Raman scattering measurements of decreased barrier heights in GaAs following surface chemical passivation

Abstract

We present Raman scattering data from GaAs samples whose surfaces had been treated with thin films of sodium sulfide nonahydride (Na2S⋅9H2O). Raman scattering provides a quantitative, contactless means of measuring the reduced barrier height associated with decreased density of GaAs surface states. For GaAs samples doped at levels of n≊1018 cm−3, the barrier height is reduced to 0.48±0.10 eV.

Passivation at semiconductor/electrolyte interface: Role of adsorbate solvation and reactivity in surface atomic and electronic structure modification of III–V semiconductor

“…The corresponding surface depletion layer width for these semiconductors were d n0 = 33.6 nm and d p0 = 26.9 nm, respectively, i.e., considerably lower than the penetration depth of laser excitation into GaAs. The depletion layer width of semiconductor after adsorption of HS -ions was estimated on the basis of the balance between intensities of L À (scattering from the coupled phonon-plasmon mode) and LO peaks in Raman spectra [31,32].…”

“…The difference in atomic structure should result in the difference in the electronic properties of the GaAs(1 0 0) surfaces obtained after adsorption of HS -ions from different solvents. These values were calculated from the experimental Raman spectra according to the procedure described in [31,32]. The data are plotted against the reciprocal dielectric constant value of the solvent.…”

Near-surface electronic structure in GaAs (100) modified with self-assembled monolayers of octadecylthiol

“…These spectra compare favorably to previous Raman studies of inorganic sulfide-passivated GaAs. 22,23 The dashed lines represent the fit to the theoretical lineshapes of the LO and L Ϫ modes. The LO peak near 290 cm Ϫ1 closely approximates a Lorentzian line shape as predicted by theory, however the peak is fit to a Voigt profile to account for the instrument Gaussian contribution of the spectrometer.…”

Raman scattering characterization of the crystalline qualities of ZnSe films grown on S-passivated GaAs(100) substrates

“…2,21 Since ZnSe material is almost transparent to 488 nm radiation, the Raman signals of GaAs substrates can be observed in Fig. 1.…”

“…For our samples C 1 and C 2 with n ϩ -type doping concentration of 1.3ϫ10 18 cm Ϫ3 , the width of surface depletion layer ␦ is smaller than the penetration depth D ͑about 80 nm͒ of the light of 488 nm, 22 thus only the uncoupled LO phonon will be excited in the surface depletion region and the LO coupled phonon-plasmon peak L Ϫ comes from the GaAs bulk. In this case, the intensity I͑LO͒ of LO phonon is given by 21,23 I͑LO͒ϭI 0 ͑LO͓͒1Ϫexp͑Ϫ2␦/D ͔͒, ͑1͒…”