CN103326242B - Laser active district, semiconductor laser and preparation method thereof - Google Patents

Abstract

The invention discloses a kind of semiconductor laser active area, described active area comprises a multi-quantum pit structure, in described multi-quantum pit structure, the material of potential well layer is InGaAsP, in described quantum well structure, the material of barrier layer is InGaAlAs, the periodicity of described multi-quantum pit structure is the scope of K, K is 3 ~ 20, and, the invention also discloses a kind of semiconductor laser and preparation method thereof, this semiconductor laser comprises aforesaid active area.Semiconductor laser provided by the invention has lower threshold current, higher characteristic temperature, can realize without refrigeration work; There is the higher differential gain, TM Mode for Laser can be provided to export; There is larger conduction band band rank ratio, can realize effectively limiting and charge carrier being uniformly distributed between trap injection charge carrier simultaneously, improve laser modulation characteristic.

Description

Laser active region, semiconductor laser and manufacturing method thereof

technical field

The invention relates to the field of semiconductor optoelectronics, in particular to an active region of a laser, a semiconductor laser including the active region and a manufacturing method thereof.

Background technique

In the field of high-speed optical fiber communication, 1310nm InGaAsP/InP strained quantum well lasers have been extensively and deeply studied. Theory predicts that compared with lattice matching and compressive strain quantum wells, the transverse magnetic field (TM) mode gain provided by the tensile strain quantum well exceeds the transverse electric field (TE) mode gain provided by the compressive strain quantum well, and the tensile strain quantum well can obtain more Optimal device performance, such as lower threshold current, higher differential gain and smaller Auger recombination rate, etc.

At present, the commercialized 1310nm semiconductor laser is mainly based on the InGaAsP/InP material system. However, it is still difficult for the InGaAsP/InP laser to work at a temperature above 85°C without refrigeration. In order to solve this problem, another alternative material system that covers the optical band centered at 1310nm is being developed is InGaNAs/GaAs. So far, it is still difficult to increase the N component to 10% for the InGaNAs/GaAs material system. And doping N atoms is easy to introduce defects, so the laser based on this material system is still in its infancy.

Contents of the invention

Aiming at the deficiencies of the prior art mentioned above, the present invention proposes a laser active region and a semiconductor laser including the active region, the semiconductor laser can realize effective confinement and current-carrying of injected carriers at the same time The homogeneous distribution of subs in the active area has lower threshold current and higher differential gain, has lower Auger recombination rate and can realize cooling-free operation.

In order to achieve the above object, the present invention adopts the following technical solutions:

Provide a kind of laser active area, described active area comprises a multi-quantum well structure, the material of the potential well layer in the described multi-quantum well structure is InGaAsP, the material of the potential barrier layer in the described quantum well structure is InGaAlAs, so The period number of the multi-quantum well structure is K, and the range of K is 3-20.

Preferably, the active region is P-type doped.

Preferably, in the material In _1-x Ga _x As _y P _1-y of the potential well layer, x=51%, y=79%, with 1% tensile strain; the material In ₁ -x of the barrier layer In _xy Ga _x Al _y As, x = 11.2%, y = 28.8%, with 0.5% compressive strain.

Preferably, the potential well layer has a thickness of 6-10 nm, and the barrier layer has a thickness of 10-20 nm.

Preferably, the number of periods of the multi-quantum well structure is six.

The present invention also provides a semiconductor laser comprising the active region as described above.

Preferably, the semiconductor laser includes a substrate, a first transition layer, a first confinement layer, a first waveguide layer, the active region, a second waveguide layer, a second confinement layer, and a second transition layer that are sequentially stacked. and ohmic contact layers.

Preferably, the material of the substrate is InP, the material of the first transition layer and the second transition layer is InGaAlAs, the material of the first confinement layer and the second confinement layer is InAlAs, and the first waveguide layer and the material of the second waveguide layer is InGaAlAs, and the material of the ohmic contact layer is InGaAs.

