JPH06112586A - Semiconductor laser diode - Google Patents

Abstract

PURPOSE:To enhance high output operation characteristics of semiconductor laser diode by making an active layer sufficiently thin thereby enhancing controllability of impurity diffusion step. CONSTITUTION:The semiconductor laser diode comprises a multilayer epitaxial layer 2 including at least n-AlGaAsInP clad layer 9, an active layer 11 of GaInP or AlGaInP, and a P-AlGaInP clad layer 13 formed sequentially on an n-GaAs substrate 7, and a pair of laser edges 6. The active layer 11 or the P-AlGaInP clad layer 13 is formed sufficiently thin and the active layer 11 in the pumping region 3 of the laser is composed of AlGaInP in ordered state whereas the active layer 11 in the window region 4 in the vicinity of the laser edge 6 is composed of AlGaInP in disorded State. The active layer 11 is a multiple quantum well layer of 50nm thick or less. Alternatively, a GaInP well layer in disordered state may be employed. Furthermore, the P-AlGaInP clad layer 13 is set at 0.75mum thick or less.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high power semiconductor laser used as a light source for an information processing device such as an optical disk device.

[0002]

2. Description of the Related Art In recent years, in order to further increase the recording capacity of an optical disk device, development of a visible light semiconductor laser having an oscillation wavelength shorter than before has been underway. In order for the visible light semiconductor laser to perform the high output operation necessary for the optical disk device,
Optical damage due to absorption of light near the facet of the visible light semiconductor laser must be suppressed. Recently, Ueno et al. (Japanese Journal of Applied Physics Vol. 29, No. 9, L1666-L1668, September 1990) and Itaya et al. (The 12th IEEE International Laser Diode International Conference, September 1990, Davos, Switzerland, Lecture number C-5) prototyped a window-type visible light semiconductor laser having an active layer with a large bandgap energy near the laser facet, and showed that optical damage was suppressed, and reported excellent high-power operating characteristics. The semiconductor laser inside the active layer is Ga _0.5 In _0.5 P (thickness 60nm large disordered state of the active layer band gap energy of the laser facet vicinity whereas consisting Ga _0.5 In _0.5 P of ordered state (thickness 60nm) ), The light absorption near the laser end face was reduced. The disordered GaInP active layer was formed by diffusing impurities into the disordered GaInP active layer. The impurities diffused into the active layer from the surface of the clad layer (thickness 1 μm) located on the side opposite to the substrate with respect to the active layer, through the inside.

[0003]

When the impurity concentration of the GaInP active layer is insufficient, the GaInP in the ordered state remains and the light absorption is not sufficiently reduced. On the other hand, when the GaInP active layer has an excessive impurity concentration, light absorption increases due to free carrier scattering and increase in band tail. Therefore, the impurity concentration of the active layer needs to be appropriately controlled. The above-mentioned conventional semiconductor laser has insufficient control of the impurity concentration, and its high-power operation characteristics are limited. In order to improve the high output operation characteristics of the semiconductor laser, it is necessary to improve the controllability of the impurities.

[0004]

One of the semiconductor lasers of the present invention is a semiconductor laser characterized in that the thickness of the active layer is as thin as 50 nm or less. Another semiconductor laser of the present invention is a semiconductor laser characterized in that the thickness of the clad layer located on the side opposite to the substrate with respect to the active layer is as thin as 0.75 μm or less.

[0005]

When the impurities diffuse into the active layer through the clad layer, an impurity concentration gradient occurs from the upper end of the active layer to the lower end. The thinner the active layer is, the smaller the difference in impurity concentration between the upper end and the lower end of the active layer is, and the controllability of the impurity concentration over the entire active layer is improved. Further, since the impurities diffuse from the surface of the clad layer to the upper end of the active layer, the thinner the clad layer, the shorter the diffusion distance of the impurity and the better the controllability of the impurity in the active layer.

[0006]

1 is a plan view of a semiconductor laser of the present invention. The active layer of the pumping region 3 inside the laser is Al with an ordered state.
While it is made of GaInP, the active layer in the window region 4 near the laser end face 6 is made of disordered AlGaInP. 2 and 3 are laser sectional views in the excitation region 3 and the window region 4, respectively. The cross sections of FIGS. 2 and 3 are planes parallel to the laser end face 6 of FIG.

