Carbon doped GaAsSb suitable for use in tunnel junctions of long-wavelength VCSELs

• US 7,295,586 B2
• Filed: 02/21/2002
• Issued: 11/13/2007
• Est. Priority Date: 02/21/2002
• Status: Expired due to Fees

• Current Assignee: II-VI Delaware, Inc. (Coherent Corp.)
• Original Assignee: Finisar Corporation (II-VI Incorporated)
• Inventors: Kwon, Hoki
• Primary Examiner(s): NGUYEN, DUNG T
• Application Number:
  US10/078,473
• Publication Number:
  US 20030156610A1
• Time in Patent Office: 2,091 Days
• Field of Search: 372/43, 372/45, 372/46
• US Class Current: 372/45.01
• CPC Class Codes: H01L 21/02392 Phosphides
• CPC Class Codes: H01L 21/02463 Arsenides
• CPC Class Codes: H01L 21/02507 Alternating layers, e.g. superlattice
• CPC Class Codes: H01L 21/02543 Phosphides
• CPC Class Codes: H01L 21/02546 Arsenides
• CPC Class Codes: H01L 21/02549 Antimonides
• CPC Class Codes: H01L 21/02579 P-type
• CPC Class Codes: H01L 21/0262 Reduction or decomposition of gaseous compounds, e.g. CVD
• CPC Class Codes: H01L 29/66151 Tunnel diodes group 13/15 resonant tunneling diodes H01L29/66219
• CPC Class Codes: H01L 29/88 Tunnel-effect diodes
• CPC Class Codes: H01S 2301/173 The laser chip comprising special buffer layers, e.g. dislocation prevention or reduction
• CPC Class Codes: H01S 2304/04 MOCVD or MOVPE
• CPC Class Codes: H01S 5/18308 having a special structure for lateral current or light confinement
• CPC Class Codes: H01S 5/18358 containing spacer layers to adjust the phase of the light wave in the cavity
• CPC Class Codes: H01S 5/3054 p-doping
• CPC Class Codes: H01S 5/3095 Tunnel junction
• CPC Class Codes: H01S 5/3215 graded composition cladding layers

Abstract

GaAs_(1−x)Sb_x layers are grown by MOCVD. For lattice matching with InP, x is set to 0.5, while beneficial alternatives include setting x to 0.23, 0.3, and 0.4. During MOVCD, TMGa (or TEGa), TMSb, and AsH₃ (or TBAs) are used to fabricate the GaAs_{(1−x )}Sb_x layer. Beneficially, the GaAs_(1−x)Sbx layer'"'"'s composition is controlled by the ratio of As to Sb. The MOCVD growth temperature is between 500° C. and 650° C. The GaAs_(1−x)Sb_x layer is beneficially doped using CCl₄ or CBr₄. A heavily doped GaAs_(1−x)Sb_x layer can be used to form a tunnel junction with n-doped layers of InP, AlInAs, or with lower bandgap materials such as AlInGaAs or InGaAsP. Such tunnel junctions are useful for producing long wavelength VCSELs.

Claims

1. A method of fabricating a vertical cavity surface emitting laser (VCSEL) with a tunnel junction, the method comprising:

locating a substrate in an MOCVD chamber;

forming an active region over the substrate, the active region having a plurality of quantum wells;

setting a temperature of the MOCVD chamber between 500°

C. and 650°

C.; and

growing a tunnel junction including GaAs<sub>(1−

X)</sub>Sb_x over the active region using an MOCVD process in which a source of Ga, a source of Sb, and a source of As are present.

2. The method according to claim 1, wherein x has a value corresponding to a ratio of As to Sb.

3. The method according to claim 2, wherein the value of x is 0.5.

4. The method according to claim 2, wherein the value of x is less than 0.5.

5. The method according to claim 1, wherein the source of Ga is TMGa or TEGa, and the source of Sb is TMSb.

6. The method according to claim 1, wherein the source of As is AsH₃ or TBAs.

7. The method according to claim 1, further including carbon doping the GaAs₍₁₋

x)Sbx_x using CCl₄ or CBr₄.

8. A tunnel junction comprising:

a p-doped GaAs<sub>(1−

x)</sub>Sb_x layer, wherein x is set at a value such that the p-doped GaAs<sub>(1−

x)</sub>Sb_x layer is substantially lattice matched with an InP based active region and has a strain less than 1.95%; and

an n-doped layer of InP, AlInAs, AlInGaAs, or InGaAsP, wherein the n-doped layer is doped with a concentration greater than 5×

10¹⁹ cm<sup>−

3</sup>.

9. The tunnel junction according to claim 8, wherein the p-doped GaAs₍₁₋

x)Sb_x layer is doped with carbon with a concentration greater than 1×

1¹⁹ cm<sup>−

3</sup>.

10. The tunnel junction according to claim 8, wherein the GaAs₍₁₋

x)Sb_x layer is doped with a concentration greater than 5×

10¹⁹ cm<sup>−

3</sup>, and wherein the tunnel junction is less than about 10 nanometers thick.

11. The tunnel junction according to claim 8, wherein the n-doped layer is InP, and wherein x has a value of 0.5.

12. A vertical cavity surface emitting laser, comprising:

an active region having a plurality of quantum wells, and

a tunnel junction over said active region, wherein said tunnel junction includes a GaAs<sub>(1−

x)</sub>Sb_x layer.

13. The vertical cavity surface emitting laser according to claim 12, further including an n-type bottom spacer adjacent the active region, and an n-type bottom DBR adjacent the n-type bottom spacer.

14. The vertical cavity surface emitting laser according to claim 12, further including an n-type top spacer adjacent the tunnel junction and an n-type top DBR adjacent the n-type top spacer.

15. The vertical cavity surface emitting laser according to claim 12, wherein the GaAs₍₁₋

x)Sb_x layer is grown by MOCVD.

16. The vertical cavity surface emitting laser according to claim 12, wherein the GaAs₍₁₋

x)Sb_x layer is doped with carbon with a concentration greater than 5×

10¹⁹ cm<sup>−

3</sup>.

17. The vertical cavity surface emitting laser according to claim 12, wherein said active region includes InGaAsP or AlInGaAs.

18. The vertical cavity surface emitting laser according to claim 17, wherein said tunnel junction includes an n-type InP layer.

19. The vertical cavity surface emitting laser according to claim 12, wherein x is 0.5.

20. The vertical cavity surface emitting laser according to claim 12, wherein the tunnel junction has a thickness of less than about 10 nm.