Preferably, the material of the substrate is N-type InP; the material of the first transition layer In _1-xy Ga _x Al _y As adopts an N-type doped structure with a graded composition, wherein (1-xy) = 53%, y gradually changes from 39% to 47% in the direction away from the substrate; the material of the first confinement layer is In _x Al _1-x As using an N-type doped structure, where x = 53% ; The material In _1-xy Ga _{x Aly} As of the first waveguide layer adopts a non-doped, composition graded structure, wherein, (1-xy)=53%, y changes from 47% gradually changed to 28.8%; the material In _1-xy Ga _x Al _y As of the second waveguide layer adopts P-type doping and composition graded structure, wherein, (1-xy)=53%, y is according to the distance The direction of the substrate gradually changes from 28.8% to 47%; the material of the second confinement layer In _x Al _1-x As adopts a P-type doped structure, where x=53%; the second transition layer The material In _1-xy Ga _{x Aly} As adopts P-type doping and composition gradient structure, wherein (1-xy)=53%, and y gradually changes from 47% to 39% in the direction away from the substrate ; The material of the ohmic contact layer, InGaAs, adopts a P-type doped structure.

Another object of the present invention is also to provide a method for manufacturing a semiconductor laser as described above, comprising the steps of:

1. The following structural layers are sequentially grown by MOCVD process or MBE process:

a) growing a first transition layer of InGaAlAs on an InP substrate;

b) InAlAs first confinement layer;

c) InGaAlAs first waveguide layer;

d) Active area:

d1) InGaAlAs barrier layer;

d2) InGaAsP potential well layer;

e) repeating step d1) and step d2), until the active region of the multi-quantum well structure with K periods is grown, wherein the range of K is 3-20;

f) InGaAlAs second waveguide layer;

g) InAlAs second confinement layer;

h) InGaAlAs second transition layer;

i) InGaAs ohmic contact layer.

Wherein, the material of the substrate is N-type InP; the material In _1-xy Ga _{x Aly} As of the first transition layer adopts an N-type doped structure with a graded composition, wherein (1-xy)= 53%, y gradually changes from 39% to 47% in the direction away from the substrate; the material of the first confinement layer is In _x Al _1-x As using an N-type doped structure, where x=53%; The material of the first waveguide layer, In _1-xy Ga _{x Aly} As, adopts a non-doped, composition-graded structure, where (1-xy)=53%, and y changes from 47 to 47 in the direction away from the substrate. % is gradually changed to 28.8%; the material of the second waveguide layer, In _1-xy Ga _{x Aly} As, adopts a P-type doped structure with a graded composition, wherein (1-xy)=53%, and y is based on distance from the The direction of the substrate is gradually changed from 28.8% to 47%; the material of the second confinement layer In _x Al _1-x As adopts a P-type doped structure, where x=53%; the second transition layer The material In _1-xy Ga _{x Aly} As adopts a structure of P-type doping and graded composition, wherein (1-xy)=53%, and y is graded from 47% to 39% in the direction away from the substrate; The material of the ohmic contact layer, InGaAs, adopts a P-type doped structure.

2. After the growth of each structural layer is completed, the dielectric film is first evaporated by electron beams, and then the P-type electrode window is formed through conventional photolithography and corrosion processes, and Au/Zn/Au is thermally evaporated to form a P-type ohmic contact electrode; The InP substrate surface is chemically thinned and evaporated Au/Ge/Ni to form an N-type ohmic contact layer; finally, a laser chip is formed by cleavage, and then the chip is sintered to a heat sink, and leads are connected to obtain the semiconductor laser.

Using InGaAlAs material as the barrier layer and InGaAsP material as the well layer can not only obtain a large conduction band step ratio (ΔE _c ≈ 0.72ΔE _g ), suppress electron overflow, but also obtain a very uniform well with weak confinement of holes distributed among them, resulting in lower threshold current and higher gain. InGaAsP/InGaAlAs tensile strain quantum well can provide TM mode laser output, further reduce threshold current, increase differential gain and have smaller Auger recombination rate. In addition, the P-type doping of the active region is helpful for hole transport, and higher differential gain can be obtained, which is beneficial to improve the modulation characteristics of the device. Therefore, the P-type doped InGaAsP/InGaAlAs tensile strain quantum well has become the preferred material for the active region of the 1310nmTM high-speed laser.

