SEMICONDUCTOR LASER DIODE AND ITS FABRICATION PROCESS

• US 20080181276A1
• Filed: 01/31/2008
• Published: 07/31/2008
• Est. Priority Date: 01/31/2007
• Status: Active Grant

• Current Assignee: USHIO Opto Semiconductors, Inc. (Ushio Incorporated)
• Original Assignee: Opnext Japan, Inc. (Oclaro (Canada), Inc.)
• Inventors: Hara, Hideki, Nakamura, Atsushi, Kawanaka, Satoshi, Yamamoto, Masakatsu, Hagimoto, Masato
• Granted Patent: US 7,746,910 B2
• Time in Patent Office: Days
• US Class Current: 372/45.013
• CPC Class Codes: B82Y 20/00 Nanooptics, e.g. quantum optics or photonic crystals
• CPC Class Codes: H01S 2301/18 Semiconductor lasers with special structural design for influencing the near- or far-field
• CPC Class Codes: H01S 5/0202 Cleaving
• CPC Class Codes: H01S 5/028 Coatings ; Treatment of the laser facets, e.g. etching, passivation layers or reflecting layers
• CPC Class Codes: H01S 5/0282 Passivation layers or treatments
• CPC Class Codes: H01S 5/0287 Facet reflectivity
• CPC Class Codes: H01S 5/1017 Waveguide having a void for insertion of materials to change optical properties
• CPC Class Codes: H01S 5/22 having a ridge or stripe structure
• CPC Class Codes: H01S 5/34326 with a well layer based on InGa(Al)P, e.g. red laser

Abstract

A semiconductor laser diode device with small driving current and no distortion in the projected image. The semiconductor laser diode includes an n-GaAs substrate and, an n-cladding layer on the n-GaAs substrate, an active layer, a p-clad layer, a multilayer formed from sequentially laminated p-contact layers, and a ridge formed by selectively etching from the upper surface of the p-contact active layer to a specified depth on the p-contact layer, and an insulating film deposited on the upper surface side of the n-GaAs substrate, and formed from the side surface of the ridge to the edge periphery of the n-GaAs substrate, and a p-electrode formed on the insulating layer deposited on the ridge of the P-contact layer, and an n-type electrode formed on the lower surface of the n-GaAs substrate; and the n-GaAs substrate structure possesses a side edge serving as an absorption layer to absorb light emitted at the active layer wavelength; and a groove is fabricated at the side edge forming the front facet (forward emission side), to a depth from the p-cladding layer exceeding the active layer, from a p-cladding layer section a specified distance away from the side of the ridge along the edge, to the side of the active layer; and the groove is covered by the insulating layer.

Claims

1. A semiconductor laser diode device comprising:

a square semiconductor substrate made from a first conductive type semiconductor, and including a first surface and a second surface as the side opposite the first surface;

a multiple epitaxial layer including sequentially forming at least a first conductive cladding layer, an active layer, a second conductive cladding layer and second conductive contact layer on the first surface of the semiconductor substrate;

a ridge structure formed by selectively etching from the upper surface of the second conductive contact layer to a specified depth on the second conductive cladding layer, and extending in a stripe shape extending between one pair of facets opposite each other on the semiconductor substrate along the edge;

an insulating layer formed over the first surface side of the semiconductor substrate on a section from the side surface of the ridge to the periphery of the semiconductor substrate;

a second electrode formed over the insulating layer over the second conductive contact layer of the ridge, and

a first electrode formed on the second surface of the semiconductor substrate,

wherein the semiconductor substrate contains bandpass energy serving as an absorption layer for light on the emission wavelength of the active layer, or the refractive index value for all semiconductor layers between the active layer and the semiconductor substrate is larger than the semiconductor substrate refractive index value,

wherein grooves are formed on both sides at one end of the ridge, along the end edge and from the second cladding layer separated a specified distance from the side edge of the ridge to the side of the active layer, and at a depth from the second conductive cladding layer exceeding the active layer, and

wherein the groove is covered by an insulating layer.

2. The semiconductor laser diode device according to claim 1, wherein a facet coating layer is formed on one facet of the ridge, and a facet coating layer with the same or higher reflectivity is formed on the other side of the ridge.

3. The semiconductor laser diode device according to claim 1, wherein the distance between the side of the groove and the one end of the ridge is 3 to 50 micrometers.

4. The semiconductor laser diode device according to claim 1, wherein the groove width is 1 to 50 micrometers.

5. The semiconductor laser diode device according to claim 1, wherein the distance from the ridge side to the side of the groove is 1 to 15 micrometers.

