JP2007103783A - Semiconductor laser - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor laser capable of restraining variations such as the gradual increase of light intensity in a pulse light output. <P>SOLUTION: A p-type (Al<SB>0.70</SB>Ga<SB>0.30</SB>)InP second cladding layer 5, an undoped GaInP etching stop layer 6, a third p-type (Al<SB>0.70</SB>Ga<SB>0.30</SB>)InP cladding layer 7, a p-type GaInP intermediate layer 8, and a p-type GaAs contact layer 9 are formed successively on an SCH (separated and entrapped hetero structure)-MQW (multiple quantum well structure) comprising undoped GaInP/AlGaInP. The third p-type (Al<SB>0.70</SB>Ga<SB>0.30</SB>)InP cladding layer 7, a p-type GaInP intermediate layer 8, and a p-type GaAs contact layer 9 compose a ridge 13 that becomes one part of a current passage. The angle of the horizontal radiation of laser beams emitted by an active layer 4 is 8.7°, and a differential resistance value is 6.0 Ω in an operating current. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a semiconductor laser used for a light source device for a laser beam printer, for example.

  In recent years, red semiconductor lasers have been used as light sources for high-speed laser printers, in addition to their use as write and read light sources for DVD (Digital Universal Disc) disks.

  When a semiconductor laser is used in a laser printer, the semiconductor laser is intermittently driven by a pulse current. At this time, if the light intensity varies in the pulsed light output, the printing blurs and the printing color unevenness occurs. The problem arises.

  As shown in FIG. 4A, the fluctuation of the light intensity is evaluated by a droop defined by (P1-P2) / P1 from the light intensity P1 at the time of the pulse rise and the light output P2 at the end of the pulse.

  The fluctuation in light intensity as shown in FIG. 4A is caused by heat generation when the semiconductor laser is energized. More specifically, when the semiconductor laser is energized, heat is generated due to Joule heat, and the temperature of the active layer rises due to the effect of this heat generation, resulting in a decrease in light intensity.

  As a method of reducing the droop due to the heat generation factor as described above, a method of suppressing heat generation such as lowering the operating current, lowering the operating voltage, improving heat dissipation of the package, and reducing the slope efficiency of the laser characteristics, There is a method for making it difficult for the light intensity to decrease even when the threshold current Ith increases. Measures such as reduction of the threshold current Ith and higher reflectance of the front surface reflectance are taken for the semiconductor laser using these methods.

  However, the semiconductor laser has a characteristic that the light intensity gradually increases as shown in FIG. 4B, in addition to the fluctuation of the pulsed light output due to the heat generation factor. When a semiconductor laser having this characteristic is used in a laser printer, sufficient light intensity cannot be obtained when a short pulse is applied, resulting in a problem of printing deterioration.

  In particular, the above problem becomes significant in a high-speed laser printer using nanosecond order pulse drive.

It is known that the fluctuation in which the light intensity gradually increases as described above appears remarkably in a multimode laser such as a gain guide laser.
JP 2000-299526 A JP 2002-374040 A JP-A-1-205588 JP-A-5-37085

  Therefore, an object of the present invention is to provide a semiconductor laser capable of suppressing fluctuations in which the light intensity gradually increases in pulsed light output.

  The inventors of the present invention have studied the pulsed light output of a red semiconductor laser, which is an example of a semiconductor laser, to suppress fluctuations in light intensity that gradually increase after the rise of the pulse. And both have a relationship with increasing fluctuations in light output, and by setting both the resistance value and the ridge width within a limited range, it has been found that fluctuations in light intensity can be suppressed.

  In order to express the change rate of the pulsed light output in the present invention, as shown in FIG. 5, the light emission rate is defined as the ratio of the light intensity of the pulsed light output by the pulse current when the light intensity in continuous driving is used as a reference. To do. If there is a slow increase in light intensity after the rise of the pulse, sufficient pulse light intensity cannot be obtained during short pulse drive, the light emission rate is small, and the light intensity expected by pulse drive cannot be obtained, resulting in poor printing. Problems arise.

  FIG. 6 shows the results of investigating the serial resistance dependence of the light emission rate with various red semiconductor lasers having different structures. FIG. 7 shows the results of examining the horizontal radiation angle dependence of various red semiconductor lasers having different structures.

