Nitride-based laser diode with AlGaN waveguide/cladding layer

• US 20040184496A1
• Filed: 03/20/2003
• Published: 09/23/2004
• Est. Priority Date: 03/20/2003
• Status: Active Grant

• Current Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Original Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Inventors: Bour, David P., Romano, Linda T., Van de Walle, Christian G., Kneissl, Michael A.
• Granted Patent: US 7,123,637 B2
• Time in Patent Office: Days
• US Class Current: 372/45
• CPC Class Codes: B82Y 20/00 Nanooptics, e.g. quantum optics or photonic crystals
• CPC Class Codes: H01S 5/0213 Sapphire, quartz or diamond based substrates
• CPC Class Codes: H01S 5/2009 by using electron barrier layers
• CPC Class Codes: H01S 5/2205 comprising special burying or current confinement layers
• CPC Class Codes: H01S 5/2231 with inner confining structure only between the active layer and the upper electrode
• CPC Class Codes: H01S 5/3213 asymmetric clading layers
• CPC Class Codes: H01S 5/34333 with a well layer based on Ga(In)N or Ga(In)P, e.g. blue laser

Abstract

A nitride-based laser diode structure utilizing a single GaN:Mg waveguide/cladding layer, in place of separate GaN:Mg waveguide and AlGaN:Mg cladding layers used in conventional nitride-based laser diode structures. When formed using an optimal thickness, the GaN:Mg layer produces an optical confinement that is comparable to or better than conventional structures. A thin AlGaN tunnel barrier layer is provided between the multiple quantum well and a lower portion of the GaN:Mg waveguide layer, which suppresses electron leakage without any significant decrease in optical confinement. A split-metal electrode is formed on the GaN:Mg upper waveguide structure to avoid absorption losses in the upper electrode metal. A pair of AlGaN:Si current blocking layer sections are located below the split-metal electrode sections, and separated by a gap located over the active region of the multiple quantum well.

Claims

1. A nitride-based laser diode structure comprising:

a quantum well region;

a waveguide/cladding layer formed over the quantum well region; and

a metal electrode formed on an upper surface of the waveguide/cladding layer,

wherein the waveguide/cladding layer consists essentially of p-doped Gallium-Nitride (GaN).

2. The nitride-based laser diode structure according to claim 1,

wherein the quantum well region comprises alternating layers of Indium-Gallium-Nitride (InGaN) and GaN, and

wherein the waveguide/cladding layer has a thickness in the range of approximately 100 and 1000 nm, and comprises GaN doped with Magnesium.

3. The nitride-based laser diode structure according to claim 2, wherein the waveguide/cladding layer has a thickness of approximately 200 nm.

4. The nitride-based laser diode structure according to claim 3, further comprising a tunnel barrier layer formed between the quantum well region and the waveguide/cladding layer.

5. The nitride-based laser diode structure according to claim 4,

wherein the tunnel barrier layer comprises Aluminum-Gallium-Nitride doped with Magnesium (AlGaN:

Mg),

wherein the amount of Aluminum in the tunnel barrier layer is in the range of 5 and 30% (mole fraction), and

wherein the tunnel barrier layer and has a thickness in the range of 5 to approximately 50 nm.

6. The nitride-based laser diode structure according to claim 5, wherein the quantum well region includes an upper GaN layer formed over an uppermost InGaN quantum well layer, wherein the tunnel barrier layer is formed on the upper GaN layer, and wherein the waveguide/cladding layer is formed on the tunnel barrier layer.

7. The nitride-based laser diode structure according to claim 4, wherein the metal electrode comprises a split-gate arrangement including first and second flat portions formed on the upper surface of the waveguide/cladding layer such that a central section of the waveguide/cladding layer located between the first and second portions has an upper surface portion that is not contacted by the metal electrode, wherein the central section is located over an active region of the quantum well region.

