Vertical cavity surface emitting laser having multiple top-side contacts

• US 7,826,506 B2
• Filed: 09/12/2005
• Issued: 11/02/2010
• 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.
• Primary Examiner(s): Harvey; Minsun
• Assistant Examiner(s): King; Joshua
• Application Number:
  US11/224,615
• Publication Number:
  US 20060072640A1
• Time in Patent Office: 1,877 Days
• Field of Search: 372/46.013
• US Class Current: 372/46.013
• 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 including a heavily doped layer 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 including a heavily doped layer 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, wherein the aperture is defined by an oxidized AlGaAs layer;

a ramp layer positioned between the aperture and the second conduction layer region, the ramp layer including a ramp of aluminum in a composition of the ramp layer,

wherein the ramp layer, the heavily doped layer and the oxidized AlGaAs layer are within a single null of a standing wave of the VCSEL;

a top mirror coupled to the periodically doped second conduction layer region, wherein the top mirror is essentially undoped and includes a plurality of layers of AlGaAs having an aluminum content in a range from 70% to 100%, 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 1, further comprising a ramp layer, the ramp layer including AlGaAs where the aluminum content ramps between at least 50% and 71%.

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 layer has at least a portion which is about 3 λ

/8.

6. The VCSEL of claim 1, wherein the first and/or the second 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 first conduction layer region.

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

12. A VCSEL as in claim 1, wherein the protective oxide layer is a layer of silicon dioxide surrounding the AlGaAs layers.

13. A VCSEL as in claim 1, wherein the oxidized layer is less than 30 nm.

14. A VCSEL as in claim 1, wherein the second conduction layer region is less than 40 nm.