  As can be seen from FIGS. 6 and 7, the light emission rate decreases when the horizontal radiation angle is small, and similarly decreases when the series resistance is large. The horizontal radiation angle is determined by the ridge width of the semiconductor laser. When the ridge width is wide, the horizontal radiation angle becomes narrow, while the series resistance becomes small when the ridge width becomes wide. For this reason, the horizontal radiation angle and the series resistance are each independently dependent on the light emission rate. In order to eliminate the problem of printing quality in the laser printer, it is necessary to set the light emission rate within the range of 90% to 110%. This can be achieved by setting the series resistance to 6.5 Ω or less and the horizontal radiation angle to 8.5 degrees or more.

  The increase in light intensity after the rise of the pulse is considered to be determined by the time required for lateral diffusion until the carrier distribution in the active layer stabilizes in the steady oscillation state. Changes in the carrier distribution in the active layer can be suppressed by not spreading the waveguide of the laser light into a region where the amount of current injection is reduced, that is, a region where there are few carriers in the active layer. The wider the horizontal emission angle, the laser emission width becomes smaller than the ridge width, and the smaller the series resistance, the more uniformly the injected current flows into the ridge, particularly to the active layer side region on the side of the ridge. As a result, the larger the horizontal radiation angle and the smaller the series resistance, the smaller the change in carrier distribution in the active layer, and the less the change in light intensity after the pulse rises.

  On the other hand, if the ridge width is too narrow in order to narrow the horizontal radiation angle, the current path is also narrowed and the series resistance becomes high, causing problems such as an increase in operating current in addition to a decrease in light emission rate. On the other hand, if the series resistance is 4Ω or less and the horizontal radiation angle is 10 ° or more, the luminous efficiency exceeds 110% due to the influence of relaxation oscillation in the pulse response.

In view of the above, in order to solve the above problems, the semiconductor laser of the present invention is
An active layer,
A p-type cladding layer formed directly or indirectly on the active layer;
A p-type cap layer formed on the p-type cladding layer via a semiconductor layer,
A current path from the p-type cap layer to the p-type cladding layer has a striped ridge formed of at least three semiconductor layers having different band gaps;
The horizontal radiation angle is 8.5 degrees or more, and the differential resistance value at the operating current is 6.5 Ω or less,
It emits red laser light and is characterized by being an AlGaInP system.

  According to the semiconductor laser having the above configuration, the horizontal radiation angle (full width at half maximum of the far-field image) is 8.5 degrees or more and the differential resistance value in the operating current is 6.5 Ω or less. The ratio of the pulsed light output intensity due to the pulse current (light emission rate in FIG. 5) in the range of 90% to 110% in the order of nanoseconds when the light output intensity in the continuous drive is used as a reference. The fluctuation that gradually increases can be suppressed.

  In addition, since the above-mentioned semiconductor laser has the above-mentioned emission rate in the range of 90% to 110% in the order of nanoseconds, for example, when used in a laser beam printer, the emission pulse intensity becomes a desired intensity, and color unevenness and the like. Occurrence of printing deterioration can be prevented.

In the semiconductor laser of one embodiment,
The radiation angle is 9.0 degrees or more, and the differential resistance value is 5.0Ω or more.

In the semiconductor laser of one embodiment,
The width of the end on the active layer side of the p-type cladding layer is 3.5 μm or more and 4.5 μm or less.

In the semiconductor laser of one embodiment,
The ridge includes the p-type cladding layer;
The p-type cladding layer has a thickness of 0.6 μm or more and 0.8 μm or less.

In the semiconductor laser of one embodiment,
The radiation angle is 9.5 degrees or less, and the differential resistance value is 6.0 Ω or less.

In the semiconductor laser of one embodiment,
The radiation angle is 9.0 degrees or more and 9.5 degrees or less, and the differential resistance value is 5.0Ω or more and 6.0Ω or less.

  According to the semiconductor laser of the above embodiment, the radiation angle is 9.0 degrees or more and 9.5 degrees or less, and the differential resistance value is 5.0Ω or more and 6.0Ω or less. The ratio of the pulsed light output intensity based on the pulsed current based on the light output intensity (the light emission rate in FIG. 5) can be in the range of 95% to 105% in nanosecond order.

