Passivation of GaAs(111)A surface by Cl termination

Abstract

It is found that an ordered and air-stable GaAs͑111͒A-͑1ϫ1͒-Cl surface can be produced by chemical etching/passivation with dilute HCl solution. The synchrotron polarization-dependent Cl K-edge x-ray absorption near-edge structure and x-ray photoelectron spectroscopy studies showed that the surface is terminated with Ga-Cl bonds oriented along the surface normal. Low-energy electron diffraction studies showed a bulklike ͑1ϫ1͒ structure on the Cl-terminated GaAs͑111͒A surface. The Cl termination eliminates surface band-gap states caused by surface oxides. Photoluminescence measurements showed a dramatic increase in the near-band radiative emission rate corresponding to reduction in the occupied surface band-gap states. A reduction of surface gap states by Cl termination was confirmed by surface photovoltage measurements.

Properties of GaP(001) surfaces chemically treated in NH4OH solution

“…Note that such an ideal condition could never be achieved in practice. Figure 1 shows the pseudodielectric-function spectra ͗ ͑E͒͘ for GaP͑001͒ surface treated in NH 4 OH solution for t = 1 and 2 s, together with that obtained from as-received sample ͑t =0 s͒. For comparison, the ͗ ͑E͒͘ spectrum for a clean, nearly flat GaP surface is shown by the bold solid lines.…”

“…In this article, we report on the chemical treatment effects of GaP͑001͒ surfaces in NH 4 OH solution studied using spectroscopic ellipsometry ͑SE͒, ex situ atomic force microscopy ͑AFM͒, x-ray photoelectron spectroscopy ͑XPS͒, and wettability techniques. SE is a highly surface-sensitive technique which enables detection of not only submonolayer coverage of a surface by adsorbed species 28,29 but also the surface roughness of its size smaller than the wavelength of light.…”

“…30 An ambient-type AFM does not require special care in sample preparation but has sufficient resolution for evaluating atomic-scale roughness. We thus use AFM to independently assess surface morphology changes that result from NH 4 OH etching and that enter into our optical modeling using SE data. We also use XPS to give an overview of the core-level XPS lines on the NH 4 OH-cleaned surfaces.…”

“…From this analysis, we obtain an apparent GaP oxide overlayer thickness of d ox ϳ 1.9 nm with an unbiased estimator of = 0.033. The three-layer analysis result for a sample treated in NH 4 OH solution for t = 2 s is shown in Fig. 3͑a͒ Fig.…”

Epitaxial lift-off process for gallium arsenide substrate reuse and flexible electronics

“…It has been proven that the GaAs surface becomes highly hydrophobic (like H-terminated surface that forms by dipping Si into HF) after it is dipped into HF or HCl 25,26 . The surface gallium atoms are passivated by fluorine or chlorine atoms and the surface arsenic atoms are possibly passivated by hydrogen atoms 25,[27][28][29] .…”