6. The semiconductor laser diode device according to claim 1, wherein the upper edge of the insulating layer is at a position deeper than the lower edge of the active layer in the deepest section of the groove.

7. The semiconductor laser diode device according to claim 1, wherein the inner circumferential section where the active layer is exposed on the inner circumferential surface of the groove becomes an oblique surface with the groove width becoming gradually narrower as the groove becomes deeper.

8. The semiconductor laser diode device according to claim 1, wherein the semiconductor substrate is a structure containing bandgap energy that functions as a light absorbing layer to absorb light on the emission wavelength of the active layer, and the semiconductor substrate is a GaAs substrate, and the first conductive cladding layer is made from AlGaInP, and the active layer is a single layer structure made from (Al)GaInP or is a multiple quantum well structure made where the quantum well is made from GaInP and the quantum barrier made from AlGaInP, and the second conductive cladding layer is made from AlGaInP, and the second conductive contact layer is made from GaAs with a lasing (light emission) wavelength from 600 to 690 nanometers.

9. The semiconductor laser diode device according to claim 1, wherein the semiconductor substrate is a structure containing bandgap energy that functions as a light absorbing layer to absorb light on the emission wavelength of the active layer, and semiconductor substrate is a GaAs substrate, and the first conductive cladding layer is made from AlGaInP, and the active layer is a single layer structure made from InGaAsP or is a multiple quantum well structure where the quantum well is made from InGaAsP and a quantum barrier is made from AlGaInP, and the second conductive cladding layer is made from AlGaInP, and the second conductive contact layer is made from GaAs with a lasing (light emission) wavelength from 600 to 690 nanometers.

10. The semiconductor laser diode device according to claim 1, wherein refractive index values for all semiconductor layers between the active layer and the semiconductor substrate are larger than the refractive index value of the semiconductor substrate, and the semiconductor substrate is a Ga(As)P substrate, and the first conductive cladding layer is made from AlGaInP, and the active layer is a single layer structure made from (Al)GaInP or is a multiple quantum well structure where the quantum well is made from GaInP and the quantum barrier made from AlGaInP, and the second conductive cladding layer is made from AlGaInP, and the second conductive contact layer is made from GaAs, and the lasing wavelength is 560 to 640 nanometers.

11. A semiconductor laser diode device comprising:

a square semiconductor substrate made from a first conductive type semiconductor, containing a first surface and a second surface forming the side opposite the first surface;

a multiple epitaxial layer of sequentially formed semiconductor layers including at least a first conductive cladding layer, an active layer and a second conductive cladding layer on at a first surface of the semiconductor substrate;

a ridge structure formed in a stripe shape extending between one pair of facets opposite each other on the semiconductor substrate by selectively etching from the upper surface of the second conductive cladding layer to a specified depth on the second cladding layer;

a first conductive current blocking layer pair formed from a first conductive type semiconductor layer enclosing the ridge, and formed on the second conductive cladding layer remaining on both sides of the ridge;

a second conductive contact layer made from the second conductive type semiconductor layer formed on the current blocking layer and the ridge;

a second electrode formed over the second conductive contact layer, and

a first electrode formed over the second surface of the semiconductor substrate,

wherein the first conductive current blocking layer is a structure containing bandgap energy transparent to light on the emission wavelength of the active layer,

wherein grooves are formed on one end on both ends of the ridge, along the end edge and from the second conductive contact layer separated a specified distance from the side edge of the ridge to the side of the active layer, and at a depth from the second conductive contact layer exceeding the active layer,

wherein the groove is covered by an insulating layer, and

wherein the second electrode is formed over the insulating layer in the groove section.

12. The semiconductor laser diode device according to claim 11, wherein the semiconductor substrate is a GaAs substrate, the first conductive cladding layer is made from AlGaInP, the active layer is a single layer structure made from (Al)GaInP or is a multiple quantum well structure where the quantum well is GaInP and the quantum barrier is made from AlGaInP, the second conductive cladding layer is made from AlGaInP, and the first conductive current blocking layer is made from Al (Ga) InP, and the second conductive contact layer is made from GaAs.