In the semiconductor laser of one embodiment,
The laser beam is a single mode laser beam from an oscillation threshold value to a normal light output of 0.5 mW to 10 mW.

In the semiconductor laser of one embodiment,
The current path is composed of p-type GaAs, p-type GaInP, and p-type AlGaInP.

In the semiconductor laser of one embodiment,
The p-type impurity concentration of the p-type GaInP is 5.0 × 10 ¹⁸ cm ⁻³ or more and 1.5 × 10 ¹⁹ cm ⁻³ or less,
The p-type AlGaInP has a p-type impurity concentration of 2.0 × 10 ¹⁸ cm ⁻³ or more and 2.5 × 10 ¹⁸ cm ⁻³ or less.

In the semiconductor laser of one embodiment,
The heat treatment is performed at 700 ° C. to 800 ° C. for 1 minute to 30 minutes.

In the semiconductor laser of one embodiment,
A p-type cladding layer formed between the active layer and the p-type cladding layer and having a carrier concentration lower than that of the p-type cladding layer is provided.

In the semiconductor laser of one embodiment,
The p-type cladding layer having the low carrier concentration has a p-type impurity concentration of 1.5 × 10 ¹⁸ cm ⁻³ or more and 2.0 × 10 ¹⁸ cm ⁻³ or less.

In the semiconductor laser of one embodiment,
A current blocking layer is formed on both sides of the ridge and has a depletion layer width of 0.30 μm or more during laser operation.

In the semiconductor laser of one embodiment,
The thickness of the region having a carrier concentration of 2 × 10 ¹⁷ cm ⁻³ or less in the current blocking layer is 0.30 μm or more.

  According to the semiconductor laser of the present invention, since the horizontal radiation angle is 8.5 degrees or more and the differential resistance value at the operating current is 6.5 Ω or less, the light output intensity in continuous driving is used as a reference. The ratio of the pulsed light output intensity due to the pulse current is in the range of 90% to 110% in the order of nanoseconds, and fluctuations in which the light intensity gradually increases in the pulsed light output can be suppressed.

  In addition, since the above-mentioned semiconductor laser has the above-mentioned emission rate in the range of 90% to 110% in the order of nanoseconds, for example, when used in a laser beam printer, the emission pulse intensity becomes a desired intensity, and color unevenness and the like. Occurrence of printing deterioration can be prevented.

  Hereinafter, the semiconductor laser of the present invention will be described in detail with reference to the illustrated embodiments.

(First embodiment)
FIG. 1 is a schematic sectional view of a red semiconductor laser for a laser printer according to a first embodiment of the present invention.

In the red semiconductor laser, an n-type GaInP buffer layer 2 (Si: 1 × 10 ¹⁸ cm ⁻³ doped, thickness: 0.5 μm) and an n-type (Al _0.70 Ga _{0. 30} ) SCH (separate confinement heterostructure) -MQW (multiple quantum well structure) activity comprising InP first cladding layer 3 (Si: 1 × 10 ¹⁸ cm ⁻³ doped, thickness: 1.0 μm) and undoped GaInP / AlGaInP Layer 4, p-type (Al _0.70 Ga _0.30 ) InP second cladding layer 5 (Be: 2.0 × 10 ¹⁸ cm ⁻³ doped, thickness 0.18 μm), undoped GaInP etching stop layer 6 (Thickness 8 nm), p-type (Al _0.70 Ga _0.30 ) InP third cladding layer 7 (Be: 2.0 × 10 ¹⁸ cm ⁻³ doped, thickness 0.8 μm), p-type GaI An nP intermediate layer 8 (Be: 7.0 × 10 ¹⁸ cm ⁻³ doped, thickness 50 nm) and a p-type GaAs contact layer 9 (Be: 5.0 × 10 ¹⁸ cm ⁻³ ) as an example of a p-type cap layer. Dope, thickness of 0.5 μm) is formed sequentially.

The SCH-MQW active layer 4 is an MQW composed of a GaInP quantum well layer (4 layers, thickness 6 nm) and an (Al _0.50 Ga _0.50 ) InP barrier layer (3 layers, thickness 5 nm), (Al _0.50 Ga _0.50 ) InP guide layer (thickness 50 nm).

p-type _{(Al 0.70 Ga} 0.30) InP third clad layer 7, p-type GaInP intermediate layer 8 and the p-type GaAs contact layer 9 constitute a ridge 13, the current path of the ridge 13 is a semiconductor laser Part of

Flat portions on both sides of the ridge 13 are formed by an etching stop layer 6, which is thinner than the p-type (Al _0.70 Ga _0.30 ) InP third cladding layer 7. An n-type GaAs current blocking layer 12 is formed on the flat portion.

