Surface-emission laser diode and fabrication process thereof

• US 8,199,788 B2
• Filed: 01/21/2010
• Issued: 06/12/2012
• Est. Priority Date: 06/11/2004
• Status: Active Grant

• Current Assignee: Ricoh Company Limited
• Original Assignee: Ricoh Company Limited
• Inventors: Sato, Shunichi, Itoh, Akihiro, Jikutani, Naoto
• Primary Examiner(s): Park, Kinam
• Application Number:
  US12/691,476
• Publication Number:
  US 20100118907A1
• Time in Patent Office: 873 Days
• Field of Search: 372/50.124, 372/45.01, 372/45.011, 372/50.11
• US Class Current: 372/50.124
• CPC Class Codes: H01S 5/02251 using optical fibres
• CPC Class Codes: H01S 5/04256 characterised by the configuration
• CPC Class Codes: H01S 5/18311 using selective oxidation
• CPC Class Codes: H01S 5/18347 Mesa comprising active layer
• CPC Class Codes: H01S 5/18383 with periodic active regions at nodes or maxima of light intensity
• CPC Class Codes: H01S 5/2205 comprising special burying or current confinement layers
• CPC Class Codes: H01S 5/343 in AIIIBV compounds, e.g. AlGaAs-laser , InP-based laser
• CPC Class Codes: H01S 5/423 having a vertical cavity

Abstract

A surface-emission laser diode comprises a cavity region over a semiconductor substrate and includes an active layer containing at least one quantum well active layer producing a laser light and a barrier layer, a spacer layer is provided in the vicinity of the active layer and formed of at least one material, an upper and lower reflectors are provided at a top part and a bottom part of the cavity region, the cavity region and the upper and lower reflectors form a mesa structure over the semiconductor substrate, the upper and lower reflectors being formed of a semiconductor distributed Bragg reflector having a periodic change of refractive index and reflecting incident light by interference of optical waves, at least a part of the semiconductor distributed Bragg reflector is formed of a layer of small refractive index of Al_xGa_1-xAs (0<x≦1) and a layer of large refractive index of Al_yGa_1-yAs (0≦y<x≦1), the lower reflector is formed of a first lower reflector having a low-refractive index layer of AlAs and a second lower reflector formed on the first lower reflector, the second lower reflector has a low-refractive index layer of AlGaAs, any one layer constituting the cavity region contains In.

Claims

1. A surface-emission laser diode comprising:

a semiconductor substrate;

a cavity region formed over said semiconductor substrate, said cavity region comprising;

an active layer structural part including at least one quantum well active layer producing a laser light and a barrier layer; and

a spacer layer provided in a vicinity of said active layer structural part, said spacer layer comprising at least one material;

an upper reflector and a lower reflector provided over said semiconductor substrate respectively at a top part and a bottom part of said cavity region,

said upper reflector and said lower reflector constituting a semiconductor distributed Bragg reflector having a periodic change of refractive index and reflecting an incident light by interference of optical waves,

at least a part of said semiconductor distributed Bragg reflector being formed of a layer of small refractive index of Al_xGa_1-xAs (0<

x≦

1) and a layer of large refractive index of Al_yGa_1-yAs (0≦

y<

x≦

1),

said lower reflector being formed of a first lower reflector having a low-refractive index layer of AlAs and a second lower reflector formed on said first lower reflector, said second lower reflector having a low-refractive index layer of AlGaAs, wherein

a part of said spacer layer comprises (Al_aGa_1-a)_bIn_1-bP (0<

a≦

1, 0≦

b≦

1),

said quantum well active layer comprises Ga_cIn_1-cP_dAs_1-d (0≦

c≦

1, 0≦

d≦

1), and

said barrier layer comprises Ga_eIn_1-eP_fAs_1-f (0≦

e≦

1, 0≦

f≦

1).

2. The surface-emission laser diode as claimed in claim 1, wherein at least a lower spacer layer and an upper spacer layer contains In.

3. The surface-emission laser diode as claimed in claim 1, wherein in said second lower reflector, said low refractive index layer and said high refractive index layer are repeated by 10 pairs or less.

4. The surface-emission laser diode as claimed in claim 1, wherein said quantum well active layer has a compressive strain.

