Ab initio Theory of Second Harmonic Generation from Semiconductor Surfaces and Interfaces

Abstract

Predictions of second harmonic generation (SHG) from semiconductor surfaces and interfaces, based on first principles evaluation of eigen-value and eigen-vector problems using full potential linearized augmented plane wave (FLAPW) and ab initio pseudopotential (PP) approaches, are discussed. Effects of rehybridization of atomic bonds and electric field induced second harmonic (EFISH) response are considered. Strong contributions to the SHG efficiency of electron excitations from surface atom orbitals are demonstrated for Si(001) and GaN(0001) surfaces and the Ge/Si(001) interface. The predicted spectroscopic SHG results are discussed in comparison with experiment.

Characterization of chemisorption on porous silicon by sum frequency generation

“…Porous silicon was formed using stain etching with either a 2:1:2 by volume HF: HNO 3 : H 2 O solution or a solution with 1.6 g of FeCl 3 in 20 ml of 48% HF [12] . Samples are oriented such that φ, the angle between the [100] direction and the plane of incidence, is 90°.…”

“…Optical absorption spectra were calculated within the random phase approximation (RPA) approach [12] according to…”

“…Ab initio studies [10][11][12] have been instrumental in developing an understanding of SHG from clean and adsorbate-covered Si surfaces. The signal arises from a combination of bulk and surface contributions to the second-order nonlinear susceptibility tensor χ (2) and the tensor elements that contribute to the signal are determined by the substrate symmetry, the polarization of the incident excitation beams, and the polarization of the signal.…”

Optical Second Harmonic Generation in Semiconductor Nanostructures

“…As stated before SHG is extremely sensitive to the surfaces in cubic materials [25][26][27]. One of the reasons for that is the evidence that in centrosymmetric crystals the SHG response is forbidden by symmetry in bulk but allowed on the surface where the local symmetry is lower [25].…”

“…Due to the high value of Si-O bond energy corresponding contributions are located in far ultraviolet region. The SHG response from the Si-SiO 2 interface located mostly in visible and near-UV regions is attributed to the distorted host atomic bonds [25,30,43]. From the data presented in Figure 9 one can immediately extract features related to the oxygen.…”