  A p-side electrode 10 made of Au / Mo / AuZn is formed on the n-type GaAs current blocking layer 12 and the p-type GaAs contact layer 9. On the other hand, an n-side electrode 11 made of Au / Mo / Au / Ni / AuGe is formed on the back surface of the n-type GaAs substrate 1 (the surface opposite to the surface on the SCH-MQW active layer 4 side).

In the method for manufacturing a red semiconductor laser having the above configuration, first, an n-type GaInP buffer layer, an n-type (Al _0.70 Ga _0.30 ) is formed on an n-type GaAs substrate by using a known MBE (molecular beam epitaxial growth) method. ) InP first cladding layer, SCH-MQW active layer, p-type (Al _0.70 Ga _0.30 ) InP second cladding layer, undoped GaInP etching stop layer, p-type (Al _0.70 Ga _0.30 ) InP A third cladding layer, a p-type GaInP intermediate layer, and a p-type GaAs contact layer are sequentially grown.

Next, a region that becomes the ridge 13 is formed from the p-type (Al _0.70 Ga _0.30 ) InP third cladding layer, the p-type GaInP intermediate layer, and the p-type GaAs contact layer by using known photolithography and etching techniques. The part other than is selectively removed. The width of the ridge 13 is determined by the width of the etching mask used in this photolithography. Here, the width of the etching mask is set so that the width of the ridge 13 on the SCH-MQW active layer 4 side is 4.5 μm.

  Next, an n-type GaAs current blocking layer is grown (regrown) by the MBE method.

  Next, an unnecessary layer grown on the region to be the ridge 13 is selectively removed by etching, and then a p-side electrode and an n-side electrode are formed, thereby completing a wafer including a laser structure.

Next, after a bar having a resonator length of 350 μm is cut out from the wafer, an Al ₂ O ₃ film is coated on the front end face and the rear end face of the bar. This Al ₂ O ₃ film is formed so that the reflectance of the front end face and the rear end face of the bar is 35%.

Finally, when a bar whose front end face and rear end face are coated with the Al ₂ O ₃ film is divided into chips, a plurality of red semiconductor lasers are obtained.

  The red semiconductor laser was attached to the SiC submount at a junction down, and the SiC submount was attached to the 5,6φ stem to complete the laser device.

  The laser device oscillated with a threshold current Ith = 30 mA at room temperature and operated at a maximum rating of 70 ° C. and 7 mW. The oscillation wavelength was 654 nm, and the single mode was operated up to the maximum rating.

  Further, when the differential resistance value and horizontal emission angle of the red semiconductor laser were examined using the above laser apparatus, the differential resistance value was 6.0Ω and the horizontal emission angle was 8.7 degrees.

  When the red semiconductor laser was operated with no bias at the time of pulse-off and with a pulse output of 3 mW, the light emission rate at a pulse width of 40 ns was good at 98%.

(Second Embodiment)
FIG. 2 is a schematic cross-sectional view of a red semiconductor laser for a laser printer according to a second embodiment of the present invention.

In the red semiconductor laser, an n-type GaInP buffer layer 2 (Si: 1 × 10 ¹⁸ cm ⁻³ doped, thickness: 0.5 μm) and an n-type (Al _0.70 Ga _{0. 30} ) InP first cladding layer 3 (Si: 1 × 10 ¹⁸ cm ⁻³ doped, thickness: 1.0 μm), SCH-MQW active layer 4 made of undoped GaInP / AlGaInP, and p-type (Al _0.70 Ga) _0.30 ) InP second cladding layer 5 (Be: 2.0 × 10 ¹⁸ cm ⁻³ doped, thickness 0.18 μm), undoped GaInP etching stop layer 6 (thickness 8 nm), p-type (Al _{0 .70} Ga _0.30 ) InP third cladding layer 7 (Be: 2.0 × 10 ¹⁸ cm ⁻³ doped, thickness 0.8 μm) and p-type GaInP intermediate layer 8 (Be: 7.0 × 10 ¹⁸⁾ cm ^- Doped, the thickness 50 nm), a p-type GaAs contact layer 9 as an example of a p-type cap layer ^{(Be: 5.0 × 10 18 cm} -3 doping, 0.5 [mu] m thickness) and are sequentially formed.