Compared with the prior art, the present invention has the following advantages:

1. The present invention adopts the InGaAsP/InGaAlAs material system to make the tensile strain quantum well structure as the laser as the active region, and the laser including the active region has a lower threshold current, a higher characteristic temperature, and can realize non-refrigerated work; High differential gain, can provide TM mode laser output; has a large conduction band step ratio, can realize effective confinement of injected carriers and uniform distribution of carriers between wells at the same time, and improve laser modulation characteristics ;

2. The active region of the multi-quantum well structure provided by the present invention adopts the design of the strain compensation quantum well structure and the heavy hole energy level alignment between the well and the barrier—even if the heavy hole energy level between the well and the barrier is at the same energy position , can reduce the threshold current, improve slope efficiency and modulation bandwidth;

3. The active region of the multi-quantum well structure provided by the present invention adopts P-type doping, so that the carriers are more evenly distributed among the wells, the modulation bandwidth can be expanded, and the modulation characteristics of the laser can be improved;

4. The semiconductor laser provided by the present invention introduces graded transition layers between the substrate and the confinement layer and between the ohmic contact layer and the confinement layer, which can make the electric field distribution more gentle and improve the carrier injection efficiency.

Description of drawings

FIG. 1 is a schematic diagram of the structure of an active region of a laser prepared in an embodiment of the present invention.

Fig. 2 is a schematic structural diagram of a semiconductor laser prepared in an embodiment of the present invention.

detailed description

The present invention will be further described below with reference to the accompanying drawings.

As mentioned above, in view of the deficiencies in the prior art, the present invention proposes a laser active region and a semiconductor laser including the active region, the semiconductor laser can achieve effective confinement of injected carriers and Uniform distribution of carriers in the active region, lower threshold current and higher differential gain, lower Auger recombination rate and cooling-free operation.

The laser active region includes a multi-quantum well structure, the material of the potential well layer in the multi-quantum well structure is InGaAsP, the material of the barrier layer in the quantum well structure is InGaAlAs, and the period number of the multi-quantum well structure is is K, the range of K is 3-20, the thickness of the potential well layer is 6-10 nm, and the thickness of the barrier layer is 10-20 nm.

Specifically, this embodiment will take an active region with a 6-period multi-quantum well structure as an example for detailed description.

As shown in Figure 1, the active region 07 is composed of a 6-period multi-quantum well structure, including 7 barrier layers 05 and 6 potential well layers 06 alternately stacked; the material of the potential well layer 06 is In In _1-x Ga _x As _y P _1-y , x=51%, y=79%, with 1% tensile strain; in the material In _1-xy Ga _x Al _y As of the barrier layer 05, x= 11.2%, y=28.8%, with 0.5% compressive strain; wherein, the thickness of each potential well layer 06 is 10nm, and the thickness of each potential barrier layer 05 is 20nm; the material of the potential well layer 06 is InGaAsP and the potential barrier layer 05 The materials InGaAlAs are all P-type doped.

In this embodiment, the active region of the multi-quantum well structure adopts P-type doping, so that the distribution of carriers among the wells is more uniform, the modulation bandwidth can be expanded, and the modulation characteristics of the laser can be improved.

This embodiment also provides a semiconductor laser, which includes the above-mentioned active region. Specifically, as shown in FIG. 2, the semiconductor laser includes an InP substrate 01, an InGaAlAs first transition layer 02, an InAlAs first confinement layer 03, an InGaAlAs first waveguide layer 04, and the above-mentioned active Region 07 , InGaAlAs second waveguide layer 08 , InAlAs second confinement layer 09 , InGaAlAs second transition layer 10 and InGaAs ohmic contact layer 11 .

