Vertical cavity surface emitting laser having strain reduced quantum wells

• US 8,451,875 B2
• Filed: 10/31/2006
• Issued: 05/28/2013
• 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: Johnson, Ralph H.
• Primary Examiner(s): Stultz, Jessica
• Assistant Examiner(s): King, Joshua
• Application Number:
  US11/554,754
• Publication Number:
  US 20070201525A1
• Time in Patent Office: 2,401 Days
• Field of Search: 372/43.01, 372/44.01
• US Class Current: 372/44.01
• 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
• CPC Class Codes: H01S 5/3095 Tunnel junction

Abstract

A VCSEL with nearly planar intracavity contact. A bottom DBR mirror is formed on a substrate. A first conduction layer region is formed on the bottom DBR mirror. An active layer, including quantum wells, is on the first conduction layer region. A trench is formed into the active layer region. The trench is formed in a wagon wheel configuration with spokes providing mechanical support for the active layer region. The trench is etched approximately to the first conduction layer region. Proton implants are provided in the wagon wheel and configured to render the spokes of the wagon wheel insulating. A nearly planar electrical contact is formed as an intracavity contact for connecting the bottom of the active region to a power supply. The nearly planar electrical contact is formed in and about the trench.

Claims

1. A VCSEL comprising:

a substrate;

an essentially undoped bottom DBR mirror disposed on the substrate;

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

an active layer region disposed on the first conduction layer region that contains one or more migration enhanced epitaxy layer regions before and between N-containing quantum wells each migration enhanced epitaxy layer region having at least one flattened layer under on a substrate side of a N-containing layer of the migration enhanced epitaxy layer region or a substrate side of the N-containing quantum well, wherein the quantum wells are InGaAsN quantum wells with Sb, wherein the nitrogen concentration is about 2% and the concentration of the In is less than about 28% and In and Sb together is less than or equal to about 28%;

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

a ramp layer region positioned between the periodically doped second donduction layer region and an aperture, the ramp layer region including a ramp of aluminum in a composition of the ramp layer region; and

a top mirror coupled to the second conduction layer region, wherein;

the aperture being above the quantum wells and below the periodically doped second conduction layer region and being defined by an oxidized AlGaAs layer;

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%; and

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

wherein the heavily doped layer of the periodically doped second conduction layer region, the ramp layer region, and the oxidized AlGaAs layer are within a single null of a standing wave of the VCSEL.

2. The VCSEL of claim 1, wherein the Indium (In) is about 26%.

3. The VCSEL as recited in claim 1, wherein the VCSEL is designed to operate at wavelengths above about 1260 nm.

4. The VCSEL as recited in claim 1, wherein the VCSEL is designed to operate at wavelengths above about 850 nm.

5. The VCSEL of claim 1, wherein the quantum wells are about In_0.26Ga_0.74As_0.96N_0.02Sb_0.02.

6. The VCSEL of claim 5, wherein the active region includes 4 quantum wells.

7. The VCSEL of claim 6, comprising barrier layers associated with the quantum wells, the barrier layers having N and/or Sb, and having one or more of the flattened layers that are devoid of N before and/or after and/or between the one or more N-containing barrier layers.

8. The VCSEL of claim 1, wherein the one or more migration enhanced epitaxy layer regions include one or more N-containing layers with one or more of the flattened layers that are devoid of N before and/or after and/or between the one or more N-containing layers.

9. The VCSEL of claim 8, wherein the one or more migration enhanced epitaxy layer regions include flattened layers formed from alternating single atomic layers of group III constituents and group V constituents.

10. The VCSEL of claim 9, wherein the single atomic layers are Ga or As.

11. The VCSEL of claim 9, wherein:

each quantum well thickness is approximately 50 Å

or less;

4 quantum wells are included in the active region; and

the quantum wells are about In_0.26Ga_0.74As_0.96N_0.02Sb_0.02.

12. The VCSEL of claim 11, substantially devoid of a quantum dot or 3-Dimensional growth effects.

13. The VCSEL of claim 1, wherein each flattened layer is devoid of N and on a substrate side of an N-containing layer or quantum well.

14. The VCSEL of claim 1, wherein the active region comprises N-containing layers interspersed with N-devoid layers associated with the quantum wells or quantum well barriers, wherein the N-devoid layers include single atomic layers of group III and group V constituents and are each flattened.

15. The VCSEL of claim 14, wherein the N-containing layers are deposited on N-devoid layers, the N-containing layers include an amount of In and/or Sb that creates a compressive strain between the N-containing layers and the flattened N-devoid layers, without relaxation, thereby decreasing the band gap energy.

16. The VCSEL of claim 14, wherein the quantum wells are about In_0.26Ga_0.74As_0.96N_0.02Sb_0.02.