The SCH-MQW active layer 4 is an MQW composed of a GaInP quantum well layer (4 layers, thickness 6 nm) and an (Al _0.50 Ga _0.50 ) InP barrier layer (3 layers, thickness 5 nm), (Al _0.50 Ga _0.50 ) InP guide layer (thickness 50 nm).

The p-type (Al _0.70 Ga _0.30 ) InP third cladding layer 7, the p-type GaInP intermediate layer 8 and the p-type GaAs contact layer 9 constitute a ridge 13, which is a part of the semiconductor laser. It becomes.

Flat portions on both sides of the ridge 13 is formed by the etching stop layer 6 is thinner than the etching stop layer 6 is p-type _{(Al 0.70 Ga} 0.30) InP third clad layer 7. A current blocking layer 124 is formed on the flat portion.

The current blocking layer 124 includes a p-type GaAs layer 121 (Be: 1.0 × 10 ¹⁷ cm ⁻³ doped, thickness 0.15 μm) and an n-type GaAs layer 122 (Si) formed on the p-type GaAs layer 121. : 1.0 × ¹⁰ 17 ^{cm -3} doping, and thickness 0.15 [mu] m), the n-type GaAs layer 122 n-type GaAs layer formed on ^{123 (Si: 1.0 × 10 18} cm -3 doping, And a thickness of 0.50 μm).

  A p-side electrode 10 made of Au / Mo / AuZn is formed on the current blocking layer 124 and the p-type GaAs contact layer 9. On the other hand, an n-side electrode 11 made of Au / Mo / Au / Ni / AuGe is formed on the back surface of the n-type GaAs substrate 1 (the surface opposite to the surface on the SCH-MQW active layer 4 side).

  The width of the ridge 13 is controlled by the etching mask width in photolithography as in the first embodiment. More specifically, the width of the ridge 13 on the SCH-MQW active layer 4 side is 4.5 μm.

The red semiconductor laser having the above configuration is obtained by cutting a bar having a cavity length of 350 μm from a wafer on which a predetermined laser structure is formed, and then chip-dividing the front end face and rear end face of the bar with an Al ₂ O ₃ film. Have gained. Here, the Al ₂ O ₃ film is formed so that the reflectance of the front end face and the rear end face of the bar is 35%.

  The red semiconductor laser was attached to the SiC submount at a junction down, and the SiC submount was attached to the 5,6φ stem to complete the laser device.

  When the differential resistance value and horizontal emission angle of the red semiconductor laser were examined using the above laser device, the differential resistance value was 6.0Ω and the horizontal emission angle was 8.7 degrees.

In the second embodiment, the current blocking layer 124 has a p ⁻ / n type / n ⁺ junction structure, and the depletion layer can be expanded to a thickness of 0.30 μm or more in this region during laser operation. As a result, the parallel capacitance of the laser element is reduced, and the time constant of the pulse response determined by the product of the capacitance and the resistance value of the element can be shortened.

  When the red semiconductor laser of the second embodiment was operated with no pulse-off bias and a pulse output of 3 mW, the light emission rate at a pulse width of 20 ns was good at 98%.

(Third embodiment)
FIG. 3 is a schematic cross-sectional view of a red semiconductor laser for a laser printer according to a third embodiment of the present invention.

In the red semiconductor laser, an n-type GaInP buffer layer 2 (Si: 1 × 10 ¹⁸ cm ⁻³ doped, thickness: 0.5 μm) and an n-type (Al _0.70 Ga _{0. 30} ) InP first cladding layer 3 (Si: 1 × 10 ¹⁸ cm ⁻³ doped, thickness: 1.0 μm), SCH-MQW active layer 4 made of undoped GaInP / AlGaInP, and p-type (Al _0.70 Ga) _0.30 ) InP second cladding layer 5 (Be: 1.5 × 10 ¹⁸ cm ⁻³ doped, thickness 0.18 μm), undoped GaInP etching stop layer 6 (thickness 8 nm), p-type (Al _{0 .70} Ga _0.30 ) InP third cladding layer 7 (Be: 2.3 × 10 ¹⁸ cm ⁻³ doped, thickness 0.7 μm) and p-type GaInP intermediate layer 8 (Be: 7.0 × 10 ¹⁸⁾ cm ^- Doped, the thickness 50 nm), a p-type GaAs contact layer 9 as an example of a p-type cap layer ^{(Be: 5.0 × 10 18 cm} -3 doping, 0.5 [mu] m thickness) and are sequentially formed.