Wherein, the material of the substrate 01 is N-type InP; the material In _1-xy Ga _x Al _y As of the first transition layer 02 adopts an N-type doped structure with a graded composition, wherein (1-xy )=53%, y gradually changes from 39% to 47% according to the direction away from the substrate 01; the material In _x Al _1-x As of the first confinement layer 03 adopts an N-type doped structure, wherein, x =53%; the material In _1-xy Ga _{x AlyAs} of the first waveguide layer 04 adopts a non-doped, composition-graded structure, wherein, (1-xy)=53%, y according to the distance from the substrate The direction of the bottom 01 is gradually changed from 47% to 28.8%; the material In _1-xy Ga _x Al _y As of the second waveguide layer 08 adopts a P-type doped structure with a graded composition, where (1-xy)= 53%, y gradually changes from 28.8% to 47% in the direction away from the substrate 01; the material of the second confinement layer 09 is In _x Al _1-x As with a P-type doped structure, where x=53 %; the material In _1-xy Ga _{x Aly} As of the second transition layer 10 adopts a P-type doped, composition graded structure, wherein, (1-xy)=53%, y according to far away from the substrate The direction of 01 gradually changes from 47% to 39%; the material of the ohmic contact layer 11 is InGaAs with a P-type doped structure.

In the semiconductor laser provided by this embodiment, graded transition layers are respectively introduced between the substrate and the confinement layer and between the ohmic contact layer and the confinement layer, which can make the electric field distribution more gentle and improve the carrier injection efficiency.

The manufacturing method of the above-mentioned semiconductor laser is introduced below, and the method specifically includes steps:

1. The following structural layers are sequentially grown by MOCVD process or MBE process:

(1) On the N-type InP substrate 01, a 0.1 μm-thick InGaAlAs first transition layer 02 with an N-type doping concentration of about 1×10 ¹⁸ cm ^-3 and a graded composition is grown, and the In _1-xy Ga _x Al _y As in the first transition layer 02, the composition of In (1-xy)=53%, and the composition y of Al gradually changes from 39% to 47% in the direction away from the substrate 01;

(2) grow a 0.4 μm thick InAlAs first confinement layer 03 with an N-type doping concentration of about 1×10 ¹⁸ cm ^-3 , and in the In _x Al _1-x As first confinement layer 03 , the composition of In is x = 53%;

(3) growing a 0.15 μm thick non-doped, composition graded InGaAlAs first waveguide layer 04, in the In _1-xy Ga _x Al _y As first waveguide layer 04, the composition of In (1-xy) =53%, the composition y of Al gradually changes from 47% to 28.8% in the direction away from the substrate 01;

(4) Alternately grow 20nm-thick InGaAlAs barrier layer 05 with a P-type doping concentration of 3×10 ¹⁷ cm ^-3 (7 layers in total) and 10nm-thick InGaAsP with a P-type doping concentration of 3×10 ¹⁷ cm ^-3 Potential well layer 06 (totally 6 layers), forms the active region 07 that has 6 periodic multi-quantum well structures; Wherein, in the material In _1-x Ga _x As _y P _1-y of described potential well layer 06, x= 51%, y=79%, with 1% tensile strain; in the material In _1-xy Ga _x Al _y As of the barrier layer 05, x=11.2%, y=28.8%, with 0.5% compressive strain;

(5) Grow a 0.15 μm-thick second waveguide layer 08 of InGaAlAs with a P-type doping concentration of 3×10 ¹⁷ cm ^-3 and a graded composition. The second waveguide layer 08 of In _1-xy Ga _x Al _y As Among them, the composition of In (1-xy)=53%, the composition y of Al gradually changes from 28.8% to 47% in the direction away from the substrate 01;

(6) grow a 0.4 μm thick InAlAs second confinement layer 09 with a P-type doping concentration of about 1×10 ¹⁸ cm ^-3 , and in the In _x Al _1-x As second confinement layer 09 , the composition of In x = 53%;

(7) growing a 0.1 μm thick InGaAlAs second transition layer 10 with a P-type doping concentration of about 1×10 ¹⁸ cm ^-3 and a graded composition, the In _1-xy Ga _x Al _y As second transition layer 10 Among them, the composition of In (1-xy)=53%, and the composition y of Al gradually changes from 47% to 39% in the direction away from the substrate 01;

(8) A 0.2 μm thick InGaAs ohmic contact layer 11 with a P-type doping concentration of about 2×10 ¹⁹ cm ⁻³ is grown.

