In this paper, we present a thorough study of the characteristics of the surface modes that result from coupling between plasmon electronic oscillation modes, phonon modes, and electromagnetic modes. The Fourier transform of p-polarized reflectivity measurements were carried out on different 4 H-SiC epilayers differing in their free carrier concentration. The reflectivity measurements were performed with appropriate care to record reflectivity spectra averaged over a wide range of incidence angles. The complex infrared dielectric functions of the measured samples were determined by correcting the values obtained from the conventional Kramers-Kronig conversion technique with reference to Fresnel equations for reflectivity. The obtained dielectric functions were used to compute the effect of the free carrier concentration and the resulting plasmon electronic oscillation on the dispersion spectrum, lifetime, mean propagation length of the bulk, and surface plasmon-phonon-polariton modes. The effect of the fr...

Dependence of surface plasmon-phonon-polariton in 4 H-SiC on free carrier concentration

Procede de realisation d'un detecteur de neutrons et detecteur de neutrons

The present invention relates to a method for producing a device for detecting a flux of neutrons the parameters of which are comprised in predetermined ranges, characterised in that it comprises at least: one phase of determining parameters, comprising the following steps: - simulating the penetration of a flux of incident neutrons the parameters of which are comprised in said predetermined ranges through a modelled stack comprising in succession and in order at least: one first electrode (601); one substrate comprising: a first layer (100); and a second layer (400); and one second electrode (602); and - simulating at least one defect peak (801, 802) created in the first layer (100) by the vacancies and/or the ionisation of the particles generated by collisions between the neutrons of the flux of incident neutrons and the atoms of the second dopant species; and identifying the depth of the defect peak (801) closest the interface between the first and second layers (100, 400) of the modelled stack

Method for producing a neutron detector and neutron detector

A comparison is made between two kinds of Nitrogen implantations for the formation of thin n+p junctions in p-type Silicon Carbide (SiC) epitaxial layers. The standard beam ion implantations and PULSIONTM processes were performed at two distinct energies (700 eV and 7 keV) and the subsequent annealing was held at 1600°C in a resistive furnace specifically adapted to SiC material. Positron Annihilation Spectroscopy (PAS) and unpolarized infrared reflectivity (IR) measurements were carried out before and after the annealing, respecively. Despite the presence of deep vacancy clusters near the as-implanted sample surfaces, no extended defects were detected after the annealing. Plasma implanted samples prove to contain a lower point defect concentration than beam implanted samples. The concentration of these defects (resulting from plasma process) is higher in the plane parallel to the optical axis, which denotes an energy spreading alongside the dopant distribution.

Study of Defects Generated by Standard- and Plasma-Implantation of Nitrogen Atoms in 4H-SiC Epitaxial Layers

This paper deals with optical and electrical simulations of 4H-SiC UV-Photodetectors based on pn junctions. The simulations are performed under the UV light, with wavelengths varying between 200 nm and 300 nm. Under reverse bias, the simulation results point out the influence of surface patterns on the current density. The studied structures of the patterns consist in a semicircle with or without a flat surface. The patterned surfaces are parametrized according to the semicircle radius R and the flat surface length L. We show that the optical absorption strongly depends on these parameters, giving a maximum value whatever the wavelength with R = 100 nm and L = 0 nm (no flat surface). However, to optimise the carrier harvest, it is important for the space charge region to be situated in a zone where the optical generation is high. This study shows that the photodetector current density increases within three orders of magnitude (from 9x10-14 A.cm-2 to 3x10-10 A.cm-2), by using the specific surface pattern given above.

Stephane Biondo

Papers

Study of Defects Generated by Standard- and Plasma-Implantation of Nitrogen Atoms in 4H-SiC Epitaxial Layers

Full Simulation Study of UV Photodetectors Based on Pn Junctions in Silicon Carbide