The SCH-MQW active layer 4 is an MQW composed of a GaInP quantum well layer (4 layers, thickness 6 nm) and an (Al _0.50 Ga _0.50 ) InP barrier layer (3 layers, thickness 5 nm), (Al _{0 .50} Ga _0.50 ) InP guide layer (thickness 50 nm).

The p-type (Al _0.70 Ga _0.30 ) InP third cladding layer 7, the p-type GaInP intermediate layer 8, and the p-type GaAs contact layer 9 constitute a ridge 13, which is the current path of the semiconductor laser. Part of

Flat portions on both sides of the ridge 13 are formed by a GaInP etching stop layer 6, and the GaInP etching stop layer 6 is thinner than the p-type (Al _0.70 Ga _0.30 ) InP third cladding layer 7. A current blocking layer 124 is formed on the flat portion.

The current blocking layer 124 includes a p-type GaAs layer 121 (Be: 1.0 × 10 ¹⁷ cm ⁻³ doped, thickness 0.15 μm) and an n-type GaAs layer 122 (Si) formed on the p-type GaAs layer 121. : 1.0 × 10 ¹⁷ cm ⁻³ doped, thickness 0.15 μm) and an n-type GaAs layer 123 formed on the n-type GaAs layer 122 (Si: 1.0 × 10 ¹⁸ cm ⁻³ doped) And a thickness of 0.50 μm).

  A p-side electrode 10 made of Au / Mo / AuZn is formed on the current blocking layer 124 and the p-type GaAs contact layer 9. On the other hand, an n-side electrode 11 made of Au / Mo / Au / Ni / AuGe is formed on the back surface of the n-type GaAs substrate 1 (the surface opposite to the surface on the SCH-MQW active layer 4 side).

In the method of manufacturing a red semiconductor laser having the above configuration, first, an n-type GaInP buffer layer, an n-type (Al _0.70 Ga _0.30 ) InP first clad are formed on an n-type GaAs substrate using a known MBE method. layer, SCH-MQW active layer 4, p-type _{(Al 0.70 Ga} 0.30) InP second cladding layer, an undoped GaInP etching stop layer, p-type _{(Al 0.70 Ga} 0.30) InP third clad layer Then, a p-type GaInP intermediate layer and a p-type GaAs contact layer are sequentially grown.

Next, a region that becomes the ridge 13 is formed from the p-type (Al _0.70 Ga _0.30 ) InP third cladding layer, the p-type GaInP intermediate layer, and the p-type GaAs contact layer by using known photolithography and etching techniques. The part other than is selectively removed. The width of the ridge 13 is determined by the width of the etching mask used in this photolithography. Here, the width of the etching mask is set so that the width of the ridge 13 on the SCH-MQW active layer 4 side is 4.0 μm.

  Next, after a plurality of material layers for forming the current blocking layer 124 are grown (regrown) by MBE, heat treatment is performed at 740 ° C. for 30 minutes in order to improve the dopant activation rate.

  Next, an unnecessary layer grown on the region to be the ridge 13 is selectively removed by etching, and then a p-side electrode and an n-side electrode are formed, thereby completing a wafer on which a laser structure is formed.

Next, after a bar having a resonator length of 350 μm is cut out from the wafer, an Al ₂ O ₃ film is coated on the front end face and the rear end face of the bar. This Al ₂ O ₃ film is formed so that the reflectance of the front end face and the rear end face of the bar is 35%.

Finally, when a bar whose front end face and rear end face are coated with the Al ₂ O ₃ film is divided into chips, a plurality of red semiconductor lasers are obtained.

  The red semiconductor laser was attached to the SiC submount at a junction down, and the SiC submount was attached to the 5,6φ stem to complete the laser device.

