Vertical cavity surface emitting laser and laser array

Abstract

The vertical cavity surface emitting laser comprises a substrate, a first DBR layer, a quantum well active region, an oxide layer and a second DBR layer which are sequentially stacked from bottom to top, the quantum well active region comprises InGaAs potential well layers and InGaP barrier layers which are alternately arranged, each InGaAs potential well layer is inserted between two adjacent InGaP barrier layers, and the InGaAs potential well layers and the InGaP barrier layers are alternately arranged. The number of the InGaAs potential well layers is m, m is larger than or equal to 3 and smaller than or equal to 5, the InGaP barrier layer making contact with the first DBR layer is a lower InGaP barrier layer, the InGaP barrier layer making contact with the second DBR layer is an upper InGaP barrier layer, the InGaP barrier layer located between the InGaAs potential well layers is a middle InGaP barrier layer, the thickness of the upper InGaP barrier layer is smaller than or equal to the thickness of the middle InGaP barrier layer, and the thickness of the lower InGaP barrier layer is smaller than or equal to the thickness of the middle InGaP barrier layer. According to the VCSEL device, the reliability of the VCSEL device is improved, and meanwhile, the advantage of high transmission rate is kept.

Description

Technical Field

[0001] The utility model relates to the field of optoelectronic technology, in particular to a vertical cavity surface emitting laser and a laser array. Background Art

[0002] Vertical-cavity surface-emitting laser (VCSEL) is a new generation of semiconductor laser with advantages such as low threshold current, circular spot, low cost, high modulation rate, and easy two-dimensional integration. It plays an important role in short-distance data communication.

[0003] Currently, the wavelength of a typical high-speed VCSEL is generally 850nm to 980nm, and its multiple quantum well (MQW) generally adopts an AlGaAs / InGaAs quantum well structure. However, due to the significant difference in the electrochemical properties of Al and In, defects are easily generated in the AlGaAs barrier and InGaAs potential well, making the device reliability unsatisfactory.

[0004] To achieve more reliable vertical cavity surface emitting lasers (VCSELs), some companies have inserted GaAs, GaP, or GaAsP materials between the AlGaAs barrier and the InGaAs well to reduce defects at the interface between the AlGaAs barrier and the InGaAs well, thereby improving device reliability. However, the insertion of GaAs, GaP, or GaAsP materials into the interface causes a change in the energy band gap, affecting the high-frequency performance of the VCSEL. Utility Model Content

[0005] The technical problem to be solved by the present invention is to provide a vertical cavity surface emitting laser and a laser array, which have a specific InGaAs / InGaP multi-quantum well structure, while improving the reliability of VCSEL devices, maintaining the advantage of high transmission rate.

[0006] In order to solve the above technical problems, the technical solution of the utility model is:

[0007] A vertical cavity surface emitting laser comprises a substrate, a first DBR layer, a quantum well active region, an oxide layer, and a second DBR layer stacked in sequence from bottom to top. The quantum well active region comprises alternately arranged InGaAs well layers and InGaP barrier layers, each InGaAs well layer is inserted between two adjacent InGaP barrier layers, the number of InGaAs well layers is m, and 3≤m≤5. The InGaP barrier layer in contact with the first DBR layer is a lower InGaP barrier layer, the InGaP barrier layer in contact with the second DBR layer is an upper InGaP barrier layer, and the InGaP barrier layer located between the InGaAs well layers is a middle InGaP barrier layer. The thickness of the upper InGaP barrier layer is less than or equal to the thickness of the middle InGaP barrier layer, and the thickness of the lower InGaP barrier layer is less than or equal to the thickness of the middle InGaP barrier layer.

[0008] Furthermore, the InGaAs potential well layer is specifically In x Ga 1-x As material, InGaP barrier layer is specifically In y Ga 1-y For material P, x is less than y.

[0009] Furthermore, the thickness of the InGaP barrier layer is in the range of 2-8 nm, and the thickness of the InGaAs well layer is in the range of 2-8 nm.

[0010] Furthermore, the oxide layer includes a central unoxidized region and an outer oxidized region, the central unoxidized region is made of AlGaAs material, the outer oxidized region is made of Al2O3 material, and the pore size of the central unoxidized region ranges from 4 to 10 μm.

[0011] Furthermore, the thickness of the oxide layer ranges from 15 to 30 nm.

[0012] Furthermore, the distance from the oxide layer to the quantum well active region is 200-300 nm.

