Vertical cavity surface emitting laser having multiple top-side contacts

• US 20060072640A1
• Filed: 09/12/2005
• Published: 04/06/2006
• Est. Priority Date: 10/01/2004
• Status: Active Grant

• Current Assignee: II-VI Delaware, Inc. (Coherent Corp.)
• Original Assignee: Finisar Corporation (II-VI Incorporated)
• Inventors: Biard, James Robert, Penner, R. Scott, Fitzgerald, Colby, Johnson, Ralph H.
• Granted Patent: US 7,826,506 B2
• Time in Patent Office: Days
• US Class Current: 372/43.10
• CPC Class Codes: H01S 5/04252 characterised by the material
• CPC Class Codes: H01S 5/04257 having positive and negative electrodes on the same side of the substrate
• CPC Class Codes: H01S 5/18308 having a special structure for lateral current or light confinement
• CPC Class Codes: H01S 5/18311 using selective oxidation
• CPC Class Codes: H01S 5/1833 with more than one structure
• CPC Class Codes: H01S 5/18341 Intra-cavity contacts
• CPC Class Codes: H01S 5/18358 containing spacer layers to adjust the phase of the light wave in the cavity
• CPC Class Codes: H01S 5/305 characterised by the doping materials used in the laser structure

Abstract

A VCSEL with undoped mirrors. An essentially undoped bottom DBR mirror is formed on a substrate. A periodically doped first conduction layer region is formed on the bottom DBR mirror. The first conduction layer region is heavily doped at a location where the optical electric field is at about a minimum. An active layer, including quantum wells, is on the first conduction layer region. A periodically doped second conduction layer region is connected to the active layer. The second conduction layer region is heavily doped where the optical electric field is at a minimum. An aperture is formed in the epitaxial structure above the quantum wells. A top mirror coupled to the periodically doped second conduction layer region. The top mirror is essentially undoped and formed in a mesa structure. An oxide is formed around the mesa structure to protect the top mirror during wet oxidation processes.

Claims

1. A VCSEL comprising a substrate and an epitaxial structure, wherein the epitaxial structure comprises:

a bottom DBR mirror disposed on the substrate wherein the bottom mirror is essentially undoped;

a periodically doped first conduction layer region of a first conductivity type, the doped first conduction layer region coupled to the bottom DBR mirror, the doped first conduction layer region being heavily doped at a location where the optical electric field is at about a minimum;

an active layer disposed on the periodically doped first conduction layer region that contains quantum wells;

a periodically doped second conduction layer region of a second conductivity type, the doped second conduction layer region coupled to the active layer, the doped second conduction layer region being heavily doped at a location where the optical electric field is at about a minimum;

an aperture formed in the epitaxial structure above the quantum wells and below the second conduction layer region;

a top mirror coupled to the periodically doped second conduction layer region, wherein the top mirror is essentially undoped, the top mirror forming a mesa structure; and

a protective oxide layer surrounding the top mirror to protect at least a portion the top mirror from being oxidized during a wet oxidation step.

2. The VCSEL of claim 1, wherein the top mirror comprises alternating layers of GaAs and AlGaAs.

3. The VCSEL of claim 2, wherein the AlGaAs is 87.5%.

4. The VCSEL of claim 1, wherein the top mirror comprises alternating layers of GaAs and AlAs.

5. The VCSEL of claim 1, wherein the protective oxide layers has at least portions which are about 3λ

/8.

6. The VCSEL of claim 1, wherein a conduction layer region comprises layers that are doped at between about 5×

10¹⁹/cm³ to 1×

10²⁰/cm³ at about the minimum of the optical electric field and less than 1×

10¹⁸/cm³ away from the minimum of the optical electric field.

7. The VCSEL of claim 1, further comprising an intracavity contact coupled to the second conduction layer region.

8. The VCSEL of claim 7, wherein the intracavity contact comprises TiAu.

9. The VCSEL of claim 7, wherein the top mirror forms at least a portion of a mesa and the intracavity contact metal is coupled to the sides of the mesa.

10. The VCSEL of claim 1, further comprising a second intracavity contact coupled to the second conduction layer region.

11. The VCSEL of claim 1, wherein the VCSEL is designed to operated at a wavelength of at least 1260 nm.

12. A method of fabricating a VCSEL comprising:

forming an essentially undoped bottom mirror on a substrate wherein forming a bottom mirror comprises forming alternating layers of materials with different indices of refraction;

forming a first conduction layer region on the bottom mirror, wherein forming a first conduction layer region comprises doping portions of the first conduction layer region more heavily at a location where the optoelectronic energy is at about a minimum when the VCSEL is in use

forming an active layer that contains quantum wells on the first conduction layer region;

forming a second conduction layer region on the active layer, wherein forming a second conduction layer region comprises doping portions of the second conduction layer region more heavily at a location where the optoelectronic energy is at about a minimum when the VCSEL is in use;

forming a top mirror on the second conduction layer region such that the top mirror is essentially undoped and such that the top mirror forms a mesa structure; and

forming an oxide layer around the mesa structure to protect the top mirror from a wet oxidation step.

13. The method of claim 12, wherein forming a top mirror comprises forming alternating layers of AlAs and GaAs.

14. The method of claim 12, wherein forming an oxide layer around the mesa structure comprises depositing the oxide layer using plasma enhanced chemical vapor deposition.

15. The method of claim 12, further comprising:

forming a trench;

growing an aperture using a high temperature wet oxide from the trench edge.

16. The method of claim 15, wherein forming a trench comprises forming a trench in a wagon wheel structure with a plurality of spokes.

17. The method of claim 12, further comprising:

implanting ions to isolate a VCSEL from other VCSELs on a wafer;

forming a second intracavity contact on the second conduction layer region.

18. In a processing system for processing a wafer with an epitaxial structure including a bottom mirror, a first conduction layer, an active region a second conducting layer and a top mirror, a method of manufacturing a VCSEL comprising:

performing a first etch to form a mesa structure, wherein the mesa structure includes at least a portion of the top mirror;

depositing a photoresist layer to form an HF shield mask around at least a portion of the mesa structure;

performing an HF etch to expose a portion of the second conduction layer; and

forming an oxide layer around the mesa structure to protect the top mirror from a wet oxidation step.