  When the differential resistance value and horizontal emission angle of the red semiconductor laser were examined using the above laser apparatus, the differential resistance value was 5.7Ω and the horizontal emission angle was 9.2 degrees.

  When the red semiconductor laser was operated with no pulse-off bias and a pulse output of 3 mW, the light emission rate at a pulse width of 30 ns was 102%, which was favorable.

In the red semiconductor laser, the doping of the p-type (Al _0.70 Ga _0.30 ) InP second cladding layer 5 is higher than the doping concentration of the p-type (Al _0.70 Ga _0.30 ) InP third cladding layer 7. As a result of lowering the concentration and reducing the diffusion of the dopant into the SCH-MQW active layer 4, the threshold current Ith could be reduced to 25 mA.

  In the red semiconductor lasers of the first to third embodiments, the horizontal radiation angle may be 8.5 degrees or more, and the differential resistance value in the operating current may be 6.5 Ω or less.

  In the first to third embodiments, the ridge may be formed by four or more semiconductor layers having different band gaps.

  In the first to third embodiments, the width of the end on the active layer side of the p-type cladding layer included in the ridge may be 3.5 μm or more and 4.5 μm or less.

  In the first to third embodiments, the thickness of the cladding layer included in the ridge may be 0.6 μm or more and 0.8 μm or less.

  In the red semiconductor lasers of the first to third embodiments, the horizontal radiation angle is 8.5 degrees or more and 9.5 degrees or less, and the differential resistance value in the operating current is 6.0 Ω or less. May be.

  In the red semiconductor laser of the third embodiment, the horizontal radiation angle is 9.0 degrees or more and 9.5 degrees or less, and the differential resistance value in the operating current is 5.0Ω or more and 6.0Ω or less. It may be.

  In the first to third embodiments, the laser beam emitted from the active layer may be a single mode laser beam from the oscillation threshold value to the normal light output of 0.5 mW to 10 mW.

In the first to third embodiments, instead of the p-type (Al _0.70 Ga _0.30 ) InP third cladding layer 7, a cladding layer made of p-type AlGaInP having another Al composition ratio may be used. .

In the first to third embodiments, the p-type impurity concentration of the p-type GaInP included in the ridge is set to 5.0 × 10 ¹⁸ cm ⁻³ or more and 1.5 × 10 ¹⁹ cm ⁻³ or less, and the p included in the ridge is included. The p-type impurity concentration of the type AlGaInP may be 2.0 × 10 ¹⁸ cm ⁻³ or more and 2.5 × 10 ¹⁸ cm ⁻³ or less.

  In the first to third embodiments, after the current blocking layer is formed, heat treatment may be performed at 700 ° C. to 800 ° C. for 1 minute to 30 minutes.

  In the first and second embodiments, the carrier concentration of the cladding layer below the etching stop layer may be lower than the carrier concentration of the cladding layer on the etching stop layer.

In the first to third embodiments, a p-type cladding layer having a p-type impurity concentration of 1.5 × 10 ¹⁸ cm ⁻³ or more and 2.0 × 10 ¹⁸ cm ⁻³ or less is formed of an etching stop layer and an active layer. You may form in between.

  In the first to third embodiments, a current blocking layer having a depletion layer width of 0.30 μm or more during laser operation may be formed on both sides of the ridge.

In the first to third embodiments, even as the thickness of the carrier concentration of 2 × 10 ¹⁷ cm ^-3 or less in the region is equal to or greater than 0.30μm at a current blocking layer formed on both sides of the ridge Good.

  In the first to third embodiments, two p-type cladding layers are formed on the active layer. However, one p-type cladding layer may be formed on the active layer. In this case, a part of one p-type cladding layer formed on the active layer is included in the ridge.

  It goes without saying that the semiconductor laser of the present invention can be used in apparatuses other than laser printers.

FIG. 1 is a schematic cross-sectional view of a red semiconductor laser for a laser printer according to a first embodiment of the present invention. FIG. 2 is a schematic cross-sectional view of a red semiconductor laser for a laser printer according to a second embodiment of the present invention. FIG. 3 is a schematic cross-sectional view of a red semiconductor laser for a laser printer according to a third embodiment of the present invention. FIG. 4A is a diagram showing a variation example of the pulsed light output. FIG. 4B is a diagram illustrating another variation example of the pulsed light output. FIG. 5 is a diagram for explaining the definition of the light emission rate. FIG. 6 is a diagram for explaining the dependency of the light emission rate on the resistance value. FIG. 7 is a diagram for explaining the dependency of the light emission rate on the horizontal radiation angle.