2. After the growth of each structural layer is completed, a 0.1 μm thick SiO ₂ dielectric film is first evaporated by an electron beam, and then a P-type electrode window (200 μm in width) is formed through a conventional photolithography and etching process, and Au/Zn is thermally evaporated /Au to form a P-type ohmic contact electrode; use chemical thinning on the InP substrate surface to about 100 μm and evaporate Au/Ge/Ni to form an N-type ohmic contact layer; finally cleavage to form a laser chip, and then sinter the chip to a heat sink On, connect the leads to obtain the semiconductor laser.

In the above-mentioned embodiments, each step is grown by MOCVD (MetalOrganicChemicalVaporDeposition, metal organic compound chemical vapor deposition) or MBE (MolecularBeamEpitaxy, molecular beam epitaxy); if the MOCVD process is used, the N-type dopant atoms of each layer are Si, Se, S or Te, the P-type dopant atoms are Zn, Mg or C; if the MBE process is adopted, the N-type dopant atoms of each layer are Si, Se, S, Sn or Te, and the P-type dopant atoms are Be, Mg or c.

The present invention adopts the InGaAsP/InGaAlAs material system to make the tensile strain quantum well structure as the laser as the active region, adopts the strain compensation quantum well structure and the design of heavy hole energy level alignment between the well and the barrier—even if the heavy hole between the well and the barrier The energy level of the hole is at the same energy position, which can reduce the threshold current, improve the slope efficiency and modulation bandwidth; the laser containing the active region has a lower threshold current, a higher characteristic temperature, and can realize no cooling operation; it has a higher Differential gain can provide TM mode laser output; it has a large conduction band step ratio, which can realize effective confinement of injected carriers and uniform distribution of carriers between wells at the same time, improving laser modulation characteristics.

It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is a relationship between these entities or operations. any such actual relationship or order exists between them. Furthermore, the term "comprises", "comprises" or any other variation thereof is intended to cover a non-exclusive inclusion such that a process, method, article, or apparatus comprising a set of elements includes not only those elements, but also includes elements not expressly listed. other elements of or also include elements inherent in such a process, method, article, or device. Without further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of additional identical elements in the process, method, article or apparatus comprising said element.

The above description is only the specific implementation of the present application. It should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present application, some improvements and modifications can also be made. It should be regarded as the protection scope of this application.

Claims (12)

1. a laser active district, it is characterized in that: described active area comprises a multi-quantum pit structure, in described multi-quantum pit structure, the material of potential well layer is InGaAsP, in described multi-quantum pit structure, the material of barrier layer is InGaAlAs, the periodicity of described multi-quantum pit structure is the scope of K, K is 3 ~ 20; Wherein, the material In of described potential well layer _1-xga _xas _yp _1-yin, x=51%, y=79%, have 1% tensile strain; The material In of described barrier layer _1-x-yga _xal _yin As, x=11.2%, y=28.8%, have 0.5% compressive strain.

2. laser active district according to claim 1, is characterized in that: described active area is the doping of P type.

3. laser active district according to claim 1, it is characterized in that: the thickness of described potential well layer is 6 ~ 10nm, the thickness of described barrier layer is 10 ~ 20nm.

4. laser active district according to claim 1, is characterized in that: the periodicity of described multi-quantum pit structure is 6.

5. a semiconductor laser, is characterized in that: comprise as arbitrary in claim 1-4 as described in active area.

6. semiconductor laser according to claim 5, is characterized in that: this semiconductor laser comprises substrate that lamination successively arranges, First Transition layer, the first limiting layer, first wave conducting shell, described active area, Second Wave conducting shell, the second limiting layer, the second transition zone and ohmic contact layer.

7. semiconductor laser according to claim 6, it is characterized in that: the material of described substrate is InP, the material of described First Transition layer and the second transition zone is InGaAlAs, the material of described first limiting layer and the second limiting layer is InAlAs, the material of described first wave conducting shell and Second Wave conducting shell is InGaAlAs, and described ohmic contact layer is material is InGaAs.

