand the utility of III-V semiconducting materials to versatile chemical and biological detection platforms it is also of interest to explore patterning methods on these surfaces. 3,[5][6][7] In order to expand the utility of III-V semiconducting materials to versatile chemical and biological detection platforms it is also of interest to explore patterning methods on these surfaces.…”