Light emitting element and method of fabrication thereof

• US 6,611,003 B1
• Filed: 12/22/1999
• Issued: 08/26/2003
• Est. Priority Date: 06/29/1998
• Status: Expired due to Term

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Fujimoto, Hidetoshi, Hatakoshi, Genichi, Terauchi, Mamoru
• Primary Examiner(s): Wille, Douglas A.
• Application Number:
  US09/468,949
• Time in Patent Office: 1,343 Days
• Field of Search: 257/99, 257/95, 257/98, 372/43-46
• US Class Current: 257/98
• CPC Class Codes: B82Y 20/00 Nanooptics, e.g. quantum optics or photonic crystals
• CPC Class Codes: H01L 2224/4847 the connecting portion on the bonding area of the semiconductor or solid-state body being a wedge bond
• CPC Class Codes: H01L 2224/49107 on the semiconductor or solid-state body
• CPC Class Codes: H01L 33/10 with a light reflecting structure, e.g. semiconductor Bragg reflector
• CPC Class Codes: H01L 33/20 with a particular shape, e.g. curved or truncated substrate
• CPC Class Codes: H01L 33/46 Reflective coating, e.g. dielectric Bragg reflector
• CPC Class Codes: H01S 2301/16 Semiconductor lasers with special structural design to influence the modes, e.g. specific multimode
• CPC Class Codes: H01S 5/0202 Cleaving
• CPC Class Codes: H01S 5/028 Coatings ; Treatment of the laser facets, e.g. etching, passivation layers or reflecting layers
• CPC Class Codes: H01S 5/0286 Coatings with a reflectivity that is not constant over the facets, e.g. apertures
• CPC Class Codes: H01S 5/18308 having a special structure for lateral current or light confinement
• CPC Class Codes: H01S 5/18394 Apertures, e.g. defined by the shape of the upper electrode
• CPC Class Codes: H01S 5/34333 with a well layer based on Ga(In)N or Ga(In)P, e.g. blue laser

Abstract

This invention provides a light-emitting element that comprises a light-emitting portion made of a nitride semiconductor; and a first wavefront converter for converting the radiated shape of light that is emitted from the light-emitting portion into a radiated shape that is smaller than the wavelength thereof, and emitting the same as output light. In this case, the first wavefront converter has a small aperture of a diameter that is smaller than the wavelength of light that is emitted from the light-emitting portion. If the output light is made to comprise an evanescent wave that is emitted to the exterior through this small aperture, it is possible to obtain an extremely small light spot. This invention also relates to a surface-emitting type of light-emitting element comprising a multi-layered structure comprising a light-emitting layer; and a pair of electrodes for supplying a current to the light-emitting layer; wherein output light is emitted from a light-emitting surface on top of the multi-layered structure; and the pair of electrodes are recessed from the light-emitting surface to the light-emitting layer side. This makes it possible to bring the light-emitting surface extremely close to an object to be illuminated. The small aperture can be opened up in a self-aligning manner by using the light from the light-emitting portion. As a result, it is possible to provide a light-emitting element and a method of fabrication thereof that create beam characteristics that are suitable for use with an optical disc or the like.

Claims

1. A light-emitting element of a surface-emitting type, comprising:

a substrate having a first surface and a second surface, said substrate being transparent to light with a wavelength of λ

;

a diffraction grating lens overlying said first surface of said substrate;

a first conductive type semiconductor layer overlying said diffraction grating lens;

a light emitting layer formed on said first conductive type semiconductor layer and emitting light with a wavelength of λ

by current injection;

a second conductive type semiconductor layer formed on said light-emitting layer and having an electrode forming surface;

a wavefront converter of a material opaque to the light from said light-emitting layer, formed on said second surface of said substrate, and having a small aperture with a diameter smaller than a wavelength of the light, the light from said light-emitting layer passing through said small aperture to be emitted as an output light, said output light including an evanescent wave;

a first electrode formed on a surface of said first conductive type semiconductor layer on the side of said light-emitting layer, and electrically connected to said first conductive type semiconductor layer; and

a second electrode formed on said electrode forming surface of said second conductive type semiconductor layer,

said diffraction grating lens focusing light emitted from said light-emitting layer on said small aperture of said wavefront converter.

2. The light-emitting element as defined in claim 1, further comprising:

a first buffer layer formed on said first surface of said substrate, said diffraction grating lens being formed on said first buffer layer; and

a second buffer layer formed on said diffraction grating lens.

3. The light-emitting element as defined in claim 2, wherein said first buffer layer, said second buffer layer, said first conductive type semiconductor layer, said light-emitting layer, and said second conductive type semiconductor layer are formed of a nitride semiconductor.

4. The light-emitting element as defined in claim 3, wherein said substrate is a sapphire substrate.

6. The light-emitting element as defined in claim 1, wherein said light-emitting element is a vertical-cavity surface-emitting laser.

5. The light-emitting element as defined in clam 2, wherein said diffraction grating lens contains SiO₂.