8. semiconductor laser according to claim 7, is characterized in that:

The material of described substrate is N-type InP;

The material In of described First Transition layer _1-x-yga _xal _yas adopts the structure of N-type doping, content gradually variational, and wherein, (1-x-y)=53%, y is gradient to 47% according to the direction away from described substrate from 39%;

The material In of described first limiting layer _xal _1-xas adopts the structure of N-type doping, wherein, and x=53%;

The material In of described first wave conducting shell _1-x-yga _xal _yas adopts the structure of undoped, content gradually variational, and wherein, (1-x-y)=53%, y is gradient to 28.8% according to the direction away from described substrate from 47%;

The material In of described Second Wave conducting shell _1-x-yga _xal _yas adopts the structure of the doping of P type, content gradually variational, and wherein, (1-x-y)=53%, y is gradient to 47% according to the direction away from described substrate from 28.8%;

The material In of described second limiting layer _xal _1-xas adopts the structure of P type doping, wherein, and x=53%;

The material In of described second transition zone _1-x-yga _xal _yas adopts the structure of the doping of P type, content gradually variational, and wherein, (1-x-y)=53%, y is gradient to 39% according to the direction away from described substrate from 47%;

The material of described ohmic contact layer is P type InGaAs.

9. a manufacture method for semiconductor laser as claimed in claim 7, is characterized in that:

Comprise step: adopt MOCVD technique or MBE technique to grow following each structure sheaf successively:

A) in InP substrate, grow InGaAlAs First Transition layer;

B) InAlAs first limiting layer;

C) InGaAlAs first wave conducting shell;

D) active area:

D1) InGaAlAs barrier layer;

D2) InGaAsP potential well layer;

E) steps d 1 is repeated) and steps d 2), until grown the active area of the multi-quantum pit structure with K cycle, wherein the scope of K has been 3 ~ 20;

F) InGaAlAs Second Wave conducting shell;

G) InAlAs second limiting layer;

H) InGaAlAs second transition zone;

I) InGaAs ohmic contact layer.

10. the manufacture method of semiconductor laser according to claim 9, is characterized in that:

The material InP of described substrate adopts the structure of N-type doping;

The material In of described First Transition layer _1-x-yga _xal _yas adopts the structure of N-type doping, content gradually variational, and wherein, (1-x-y)=53%, y is gradient to 47% according to the direction away from described substrate from 39%;

The material In of described first limiting layer _xal _1-xas adopts the structure of N-type doping, wherein, and x=53%;

The material In of described first wave conducting shell _1-x-yga _xal _yas adopts the structure of undoped, content gradually variational, and wherein, (1-x-y)=53%, y is gradient to 28.8% according to the direction away from described substrate from 47%;

The material In of described Second Wave conducting shell _1-x-yga _xal _yas adopts the structure of the doping of P type, content gradually variational, and wherein, (1-x-y)=53%, y is gradient to 47% according to the direction away from described substrate from 28.8%;

The material In of described second limiting layer _xal _1-xas adopts the structure of P type doping, wherein, and x=53%;

The material In of described second transition zone _1-x-yga _xal _yas adopts the structure of the doping of P type, content gradually variational, and wherein, (1-x-y)=53%, y is gradient to 39% according to the direction away from described substrate from 47%;

The material InGaAs of described ohmic contact layer adopts the structure of P type doping.

11. according to claim 9 or 10 manufacture method of semiconductor laser, it is characterized in that: the method also comprises following technique: after completing each structure sheaf of growth, first by electron beam evaporation deielectric-coating, P-type electrode window is formed again through conventional photoetching, etching process, and thermal evaporation Au/Zn/Au, form P type Ohm contact electrode; After InP substrate face adopts chemical reduction, evaporate Au/Ge/Ni, form N-type ohmic contact layer; Last cleavage forms chip of laser, then chip is sintered to heat sink on, connecting lead wire, obtains described semiconductor laser.

12. according to claim 9 or 10 manufacture method of semiconductor laser, it is characterized in that: the periodicity of described multi-quantum pit structure is 6.