System and method using migration enhanced epitaxy for flattening active layers and the mechanical stabilization of quantum wells associated with vertical cavity surface emitting lasers

• US 20030219917A1
• Filed: 01/27/2003
• Published: 11/27/2003
• Est. Priority Date: 12/21/1998
• Status: Abandoned Application

• Current Assignee: II-VI Delaware, Inc. (Coherent Corp.)
• Original Assignee: II-VI Delaware, Inc. (Coherent Corp.)
• Inventors: Johnson, Ralph H., Blasingame, Virgil J.
• Application Number:
  US10/352,293
• Publication Number:
  US 20030219917A1
• Time in Patent Office: Days
• US Class Current: 438/22
• CPC Class Codes: B82Y 20/00 Nanooptics, e.g. quantum optics or photonic crystals
• CPC Class Codes: H01L 33/007 comprising nitride compounds
• CPC Class Codes: H01S 2302/00 Amplification / lasing wavelength
• CPC Class Codes: H01S 5/18308 having a special structure for lateral current or light confinement
• CPC Class Codes: H01S 5/3201 incorporating bulkstrain effects, e.g. strain compensation, strain related to polarisation
• CPC Class Codes: H01S 5/32358 containing very small amounts, usually less than 1%, of an additional III or V compound to decrease the bandgap strongly in a non-linear way by the bowing effect
• CPC Class Codes: H01S 5/32366 (In)GaAs with small amount of N
• CPC Class Codes: H01S 5/34 comprising quantum well or superlattice structures, e.g. single quantum well [SQW] lasers, multiple quantum well [MQW] lasers or graded index separate confinement heterostructure [GRINSCH] lasers H01S5/36 takes precedence
• CPC Class Codes: H01S 5/3403 having a strained layer structure in which the strain performs a special function, e.g. general strain effects, strain versus polarisation
• CPC Class Codes: H01S 5/3406 including strain compensation
• CPC Class Codes: H01S 5/34306 emitting light at a wavelength longer than 1000nm, e.g. InP based 1300 and 1500nm lasers
• CPC Class Codes: H01S 5/34313 with a well layer having only As as V-compound, e.g. AlGaAs, InGaAs
• CPC Class Codes: H01S 5/34346 characterised by the materials of the barrier layers
• CPC Class Codes: H01S 5/34353 based on (AI)GaAs

Abstract

Methods and Systems producing flattening layers associated with nitrogen-containing quantum wells and to prevent 3-D growth of nitrogen containing layers using high As fluxes. MEE (Migration Enhanced Epitaxy) is used to flatten layers and enhance smoothness of quantum wells interfaces and to achieve narrowing of the spectrum of light emitted from nitrogen containing quantum wells. MEE is performed by alternately depositing single atomic layers of group III and V before, and/or after, and/or in-between quantum wells. Where GaAs is used, the process can be accomplished by alternately opening and closing Ga and As shutters in an MBE system, while preventing both from being open at the same time. Where nitrogen is used, the system incorporates a mechanical means of preventing nitrogen from entering the MBE processing chamber, such as a gate valve. The gate valve allows the nitrogen source to be completely cut-off from the chamber during non-nitrogen processing steps to achieve the flattening layers described herein. In at least nitrogen containing layers, 3-dimensional growth is also reduced by using high arsenic fluxes, and by using substantially As4 as the main constituent of the arsenic flux.

Claims

1. A method for developing an active region containing nitrogen, said method comprising the steps of:

growing at least one nitrogen-free layer by alternately depositing single atomic layers of group III constituents and group V constituents without nitrogen being present, wherein said at least one nitrogen-free layer is substantially flat and suitable for growing layers of semiconductor material containing nitrogen; and

growing at least one nitrogen-containing layer on or near said nitrogen-free layer.

2. The method of claim 1 wherein said group III and group V constituents include Ga and As.

3. The method of claim 1 wherein said nitrogen-containing layers comprise at least one quantum well.

4. The method of claim 3 further comprising the step of providing an arsenic beam equivalent pressure greater than about 1.1e-5 torr during growth of said nitrogen-containing layers.

5. The method of claim 3 further comprising the step of providing an arsenic beam equivalent pressure greater than about 1.64e-5 torr during growth of said nitrogen-containing layers.

6. The method of claim 3 where an arsenic flux is created during growth of nitrogen-containing layers and comprises predominantly As₄.

7. The method of claim 1 wherein said nitrogen-containing layers comprise a plurality of barrier layers.

8. The method of claim 3 wherein said nitrogen-containing layers comprise a plurality of barrier layers.

9. The method of claim 7 further comprising the step of providing an arsenic beam equivalent pressure greater than about 1.1e-5 torr during growth of said nitrogen-containing layers.

10. The method of claim 8 further comprising the step of providing an arsenic beam equivalent pressure greater than about 1.64e-5 torr during growth of nitrogen-containing layers.

11. The method of claim 7 where an arsenic flux is created during growth of nitrogen-containing layers and comprises predominantly As₄.

