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Study of concentration‐dependent dielectric properties of n‐type GaAs using variable angle spectroscopic ellipsometry
Author(s) -
Snyder Paul G.,
Xiong YiMing
Publication year - 1992
Publication title -
surface and interface analysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.52
H-Index - 90
eISSN - 1096-9918
pISSN - 0142-2421
DOI - 10.1002/sia.740180208
Subject(s) - amplitude , overlayer , dielectric , ellipsometry , analytical chemistry (journal) , doping , spectral line , materials science , chemistry , molecular physics , optics , thin film , optoelectronics , physics , nanotechnology , chromatography , astronomy
Abstract The dielectric function ε spectra of Si‐doped n‐type GaAs crystals at room temperature (296 K) have been determined between 1.53 and 5.01 eV, using variable angle spectroscopic ellipsometry (VASE). Samples with carrier concentrations ranging from 4.6 × 10 17 to 3.3 × 10 18 cm −3 were measured. The effects of surface microscopic roughness, native oxide overlayer and the subsurface damage were mathematically removed with an appropriate multilayer model. The GaAs dielectric function spectra were modeled using the sum of seven harmonic oscillators, whose center energies, half‐widths and amplitudes were fitting parameters in the multilayer model. It was found that, as the doping level increased, the E 1 and E 1 + Δ 1 peak structures near 3 eV in the ε 2 spectrum broadened considerably more than the E 0 ′ and E 2 peak structures near 4.7 eV, while the amplitude of the E 1 peak decreased with respect to that of the E 1 + Δ 1 peak. Other effects due to doping were a shift of the ε 2 spectrum towards lower energies and a decrease in the amplitude of the E 2 peak.