Distribution of free carriers near heavily-doped epitaxial surfaces of n-type Ge(100) upon HF and HCl treatments

S J Park,L Bolotov,N Uchida,T Tada

doi:10.1063/1.4934673

S J Park, L Bolotov + Show 2 more

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Carrier distributions near n-type epitaxially-grown Ge(100) surfaces with high impurity concentrations (1 × 1020 cm−3) were studied using high resolution electron energy loss spectroscopy (HREELS) upon surface treatments in aqueous solutions of HF and HCl. After surface treatments with HCl and HF, the molecular vibration modes distinctly showed either chloride or hydride terminations of Ge surfaces with negligible oxidation. The free-carrier concentration profile was inferred from the conduction band plasmon measurements as a function of the incident electron energies employing a dielectric theory simulation with a 4-layer structure and an effective electron mass of 0.02m0. A carrier-free layer of 40 and 24 Å were derived for HCl- and HF-treated Ge(100), respectively. The surface band bending was estimated to be 0.32 eV for HF-treated Ge. HCl-treated Ge surfaces showed a band bending of 0.91 eV attributed to the strong effect of the surface Cl-Ge dipole.

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Distribution of free carriers near heavilydoped epitaxial surfaces of n-type Ge(100) upon HF and HCl treatments
We compared passivating surface layers and free-carrier distributions induced by different surface treatments for epitaxial n-type Ge(100) (200 nm thick) grown on intrinsic Ge/Si substrate using high resolution electron energy loss spectroscopy (HREELS)
The electric potential on HCl-treated Ge(100) surfaces was derived from the contact potential difference (CPD) voltage measured in the Kelvin mode by multimode scanning probe microscopy (MSPM) in UHV.[19,20]

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Distribution of free carriers near heavilydoped epitaxial surfaces of n-type Ge(100) upon HF and HCl treatments. Carrier distributions near n-type epitaxially-grown Ge(100) surfaces with high impurity concentrations (1 × 1020 cm−3) were studied using high resolution electron energy loss spectroscopy (HREELS) upon surface treatments in aqueous solutions of HF and HCl. After surface treatments with HCl and HF, the molecular vibration modes distinctly showed either chloride or hydride terminations of Ge surfaces with negligible oxidation.

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