One of the embodiments of the semiconductor laser of the present invention will be shown below. First, on the n-GaAs substrate 7, n-GaAs
Buffer layer 8, 900 nm thick Si-doped n- (Al
_0.7 Ga _0.3 ) _0.5 In _0.5 P clad layer 9, 100n
m-thick Si-doped n- (Al _0.6 Ga _0.4 ) _0.5 In
_0.5 P guide layer 10, active layer 11, 100 nm thick Zn
Doped p- (Al _0.6 Ga _0.4 ) _0.5 In _0.5 P guide layer 12, 900 nm thick Zn-doped p- (Al _0.7 Ga
_0.3 ) _0.5 In _0.5 P clad layer 13, 10 nm thick Z
The n-doped p-Ga _0.5 In _0.5 P layer 14 is sequentially formed by metalorganic vapor phase epitaxy (Metalorganic Vapor Deposition).
Phase epitaxy: MOVPE method). The crystal growth condition is a growth temperature of 650-750.
C, V / III ratio 50-500, growth rate 1-2 μm /
It was set to h. The crystal growth method is not limited to the MOVPE method but MBE
Method, MOMBE method, GSMBE method and the like. The active layer 11 has a thickness of 10 nm and is in a disordered state (Al _0.05 G
a _0.95 ) _0.5 In _0.5 P well layer and 5 nm thick (Al
_This is a multiple quantum well layer composed of a _0.6 Ga _0.4 ) _0.5 In _0.5 P barrier layer. Disordered (Al _0.05 Ga _0.95 )
The band gap energy of _0.5 In _0.5 P is 1.88.
eV. The number of wells was 4. Disordered Ga
An InP well layer may be used. 50n in the active layer 11
Disordered AlGaInP or Ga with thickness less than m
An InP bulk layer may be used. p-GaInP layer 14
P-AlGaInP clad layer 1 after crystal growth up to
3 and a part of the p-GaInP layer 14 were removed to form a mesa-shaped stripe having a width of 3-6 μm, and the optical waveguide 1 was formed. Next, Zn impurities were diffused from the surface of the p-GaInP layer 14 in the window region 4 to the active layer 11 through the p-AlGaInP clad layer 13 and the p-AlGaInP guide layer 12. The impurity diffusion was performed by a thermal diffusion method using a ZnAs2 diffusion raw material and a diffusion mask, and the diffusion temperature was 600 to 700 ° C. and the diffusion time was less than 1 hour. The diffusion material is not limited to ZnAs2, but Zn2As3 or the like may be used. The impurity diffusion is not limited to the thermal diffusion method, but the self-diffusion phenomenon of Dopan Zn during crystal growth (12th IEEE International Semiconductor Laser International Conference, September 1990, Davos, Switzerland,
You may use the lecture number C-5). When the diffusion of the incombustibles is completed, the AlGaInP in the window region 4 is
The well layer is in a disordered state. The bandgap energy of the disordered well layer is about 1.95 eV.
As a result of improving the controllability of the impurity diffusion, the light absorption of the active layer in the window region was significantly reduced. After impurity diffusion,
The n-GaAs block layer 15 was selectively grown, and the p-GaAs contact layer 16 was further grown on the entire surface to form an n electrode 17 and ap electrode 18. Finally, the laser end face 6 was formed by cleavage, and a dielectric film having a single emissivity and a high reflectance was formed on each of the laser end faces to complete a semiconductor laser. The resonator length was 700 μm. Since the semiconductor laser includes the guide layer, the oscillation threshold current is as low as 60 mA even though the active layer 11 is thin. Spot size d / Γ
Is 0.32 μm, which is almost equal to that of a conventional semiconductor laser. The semiconductor laser operated stably at an output of 50 mW for a long time.

Next, a second embodiment of the semiconductor laser of the present invention will be shown below. Since the structure and manufacturing method of this embodiment have many similarities to the first embodiment already described, only the points different from the first embodiment will be described below with reference to FIGS. 2 and 3. First, the n- (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P cladding layer 9 was thickened to 3 μm, and n- (Al _0.6 G 3
The a _{0. 4) 0.5} In _0.5 P guiding layer 10 was set to 300 nm. The number of wells in the multiple quantum well active layer 11 was set to 6. p
The -AlGaInP guide layer 12 is not used. p- (Al
_{The 0.7} Ga _0.3 ) _0.5 In _0.5 P layer 13 was thinned to 650 nm. Since a thick guide layer is provided on the n side, the p-AlG
Although the aInP clad layer 13 is thin, p-Ga
Light seeping into the As contact layer 16 is small, and
The mode loss based on the light absorption of As is as small as 8 cm-1. The spot size d / Γ of this semiconductor laser is 0.30
It was as small as μm, and the oscillation threshold current was as low as 60 mA. The semiconductor laser operated stably at an output of 50 mW for a long time.

[0009]

According to the present invention, it is possible to enhance the controllability of the impurity diffusion step required for manufacturing a semiconductor laser and improve the high output operation characteristics of the semiconductor laser.

[Brief description of drawings]

FIG. 1 is a diagram showing a planar structure of a semiconductor laser of the present invention.

FIG. 2 is one of the views showing the cross-sectional structure of the semiconductor laser of the present invention.

FIG. 3 is another diagram showing the cross-sectional structure of the semiconductor laser of the present invention.

[Explanation of symbols]

 1 Optical Waveguide 4 Window Area 6 Laser End Face 7 n-GaAs Substrate 9 n-AlGaInP Clad Layer 10 n-AlGaInP Guide Layer 11 Active Layer 12 p-AlGaInP Guide Layer 13 p-AlGaInP Clad Layer 15 n-GaAs Block Layer 16 p- GaAs contact layer

Claims (4)

[Claims] 1. A multilayer including at least a first-conductivity-type AlGaAsInP clad layer sequentially formed on a first-conductivity-type GaAs substrate, an active layer made of GaInP or AlGaInP, and a second-conductivity-type AlGaInP clad layer. An epitaxial layer and a pair of laser end faces are provided, and the active layer or the second conduction type clad layer is sufficiently thin, the active layer near the laser end face is in a disordered state, and the active layer inside the laser is A semiconductor laser characterized by being in an ordered state. 2. The active layer comprises AlGaInP and Ga.
2. A multiple quantum well layer made of InP, wherein the total thickness of the well layers is 50 nm or less.
The semiconductor laser described in 1. 3. The active layer is Ga having a thickness of 50 nm or less.
The semiconductor laser according to claim 1, wherein the semiconductor laser comprises an InP or AlGaInP bulk layer. 4. The second conductivity type cladding layer has a thickness of 0.75.
The semiconductor laser according to claim 3, wherein the semiconductor laser has a thickness of not more than μm.