13. A fabrication process for semiconductor laser diode devices comprising:

(a) a process for preparing a first conductive type semiconductor substrate containing a first surface, and a second surface opposite the first surface, and multiple square laser diode forming regions arrayed lengthwise and widthwise on the first surface;

(b) a process for forming in sequence by metal-organic chemical vapor deposition method;

a first conductive cladding layer from a first conductive type semiconductor layer on the first surface of the semiconductor substrate, an active layer from the semiconductor layer, a second conductive cladding layer from the second conductive type semiconductor layer and a second conductive contact layer from the second conductive type semiconductor layer;

(c) a process for forming a ridge structure by selectively removing each semiconductor layer on the first surface of the semiconductor substrate, to one-dimensionally and consecutively form a stripe ridge along the center of the laser diode forming region and in a thickness from the upper surface of the exposed side of the second conductive contact layer to the center layer of the second conductive cladding layer;

(d) a process for forming a groove in each square shaped laser diode forming region, on one of a pair of first sides along a direction intersecting the ridge structure, and from a position isolated a specified distance away from the ridge structure on the inner side of one side to a pair of second sides intersecting the pair of first sides, and at a depth from the second conductive cladding layer exceeding the active layer;

(e) a process for forming an insulating layer on each laser diode forming region, by exposing the second conductive contact layer for exposure along the center of the ridge structure, and also forming the insulating layer to cover the first side of the remaining semiconductor substrate;

(f) a process for forming a second electrode over the second conductive contact layer and also to selectively cover the insulating layer on each laser diode forming region;

(g) a process to remove a specified thickness of the second surface on the semiconductor substrate;

(h) a process for forming a first electrode on the second surface on the semiconductor substrate of each laser diode forming region;

(i) a process for forming short strips (bars) by cleaving the semiconductor substrate at each first side on the laser diode forming region;

(j) a process for forming a coating film on the cleaved facet in the vicinity of the groove of the short strip and, forming a coating film whose reflectivity is larger than or equal to the coating film on the cleaved surface far from the groove of the short strip; and

(k) a process for separating the short strips (bars) respectively at the second side of the laser diode forming region.

14. The fabrication process for semiconductor laser diode devices according to claim 13, wherein in the process (d), the groove is formed on the inner side, at a position 3 to 50 micrometers away from the inner side of one of the first sides.

15. The fabrication process for semiconductor laser diode devices according to claim 13, wherein in the process (d), the distance between the side of the groove and the side edge of the ridge structure is 1 to 15 micrometers.

16. The fabrication process for semiconductor laser diode devices according to claim 13, wherein in the forming of the groove in the process (d), and the forming of the insulating film in the process (e), the upper edge of the deepest section of the insulator layer formed in the bottom of the groove, is deeper than the lower edge of the active layer.

17. The fabrication process for semiconductor laser diode devices according to claim 13, wherein in the process (d), the exposed inner circumferential surface of the active layer on the inner circumferential surface of the groove, forms an oblique surface with the groove width gradually narrowing as the groove becomes deeper.

18. The fabrication process for semiconductor laser diode devices according to claim 13,

wherein the semiconductor substrate contains bandgap energy that functions as a light absorbing layer to absorb light on an emission wavelength emitted from the active layer, and a GaAs substrate is prepared in the process (a) as a semiconductor substrate to attain a lasing wavelength from 600 to 690 nanometers, and

wherein in the process (b), a first conductive cladding layer is formed from AlGaInP, and the active layer is a single layer structure made from (Al)GaInP or is a multiple quantum well structure where the quantum well is GaInP and the quantum barrier is made from AlGaInP, the second conductive cladding layer is made from AlGaInP, and the second conductive contact layer is made from GaAs.

19. The fabrication process for semiconductor laser diode devices according to claim 13,

wherein the semiconductor substrate contains bandgap energy that functions as a light absorbing layer to absorb light on an emission wavelength emitted from the active layer, and a GaAs substrate is prepared in the process (a) as a semiconductor substrate to attain a lasing wavelength from 600 to 690 nanometers, and

wherein in the process (b), a first conductive cladding layer is formed from AlGaiInP, and the active layer is a single layer structure made from InGaAsP or is a multiple quantum well structure made from AlGaInP where the quantum well is InGaAsP and the quantum barrier is made from AlGaInP, the second conductive cladding layer is made from AlGaInP, and the second conductive contact layer is made from GaAs.

20. The fabrication process for semiconductor laser diode devices according to claim 13,

wherein the refractive index value for all semiconductor layers between the active layer and the semiconductor substrate is larger than the semiconductor substrate refractive index value, and a Ga(As)P substrate is prepared in the process (a) as a semiconductor substrate to attain a lasing wavelength from 560 to 640 nanometers, and

wherein in the process (b), a first conductive cladding layer is formed from AlGaInP, and the active layer is a single layer structure made from (Al)GaInP or is a multiple quantum well structure where the quantum well is GaInP and the quantum barrier is made from AlGaInP, the second conductive cladding layer is made from AlGaInP, and the second conductive contact layer is made from GaAs.