[0013] Furthermore, the first DBR layer is an N-type DBR layer, the second DBR layer is a P-type DBR layer, and the material of the first DBR layer and the second DBR layer is AlGaAs.

[0014] Furthermore, a cap layer is included, and the cap layer is located on the second DBR layer.

[0015] Furthermore, the material of the cap layer is a highly doped GaAs material.

[0016] A laser array comprises a plurality of the vertical cavity surface emitting lasers mentioned above.

[0017] The utility model has the following advantages:

[0018] 1. Using compressively strained or tensile strained InGaP materials as MQW barrier materials. MQW adopts a completely Al-free design, which effectively reduces defect density and greatly improves device reliability.

[0019] 2. Using InGaAs potential well layer and InGaP barrier layer (the thickness of the upper InGaP barrier layer, the middle InGaP barrier layer and the lower InGaP barrier layer is limited), the compressive strain potential well can increase the differential gain and enhance the high-frequency performance of the device; the tensile strain barrier can compensate for the stress of the compressive strain potential well, reduce the generation of dislocations, and improve the reliability of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a structural diagram of the utility model;

[0021] Figure 2 It is a schematic diagram of the quantum well active region of the utility model.

[0022] Description of labels

[0023] Substrate 1 First DBR layer 2 Quantum well active region 3 InGaP barrier layer 31

[0024] Lower InGaP barrier layer 311 Middle InGaP barrier layer 312 Upper InGaP barrier layer 313

[0025] InGaAs potential well layer 32 Oxide layer 4 Middle unoxidized region 41 Outer ring oxidized region 42

[0026] second DBR layer 5 , cap layer 6 , first electrode 71 , and second electrode 72 . DETAILED DESCRIPTION

[0027] The present invention will be further described in detail below with reference to the accompanying drawings and examples. It should be noted that the following examples are intended only to illustrate the present invention and are not intended to limit the scope of the present invention. Similarly, the following examples are only partial embodiments of the present invention and are not intended to be exhaustive. All other embodiments derived by persons of ordinary skill in the art without inventive effort are intended to fall within the scope of protection of the present invention.

[0028] In addition, directional terms used in this invention, such as up, down, front, back, left, right, inside, outside, and side, are based on the orientations or positions shown in the accompanying drawings, or are the orientations or positions in which the product is typically placed when in use. These terms are for ease of description only and should not be construed as limitations on this invention. In the various drawings, similarly structured elements are denoted by the same reference numerals. For clarity, the various parts in the drawings are not drawn to scale. Furthermore, some well-known parts may not be shown in the drawings.

[0029] The utility model discloses a vertical cavity surface emitting laser. Figure 1 As shown, a method includes a substrate 1, a first DBR layer 2, a quantum well active region 3, an oxide layer 4, and a second DBR layer 5 stacked in sequence from bottom to top, wherein the quantum well active region 3 includes InGaAs well layers 32 and InGaP barrier layers 31 alternately stacked, each InGaAs well layer 32 is inserted between two adjacent InGaP barrier layers 31, the number of InGaAs well layers 32 is m, 3≤m≤5, the InGaP barrier layer in contact with the first DBR layer 2 is a lower InGaP barrier layer 311, the InGaP barrier layer in contact with the second DBR layer 5 is an upper InGaP barrier layer 313, and the InGaP barrier layer located between the InGaAs well layers 32 is a middle InGaP barrier layer 312, the thickness of the upper InGaP barrier layer 313 is less than or equal to the thickness of the middle InGaP barrier layer 312, and the thickness of the lower InGaP barrier layer 311 is less than or equal to the thickness of the middle InGaP barrier layer 312.

[0030] Furthermore, the InGaAs potential well layer is specifically In x Ga 1-x As material, x is 3%-20%. InGaP barrier layer is specifically In y Ga 1-y P, y is 40%-49%, with x less than y. For example, y = -0.5294x + 0.5059. The larger the x value, the smaller the y value. The thickness of the InGaP barrier layer 31 ranges from 2 to 8 nm, and the thickness of the InGaAs well layer 32 ranges from 2 to 8 nm. The tensile strain barrier compensates for the stress of the compressive strain well, reducing dislocation generation. The use of an InGaAs / InGaP Al-free MQW structure in semiconductor lasers operating in the 800-900 nm band effectively reduces defect density and significantly improves device reliability.