8. The nitride-based laser diode structure according to claim 7, wherein the metal electrode further comprises a bridge portion connected between the first and second flat portions and extending over the central section of the waveguide/cladding layer such that a gap region is formed between the upper surface portion of the central section and a lower surface of the bridge portion.

9. The nitride-based laser diode structure according to claim 8, wherein the gap region comprises a dielectric material.

10. The nitride-based laser diode structure according to claim 7, further comprising a current blocking structure located inside the waveguide/cladding layer, wherein the current blocking structure includes first and second portions respectively located below the first and second flat portions of the metal electrode, and wherein the first and second portions of the current blocking structure are separated by the central section of the waveguide/cladding layer.

11. The nitride-based laser diode structure according to claim 10, wherein the current blocking structure comprises at least one of Aluminum-Gallium-Nitride doped with Silicon (AlGaN:

Si), Silicon-Dioxide (SiO2), Gallium-Nitride doped with Silicon (GaN;

Si), AlN, Si₃N₄, and Si_xO_yN_z.

12. A nitride-based laser diode structure comprising:

a quantum well region;

a tunnel barrier layer formed on the quantum well region;

a waveguide/cladding layer formed over the tunnel barrier layer; and

a metal electrode formed on an upper surface of the cladding layer,

wherein the tunnel barrier layer comprises Aluminum-Gallium-Nitride doped with Magnesium (AlGaN;

Mg), and

wherein waveguide/cladding layer consists essentially of p-doped Gallium-Nitride (GaN).

13. The nitride-based laser diode structure according to claim 12, wherein the amount of Aluminum in the tunnel barrier layer is in the range of 10 to 30% (mole fraction).

14. The nitride-based laser diode structure according to claim 12, wherein the tunnel barrier layer and has a thickness in the range of 5 to approximately 50 nm.

15. The nitride-based laser diode structure according to claim 12, wherein the metal electrode comprises a split-gate arrangement including first and second flat portions formed on the upper surface of the waveguide/cladding layer such that a central section of the waveguide/cladding layer located between the first and second portions has an upper surface portion that is not contacted by the metal electrode, wherein the central section is located over an active region of the quantum well region.

16. The nitride-based laser diode structure according to claim 15, wherein the metal electrode further comprises a bridge portion connected between the first and second flat portions and extending over the central section of the waveguide/cladding layer such that a gap region is formed between the upper surface portion of the central section and a lower surface of the bridge portion.

17. The nitride-based laser diode structure according to claim 16, wherein the gap region comprises a dielectric material.

18. A nitride-based laser diode structure comprising:

a quantum well region;

a waveguide/cladding layer formed over the quantum well region; and

a metal electrode formed on an upper surface of the waveguide/cladding layer,

wherein waveguide/cladding layer consists essentially of p-doped Gallium-Nitride (GaN), and

wherein the metal electrode comprises a split-gate arrangement including first and second flat portions formed on the upper surface of the waveguide/cladding layer such that a central section of the waveguide/cladding layer located between the first and second portions has an upper surface portion that is not contacted by the metal electrode, and

wherein the central section of the waveguide/cladding layer is located over an active region of the quantum well region.

19. The nitride-based laser diode structure according to claim 18, wherein the metal electrode further comprises a bridge portion connected between the first and second flat portions and extending over the central section of the waveguide/cladding layer such that a gap region is formed between the upper surface portion of the central section and a lower surface of the bridge portion.

20. The nitride-based laser diode structure according to claim 19, further comprising a current blocking structure located inside the waveguide/cladding layer, wherein the current blocking structure includes first and second portions respectively located below the first and second flat portions of the metal electrode, and wherein the first and second portions of the current blocking structure are separated by the central section of the waveguide/cladding layer.

21. The nitride-based laser diode structure according to claim 20, wherein the current blocking structure comprises at least one of Aluminum-Gallium-Nitride doped with Silicon (AlGaN:

Si), Silicon-Dioxide (SiO2), and Gallium-Nitride doped with Silicon (GaN;

Si), AlN, Si₃N₄, and Si_xO_yN_z.