5. The surface-emission laser diode as claimed in claim 1, wherein said barrier layer has a tensile strain.

6. The surface-emission laser diode as claimed in claim 1, wherein said semiconductor substrate comprises a (100) GaAs substrate having a surface orientation inclined in a direction of a (111)A surface with an angle in a range of 5°

to 20°

.

7. The surface-emission laser diode as claimed in claim 1, wherein said surface-emission laser diode has an oscillation wavelength of about 680 nm or longer.

8. The surface-emission laser diode as claimed in claim 1, wherein said semiconductor substrate comprises a (100) GaAs substrate having a surface orientation inclined in a direction of a (111)A surface by an angle in a range of 5°

to 20°

.

9. The surface-emission laser diode as claimed in claim 1, wherein said surface-emission laser diode has an oscillation wavelength of about 680 nm or longer.

10. An image forming apparatus comprising:

a photosensitive body;

an optical system that focuses one or more light beams upon the photosensitive body to form an optical image on the photosensitive body; and

one or more surface-emission laser diodes that generates said one or more light beams, respectively, each surface-emission laser diode of the one or more surface-emission laser diodes comprising;

a semiconductor substrate;

a cavity region formed over said semiconductor substrate, said cavity region comprising;

an active layer structural part including at least one quantum well active layer producing a laser light and a barrier layer; and

a spacer layer provided in a vicinity of said active layer structural part, said spacer layer comprising at least one material; and

an upper reflector and a lower reflector provided over said semiconductor substrate respectively at a top part and a bottom part of said cavity region, wherein

said upper reflector and said lower reflector constitute a semiconductor distributed Bragg reflector having a periodic change of refractive index and reflecting an incident light by interference of optical waves,

at least a part of said semiconductor distributed Bragg reflector is formed of a layer of small refractive index of Al_xGa_1-xAs (0<

x≦

1) and a layer of large refractive index of Al_yGa_1-yAs (0≦

y<

x≦

1), and

said lower reflector includes a first lower reflector having a low-refractive index layer of AlAs and a second lower reflector formed on said first lower reflector, said second lower reflector having a low-refractive index layer of AlGaAs, and wherein

a part of said spacer layer comprises (Al_aGa_1-a)_bIn_1-bP (0<

a≦

1, 0≦

b≦

1),

said quantum well active layer comprises Ga_cIn_1-cP_dAs_1-d (0≦

c≦

1, 0≦

d≦

1), and

said barrier layer comprises Ga_eIn_1-eP_fAs_1-f (0≦

e≦

1, 0≦

f≦

1).

11. An optical transmission apparatus comprising:

one or more optical transmission media that carry respective light beams; and

one or more surface-emission laser diodes that generates said light beams, respectively, each surface-emission laser diode of the one or more surface-emission laser diodes comprising;

a semiconductor substrate;

a cavity region formed over said semiconductor substrate, said cavity region comprising;

an active layer structural part including at least one quantum well active layer producing a laser light and a barrier layer; and

a spacer layer provided in a vicinity of said active layer structural part, said spacer layer comprising at least one material; and

an upper reflector and a lower reflector provided over said semiconductor substrate respectively at a top part and a bottom part of said cavity region, wherein

said upper reflector and said lower reflector constitute a semiconductor distributed Bragg reflector having a periodic change of refractive index and reflecting an incident light by interference of optical waves,

at least a part of said semiconductor distributed Bragg reflector is formed of a layer of small refractive index of Al_xGa_1-xAs (0<

x≦

1) and a layer of large refractive index of Al_yGa_1-yAs (0≦

y<

x≦

1), and

said lower reflector includes a first lower reflector having a low-refractive index layer of AlAs and a second lower reflector formed on said first lower reflector, said second lower reflector having a low-refractive index layer of AlGaAs, and wherein

a part of said spacer layer comprises (Al_aGa_1-a)_bIn_1-bP (0<

a≦

1, 0≦

b≦

1),

said quantum well active layer comprises Ga_cIn_1-cP_dAs_1-d (0≦

c≦

1, 0≦

d≦

1), and

said barrier layer comprises Ga_eIn_1-eP_fAs_1-f (0≦

e≦

1, 0≦

f≦

1).