12. The method of claim 1 wherein said nitrogen-free layers comprise said plurality of barrier layers.

13. The method of claim 3 wherein said at least one quantum well includes GaAs, N and at least one of In, Sb and P.

14. The method of claim 12 wherein said barrier layer includes GaAs and at least one of In, Sb, and P.

15. The method of claim 14 wherein said at least one quantum well includes GaAs and at least one of In, Sb and P.

16. The method of claim 15 wherein said at least one quantum well includes N.

39. The method of claim 1 wherein said nitrogen-free layers comprise said at least one quantum well.

17. A method for processing nitrogen-containing active regions associated with a semiconductor laser, said method comprising the steps of:

providing a GaAs substrate;

developing a first confining region including mirror layers above said substrate;

developing an active region including nitrogen containing layers interspersed nitrogen-free layers above said first confining region, wherein said nitrogen containing layers and said nitrogen-free layers are associated with at least one quantum well or at least one barrier layer, said developing an active region further comprising growing at least one nitrogen-free layer by alternately depositing single atomic layers of group III constituents and group V constituents without nitrogen being present, and growing at least one nitrogen containing layer on said at least one nitrogen-free layer; and

developing a second confining region including mirror layers above said active region;

wherein said step of alternately depositing single atomic layers of group III and group V constituents renders a nitrogen-free layer that is substantially flat and useful as a basis for growing at least one nitrogen containing layer.

18. The method of claim 17 wherein said group III and group V constituents comprise Ga and As.

19. The method of claim 17 wherein said at least one nitrogen containing layer is a quantum well.

20. The method of claim 17 wherein said at least one nitrogen containing layer is a barrier layer.

21. The method of claim 17 wherein said at least one nitrogen-free layer is a quantum well.

22. The method of claim 17 wherein said at least one nitrogen-free layer is a barrier layer.

23. The method of claim 19 wherein said quantum well comprises GaAs and at least one of In, Sb and P.

24. The method of claim 20 wherein said barrier layer comprises GaAs and at least one of In, Sb and P.

25. The method of claim 22 wherein said barrier layer comprises GaAs and at least one of In, Sb and P.

26. The method of claim 21 wherein said quantum well comprises GaAs and at least one of In, Sb and P.

27. The method of claim 17 wherein said step of alternately depositing single layers of group III and group V constituents is repeated until at least one of a pre-selected time, temperature or number of alternating layers is achieved.

28. The method of claim 17 wherein said step of alternately depositing single layers of group III and group V constituents is conducted by alternately opening and closing Ga and As shutters associated with a fabrication system used in said method so that said Ga and As shutters are not both open at the same time.

29. The method of claim 17 wherein said step of developing an active region further comprising growing at least one nitrogen-free layer by alternately depositing single atomic layers of group III constituents and group V constituents without nitrogen being present comprises the step of blocking any nitrogen source associated with a fabrication system used for said method.

30. The method of claim 29 wherein said blocking any nitrogen source associated with said fabrication system is conducted by deploying a gate valve located along a nitrogen source line leading into said system.

31. The method of claim 17 wherein said step of alternately depositing single layers of group III and group V constituents is conducted by alternately opening and closing Ga and As shutters associated with a fabrication system used in said method so that said Ga and As shutters are not both open at the same time.

32. The method of claim 17 wherein said step of developing an active region further comprising growing at least one nitrogen-free layer by alternately depositing single atomic layers of group III constituents and group V constituents without nitrogen being present comprises the step of blocking any nitrogen source associated with a fabrication system used for said method.

33. The method of claim 32 wherein said blocking any nitrogen source associated with said fabrication system is conducted by deploying a gate valve located along a nitrogen source line leading into said system.

34. A system for developing an active region containing nitrogen, comprising:

a semiconductor wafer processing chamber;

more than one material source lines coupled to said semiconductor wafer processing chamber, wherein said more than one material source lines carry semiconductor processing material into said semiconductor wafer processing chamber, wherein said semiconductor material includes group III and group V constituents;

at least one shutter associated with each of said more than one material source lines and located inside said semiconductor wafer processing chamber;

a nitrogen source line coupled to said semiconductor wafer processing chamber, said nitrogen source line for providing nitrogen into said semiconductor wafer processing chamber; and

a gate valve located on said nitrogen source line, said gate valve for blocking nitrogen from entering said semiconductor wafer processing chamber when deployed to a closed position;

wherein at least one nitrogen-free layer can be grown within said semiconductor wafer processing chamber by operating said at least one shutter associated with each of said more than one material source lines to alternately deposit single atomic layers of said group III and group V constituents while said gate valve is deployed.

35. The system of claim 34, wherein said material source lines provide Ga, As, In, Sb, P and Al.

36. The system of claim 34 comprising a molecular beam epitaxy processing system.

37. The system of claim 34 comprising a metal-organic chemical vapor disposition processing system.

38. The system of claim 34 comprising a metal-organic vapor phase epitaxy processing system.

40. A method for developing an active region for a semiconductor laser containing nitrogen, said method comprising the steps of:

growing at least one nitrogen-free layer, wherein said nitrogen-free layer remains substantially along its surface in the absence of nitrogen; and

growing at least one nitrogen containing layer on or near said nitrogen-free layer;

wherein said active region contains layers of nitrogen containing layers interspersed with nitrogen-free layers, said nitrogen containing layers and said nitrogen-free layers being associated with at least one quantum well or at least one barrier layer and wherein said step of growing at least one nitrogen-free layer renders at least one semiconductor layer that is substantially flat and useful as a basis for growing at least one nitrogen containing semiconductor layer.