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EP-4595173-B1 - SILICON PHOTONIC CRYSTAL

EP4595173B1EP 4595173 B1EP4595173 B1EP 4595173B1EP-4595173-B1

Inventors

  • CONOCI, SABRINA
  • IRRERA, Alessia
  • LEONARDI, Antonio Alessio
  • SPINELLA, CORRADO ROSARIO

Dates

Publication Date
20260513
Application Date
20231002

Claims (10)

  1. Silicon photonic crystal (10; 10'; 10") comprising periodic silicon structures (12) contiguous with voids (14), surrounding a silicon resonant cavity (16), characterized in that the resonant cavity (16) consists of nanowires (18) entirely made of silicon with uniform doping, said nanowires acting as active medium of the photonic crystal.
  2. Photonic crystal according to claim 1, wherein the silicon structures (12) consist of silicon nanowires (18).
  3. Photonic crystal according to claim 2 or 3, wherein the silicon nanowires (18) have a density of at least 10 11 nanowires/cm 2 .
  4. Photonic crystal according to any one of the preceding claims, wherein the silicon nanowires (18) have a diameter between 4 and 12 nanometers.
  5. Photonic crystal according to any one of the preceding claims, wherein the silicon nanowires (18) have a length between tens of nanometers and hundreds of microns.
  6. Photonic crystal according to any one of the preceding claims, further comprising rare earths and/or luminescent dyes (20) integrated between the silicon nanowires (18).
  7. Method of manufacturing a silicon photonic crystal (10; 10'; 10") according to any one of the preceding claims, the method comprising the steps of: - providing a base silicon photonic crystal (30'; 30"), comprising periodic silicon structures (12) contiguous with voids (14) and a silicon cavity (16), - obtaining, in said cavity (16), a plurality of silicon nanowires (18) entirely made of silicon with uniform doping, wherein the silicon nanowires (18) are made by subjecting said silicon cavity (16) to metal-assisted chemical etching with the use of thin percolative layers of gold (40) as metal catalyst.
  8. Method according to claim 7, further comprising the step of: - obtaining a plurality of silicon nanowires (18) in each of said periodic silicon structures (12), wherein the silicon nanowires (18) are made by subjecting said periodic silicon structures (12) to metal-assisted chemical etching with the use of thin percolative layers of gold (40) as metal catalyst.
  9. Method according to claim 7 or 8, wherein said step of obtaining a plurality of silicon nanowires (18) provides, before performing the metal-assisted chemical etching, for: - applying a resist (38) on the base photonic crystal (30'; 30"), - creating a mask of resist (38) that leaves uncovered only parts (16; 12, 16) that are to be subjected to metal-assisted chemical etching, - depositing percolative layers of gold (40), - removing the resist (38) so that percolative layers of gold (40) remain only on parts (16; 12, 16) that are to be subjected to metal-assisted chemical etching.
  10. Method according to any one of claims 7 to 9, further comprising the step of integrating the pluralities of silicon nanowires (18) with rare earths and/or luminescent dyes (20).

Description

Technical Field The present invention relates to a silicon photonic crystal for the enhancement and lasing of the silicon emission. The invention further relates to a method of manufacturing such photonic crystal. Background Art Silicon is an indirect bandgap semiconductor with negligible light emission at room temperature. Many studies have focused on the realization of various nanostructures or the engineering of implants or defects to achieve efficient roomtemperature emission from silicon. However, efficient lasing has not yet been observed. The importance of Auger phenomena for high fluences as well as engineering difficulties in suppressing the presence of non-radiative phenomena are among the main critical issues for silicon in the application as a light source at room temperature. Furthermore, the dimensions required to achieve quantum confinement in silicon have often been prohibitive for many manufacturing techniques and complex to realize for others. Among the various nanostructures, nanowires stand out due to their robustness and ease of integration with flat fabrication technology such as that required by microelectronics and silicon photonics. In this case, nanowires with diameters below 15 nm are required in order to observe light emission at room temperature by quantum confinement. EP 1804350 A1 discloses a semiconductor laser that is based on semiconducting elongate nanostructures and that may be fabricated on a silicon-compatible substrate. The structure comprises semiconductive elongate nanostructures that are parallel to one another and that contain a double-heterostructure, which forms the active region of the laser. The semiconducting elongate nanostructures are positioned in a periodic two-dimensional array such that the ensemble of nanowires forms a photonic crystal laser system. At both ends of the elongate nanostructures, there is an electrical contact, which is used to control the lasing action of the system. The fabrication of such a structure on a silicon-compatible substrate is realized by the possibility to grow crystalline elongate nanostructures on a substrate that has a different crystal configuration and lattice constant from the elongate nanostructures. However, there are no known large-scale manufacturing techniques that would allow the realization of high densities of nanowires with such small dimensions (below 15 nm), having quantum confinement effects and a vertically aligned structure, whereby no photonic crystal capable of amplifying the emission of silicon nanowires and achieving lasing has ever been realized. At present, silicon photonics is therefore not based on the use of silicon nanowires but on the integration of other active elements as light emitters into the silicon or on the use of external sources coupled to silicon via waveguides or optical fiber. The realization of silicon photonic crystals therefore involves the introduction of other materials whose luminescence can be selected and amplified by the engineering of the crystal and the resonant cavity of the crystal. Due to the poor light emission of silicon at room temperature, a device for lasing the light emission of silicon is absent. There is therefore the need for a silicon photonic crystal that is efficient and can increase lasing. An object of the invention is to provide a silicon photonic crystal that meets the aforesaid need. Another object of the invention is to provide a silicon photonic crystal that can be easily manufactured. A further object of the invention is to provide a silicon photonic crystal in which the wavelength of the emitted light can be shifted from the visible to the infrared region. These and other objects are achieved by the silicon photonic crystal as claimed in the appended claims. Summary of Invention The silicon photonic crystal for the enhancement and lasing of the silicon emission according to the invention comprises periodic silicon structures contiguous with voids, surrounding a silicon resonant cavity consisting of silicon nanowires with uniform doping, which can be either an n-type doping or a p-type doping. The active medium is therefore represented by the aforementioned resonant cavity nanowires in their entirety and the light emission is due to quantum confinement along the entire length of the nanowires. The active medium of the photonic crystal according to the invention therefore does not comprise heterojunctions. Optionally, the silicon structures of the photonic crystal also consist of silicon nanowires. The silicon nanowires have a density of at least 1011 nanowires/cm2, more preferably of approximately 1012 nanowires/cm2, a diameter between 4 and 12 nm and a length between tens of nanometers and hundreds of microns. The silicon nanowires in their entirety constitute the active medium of the photonic crystal, i.e., the material that emits light. The photonic crystal as described above emits light at about 700 nm at room temperature. Optionally, the photon