[0031] Furthermore, the oxide layer 4 includes a central unoxidized area 41 and an outer ring oxide area 42, wherein the central unoxidized area 41 is made of AlGaAs material, and the outer ring oxide area 42 is made of Al2O3 material, and the pore size range of the central unoxidized area 41 is 4-10 μm. If the pore size is less than 4 μm, the current density increases, which will affect the reliability of the device. If the pore size is greater than 10 μm, the resonant frequency decreases and the high-frequency performance of the device deteriorates.

[0032] Furthermore, the thickness of the oxide layer 4 is in the range of 15-30 nm. If the thickness of the oxide layer 4 is greater than 30 nm, the stress of the oxide layer 4 will increase, affecting the device performance. If the thickness of the oxide layer 4 is less than 15 nm, the capacitance will increase and the parasitic cutoff frequency will decrease, affecting the high-frequency performance of the device.

[0033] Further, if Figure 1As shown, the distance from the oxide layer 4 to the quantum well active region 3 is h, 200≤h≤330nm, which can achieve better device performance.

[0034] Furthermore, the first DBR layer is an N-type DBR layer, the second DBR layer is a P-type DBR layer, and the material of the first DBR layer and the second DBR layer is AlGaAs.

[0035] Furthermore, a cap layer 6 is included. The cap layer 6 is located on the second DBR layer 5. The material of the cap layer 6 is highly doped GaAs with a doping concentration of 5E19cm -3 , which is beneficial to contact with the electrode and prevents oxidation of the AlGaAs material of the second DBR layer 5.

[0036] Furthermore, it also includes a first electrode 71 and a second electrode 72 . The first electrode 71 is located on the back side of the substrate 1 , and the second electrode 72 is located on the cap layer 6 .

[0037] Example 1

[0038] like Figure 2 As shown, a vertical cavity surface emitting laser includes a first electrode 71, a substrate 1, a first DBR layer 2, a quantum well active region 3, an oxide layer 4, a second DBR layer 5, a cap layer 6, and a second electrode 72 stacked in sequence from bottom to top. The material of the substrate 1 is n-type GaAs, the first electrode 71 is an N electrode, the second electrode 72 is a P electrode, the first DBR layer 2 is N-type AlGaAs, and the second DBR layer 5 is P-type AlGaAs. The quantum well active region 3 includes three InGaAs potential well layers 32, and the InGaP barrier layer 31 is specifically InGaAs. 0.49 Ga 0.51 P, InGaAs potential well layer 32 is specifically In 0.03 Ga 0.97 As, the thickness of the upper InGaP barrier layer 313 is less than the thickness of the middle InGaP barrier layer 312, and the thickness of the lower InGaP barrier layer 311 is less than the thickness of the middle InGaP barrier layer 312. Specifically, the thickness of the upper InGaP barrier layer 313 is in the range of 4 nm, the thickness of the middle InGaP barrier layer 312 is in the range of 6 nm, the thickness of the lower InGaP barrier layer 311 is in the range of 4 nm, and the thickness of the InGaAs well layer 32 is in the range of 6 nm. The obtained vertical cavity surface emitting laser is marked as sample 1.

[0039] Example 2

[0040] The difference from Example 1 is that the thickness of the upper InGaP barrier layer 313 is equal to the thickness of the middle InGaP barrier layer 312, and the thickness of the lower InGaP barrier layer 311 is equal to the thickness of the middle InGaP barrier layer 312. Specifically, the thickness of the upper InGaP barrier layer 313 is in the range of 6 nm, the thickness of the middle InGaP barrier layer 312 is in the range of 6 nm, and the thickness of the lower InGaP barrier layer 311 is in the range of 6 nm. The obtained vertical cavity surface emitting laser is labeled as Sample 2.

[0041] Example 3

[0042] The difference from the first embodiment is that the quantum well active region 3 includes four InGaAs potential well layers 32, and the InGaP barrier layer 31 is specifically InGaAs. 0.4 Ga 0.6 P, InGaAs potential well layer 32 is specifically In 0.2 Ga 0.8 As, the thickness of the upper InGaP barrier layer 313 is less than the thickness of the middle InGaP barrier layer 312, and the thickness of the lower InGaP barrier layer 311 is less than the thickness of the middle InGaP barrier layer 312. Specifically, the thickness of the upper InGaP barrier layer 313 is in the range of 6 nm, the thickness of the middle InGaP barrier layer 312 is in the range of 8 nm, the thickness of the lower InGaP barrier layer 311 is in the range of 6 nm, and the thickness of the InGaAs well layer 32 is in the range of 8 nm. The obtained vertical cavity surface emitting laser is labeled as sample 3.

