Electromagnetic enhancement effect on the atomically abrupt heterojunction of Si/InAs heterostructured nanowires

Abstract

Semiconductor nanowires (NWs) present a great number of unique optical properties associated with their reduced dimension and internal structure. NWs are suitable for the fabrication of defect free Si/III-V heterostructures, allowing the combination of the properties of both Si and III-V compounds. We present here a study of the electromagnetic (EM) resonances on the atomically abrupt heterojunction of Si/InAs axially heterostructured NWs. We studied the electromagnetic response of Si/InAs heterojunctions sensed by means of Micro-Raman spectroscopy. These measurements reveal a high enhancement of the Si Raman signal when the incident laser beam is focused right on the Si/InAs interface. The experimental Raman observations are compared to finite element methods (FEM) simulations for the interaction of the focused laser beam with the heterostructured NW. The simulations explain why the enhancement is detected on the Si signal when illuminating the HJ and also provide a physical framework to understand the interaction between the incident

Composition, Optical Resonances, and Doping of InP/InGaP Nanowires for Tandem Solar Cells: a Micro-Raman Analysis

“…The few existing articles regarding Raman characterization of n-type doped InGaP suggest preferential coupling of the electron plasma oscillations to LO1 phonons. 29 , 44 Peak L1, recorded from the p-doped segments of the NW is in agreement with the data in references. 29 , 44 It has the symmetry of the LO phonon and appears between the LO1 and TOM peaks.…”

“…Upon fitting the spectra, one obtains a significant decrease of the LO1/LO2 intensity ratio in the p-doped sample, suggesting that the hole plasma oscillations mainly couple to the LO1 phonon mode of InGaP. The few existing articles regarding Raman characterization of n-type doped InGaP suggest preferential coupling of the electron plasma oscillations to LO1 phonons. , Peak L1, recorded from the p-doped segments of the NW is in agreement with the data in references. , It has the symmetry of the LO phonon and appears between the LO1 and TOM peaks. It appears closer to the TOM peak than in the epitaxial layers probably because of the higher hole concentration in the NWs.…”

“…It should be noted that the n + -InP side of the tunnel diode, with a length of 30–50 nm depending on the NW length, is silent in the Raman spectrum. The enhanced optical absorption at NW axial HJs was studied in previous articles. , It was shown that strong local optical resonances can take place at the HJ, mainly on one side of the HJ depending on the refractive index mismatch between the two sides of the HJ Figure a shows the calculated electromagnetic field distribution inside the NW under the excitation with the laser beam.…”

“… 13 , 43 It was shown that strong local optical resonances can take place at the HJ, mainly on one side of the HJ depending on the refractive index mismatch between the two sides of the HJ. 44 Figure 3 a shows the calculated electromagnetic field distribution inside the NW under the excitation with the laser beam. The electromagnetic field distribution was calculated by using COMSOL multiphysics.…”

Fourier transform study of the complex electric field induced on axially heterostructured nanowires

“…Recently, we have reported a significant local enhancement of the Raman signal at the heterojunction (HJ) of axially heterostructured Si/SiGe NWs [21,22] and Si/InAs NWs [23]. This is an interesting issue since the enhancement of the electromagnetic field at the HJ of NWs should provide an additional degree of freedom to engineer the photon absorption and scattering by semiconductor NWs, which should permit to operate photons over different optical resonances.…”