Explanation of symbols

1 n-type GaAs substrate 2 n-type GaInP buffer layer 3 n-type (Al _0.70 Ga _0.30 ) InP first cladding layer 4 SCH-MQW active layer 4
5 p-type (Al _0.70 Ga _0.30 ) InP second cladding layer 6 GaInP etching stop layer 7 p-type (Al _0.70 Ga _0.30 ) InP third cladding layer 8 p-type GaInP intermediate layer 9 p-type GaAs contact layer 10 p-side electrode 11 n-side electrode 12 n-type GaAs current blocking layer 13 ridge 121 p-type GaAs layers 122 and 123 n-type GaAs layer 124 current blocking layer

Claims (14)

An active layer,
A p-type cladding layer formed directly or indirectly on the active layer;
A p-type cap layer formed on the p-type cladding layer via a semiconductor layer,
A current path from the p-type cap layer to the p-type cladding layer has a striped ridge formed of at least three semiconductor layers having different band gaps;
The horizontal radiation angle is 8.5 degrees or more, and the differential resistance value at the operating current is 6.5 Ω or less,
A semiconductor laser that emits red laser light and is AlGaInP-based. The semiconductor laser according to claim 1, wherein
A semiconductor laser characterized in that the radiation angle is 9.0 degrees or more and the differential resistance value is 5.0Ω or more. The semiconductor laser according to claim 1, wherein
A semiconductor laser, wherein a width of an end of the p-type cladding layer on the active layer side is 3.5 μm or more and 4.5 μm or less. The semiconductor laser according to claim 3, wherein
The ridge includes the p-type cladding layer;
The p-type cladding layer has a thickness of 0.6 μm or more and 0.8 μm or less. The semiconductor laser according to claim 1, wherein
A semiconductor laser, wherein the radiation angle is 9.5 degrees or less and the differential resistance value is 6.0 Ω or less. The semiconductor laser according to claim 1, wherein
A semiconductor laser, wherein the radiation angle is 9.0 degrees or more and 9.5 degrees or less, and the differential resistance value is 5.0 Ω or more and 6.0 Ω or less. The semiconductor laser according to claim 1, wherein
2. The semiconductor laser according to claim 1, wherein the laser beam is a single mode laser beam from an oscillation threshold value to a normal light output of 0.5 mW to 10 mW. The semiconductor laser according to claim 1, wherein
A semiconductor laser characterized in that the current path is composed of p-type GaAs, p-type GaInP, and p-type AlGaInP. The semiconductor laser according to claim 8, wherein
The p-type impurity concentration of the p-type GaInP is 5.0 × 10 ¹⁸ cm ⁻³ or more and 1.5 × 10 ¹⁹ cm ⁻³ or less,
A semiconductor laser, wherein the p-type impurity concentration of the p-type AlGaInP is 2.0 × 10 ¹⁸ cm ⁻³ or more and 2.5 × 10 ¹⁸ cm ⁻³ or less. The semiconductor laser according to claim 9, wherein
A semiconductor laser manufactured by performing heat treatment at 700 ° C. to 800 ° C. for 1 minute to 30 minutes. The semiconductor laser according to claim 1, wherein
A semiconductor laser comprising a p-type cladding layer formed between the active layer and the p-type cladding layer and having a carrier concentration lower than that of the p-type cladding layer. The semiconductor laser according to claim 11, wherein
A semiconductor laser, wherein the p-type cladding layer having a low carrier concentration has a p-type impurity concentration of 1.5 × 10 ¹⁸ cm ⁻³ or more and 2.0 × 10 ¹⁸ cm ⁻³ or less. The semiconductor laser according to claim 1, wherein
A semiconductor laser comprising a current blocking layer formed on both sides of the ridge and having a depletion layer width of 0.30 μm or more during laser operation. The semiconductor laser according to claim 13, wherein
A semiconductor laser, wherein a thickness of a region having a carrier concentration of 2 × 10 ¹⁷ cm ⁻³ or less in the current blocking layer is 0.30 μm or more.

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