[0043] Comparative Example

[0044] The difference from the first embodiment is that: Al 0.35 Ga 0.65 As barrier layer, and the obtained vertical cavity surface emitting laser is marked as sample 4.

[0045] The above samples were tested for bandwidth and reliability, and the results are shown in the following table:

[0046] Serial number Bandwidth (GHz) Reliability (h@100℃ / 9mA) Sample 1 18.5 1500 Sample 2 18.8 1450 Sample 3 19.2 1650 Sample 4 18.9 350

[0047] As can be seen from the chart, when using compressively strained or tensilely strained InGaP materials as MQW barrier materials, there is no obvious difference in the bandwidth parameters of samples 1, 2, 3 and 4. The reliability parameters of samples 1, 2 and 3 are much greater than the reliability parameters of sample 4, which greatly improves the device life.

[0048] Compared with the traditional AlGaAs-based material system, the advantages of using an aluminum-free system for semiconductor lasers are: 1. To reduce the defects at the interface between the barrier and the potential well; 2. The tensile strain barrier can compensate for the stress of the compressive strain potential well and reduce the generation of dislocations.

[0049] In 0.49 Ga 0.51 P and Al 0.35 Ga 0.65 The following comparison of As material parameters shows that the two materials are very similar in terms of bandgap width, lattice constant and electron mobility. After replacing AlGaAs material with InGaP as the barrier material in MQW (Multiple Quantum Well), the reliability of VCSEL devices is improved while maintaining the advantage of high transmission rate.

[0050]

[0051]

[0052] The utility model also provides a laser array, comprising a plurality of the above-mentioned vertical cavity surface emitting lasers, which is applied to the fields of laser radar, monitoring fill light, laser heating, etc.

[0053] The above description is only a preferred embodiment of the present invention and does not limit the technical scope of the present invention. Therefore, any changes or modifications made according to the claims and description of the present invention should fall within the scope of the present invention patent.

Claims

1. A vertical cavity surface emitting laser, characterized in that: The invention comprises a substrate, a first DBR layer, a quantum well active region, an oxide layer and a second DBR layer stacked in sequence from bottom to top, wherein the quantum well active region comprises alternately arranged InGaAs potential well layers and InGaP barrier layers, each InGaAs potential well layer is inserted between two adjacent InGaP barrier layers, the number of InGaAs potential well layers is m, 3≤m≤5, the InGaP barrier layer in contact with the first DBR layer is a lower InGaP barrier layer, the InGaP barrier layer in contact with the second DBR layer is an upper InGaP barrier layer, the InGaP barrier layer located between the InGaAs potential well layers is a middle InGaP barrier layer, the thickness of the upper InGaP barrier layer is less than or equal to the thickness of the middle InGaP barrier layer, and the thickness of the lower InGaP barrier layer is less than or equal to the thickness of the middle InGaP barrier layer.

2. The vertical cavity surface emitting laser according to claim 1, wherein: The InGaAs potential well layer is specifically In x Ga 1-x As material, InGaP barrier layer is specifically In y Ga 1-y For material P, x is less than y.

3. The vertical cavity surface emitting laser according to claim 1, wherein: The thickness of the InGaP barrier layer is in the range of 2-8 nm, and the thickness of the InGaAs well layer is in the range of 2-8 nm.

4. The vertical cavity surface emitting laser according to claim 1, wherein: The oxide layer includes a central unoxidized area and an outer oxidized area. The central unoxidized area is made of AlGaAs material, the outer oxidized area is made of Al2O3 material, and the pore size of the central unoxidized area ranges from 4 to 10 μm.

5. The vertical cavity surface emitting laser according to claim 1, wherein: The thickness of the oxide layer ranges from 15-30 nm.

6. The vertical cavity surface emitting laser according to claim 1, characterized in that: The distance from the oxide layer to the quantum well active region is 200-300nm.

7. The vertical cavity surface emitting laser according to claim 1, characterized in that: The first DBR layer is an N-type DBR layer, the second DBR layer is a P-type DBR layer, and the materials of the first DBR layer and the second DBR layer are AlGaAs.

8. The vertical cavity surface emitting laser according to claim 1, wherein: The invention further comprises a cap layer, which is located on the second DBR layer.

9. The vertical cavity surface emitting laser according to claim 8, characterized in that: The material of the cap layer is highly doped GaAs material.

10. A laser array, characterized in that: The method comprises a plurality of vertical cavity surface emitting lasers according to any one of claims 1 to 9.

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