Vertical cavity surface emitting laser chip

Abstract

The application provides a vertical cavity surface emitting laser chip, which comprises a substrate and, from bottom to top, a buffer layer, an N-type DBR layer, a first SCH layer, a second SCH layer, a quantum well structure layer, a third SCH layer, an oxidation structure layer, a P-type DBR layer and a P-type contact layer, wherein a tunneling layer is prepared between the first SCH layer and the quantum well structure layer, the band gap of the tunneling layer is larger than that of the quantum well structure layer, carriers are transmitted to the tunneling layer through the N-type DBR layer and the first SCH layer, and then are injected into the quantum well structure layer in a tunneling mode to be transmitted in a tunneling mode. The application increases the tunneling layer between the SCH layer and the quantum well structure layer, and optimizes the thickness of the barrier layer in the quantum well structure layer, so that the carriers are injected into the quantum well structure layer in a tunneling mode and are transmitted in a tunneling mode between the quantum well layer and the barrier layer, thereby improving the carrier transmission effect and the hot carrier effect and increasing the differential gain, and finally realizing high modulation bandwidth.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of semiconductor technology, in particular to a high-speed vertical cavity surface emitting laser chip with tunneling injection. BACKGROUND

[0002] The vertical cavity surface emitting laser used in the field of communication has many advantages such as high data transmission rate, low cost, low power consumption, etc. With the rapid growth of communication capacity, there is an urgent need for vertical cavity surface emitting lasers with higher data transmission rate, and the data transmission rate of the vertical cavity surface emitting laser is determined by its modulation bandwidth, the higher the modulation bandwidth, the higher the data transmission rate. The main factors limiting the modulation bandwidth of the vertical cavity surface emitting laser are the carrier transport effect and the hot carrier effect. The important reason for limiting the carrier transport effect and the hot carrier effect is that the band gap of the SCH (Separate Confinement Heterostructure) layer and the barrier layer is relatively high, and the carrier needs to cross the high energy level of the SCH layer and the barrier layer for transmission, which greatly hinders the effective injection of the carrier and the transmission between the quantum wells. Therefore, improving the carrier transport effect of the carrier passing through the SCH layer and the barrier layer will greatly improve the modulation bandwidth of the vertical cavity surface emitting laser. SUMMARY

[0003] In view of the above problems, the purpose of the present application is to provide a vertical cavity surface emitting laser chip, by adding a tunneling layer between the SCH layer and the quantum well layer, and optimizing the thickness of the barrier layer, so that the carrier is injected into the quantum well in a tunneling manner and tunnels between the quantum wells, thereby improving the carrier transport effect and the carrier heat effect, and improving the modulation bandwidth of the vertical cavity surface emitting laser.

[0004] To achieve the above-mentioned purpose, the present application adopts the following specific technical solutions:

[0005] The vertical cavity surface emitting laser chip provided by the present application comprises a substrate and a buffer layer, an N-type DBR layer, a first SCH layer, a second SCH layer, a quantum well structure layer, a third SCH layer, an oxidation structure layer, a P-type DBR layer and a P-type contact layer prepared on the substrate in sequence from bottom to top, and a tunneling layer is prepared between the first SCH layer and the quantum well structure layer. The band gap of the tunneling layer is greater than the band gap of the quantum well structure layer, the carrier is transmitted to the tunneling layer through the N-type DBR layer and the first SCH layer in sequence, then injected into the quantum well structure layer in a tunneling manner through the tunneling layer, and transmitted in the quantum well structure layer in a tunneling manner.

[0006] Preferably, the quantum well structure layer comprises a quantum well layer and a barrier layer stacked in sequence, the band gap of the tunneling layer is greater than the band gap of the barrier layer, and the carrier is transmitted between the quantum well layer and the barrier layer in a tunneling manner.

[0007] Preferably, the number of quantum well layers is three to five.

[0008] Preferably, the first SCH layer comprises a first SCH sub-layer and a second SCH sub-layer, the band gap of the second SCH sub-layer is smaller than the band gap of the first SCH sub-layer, and the band gap of the second SCH layer is the same as the band gap of the first SCH sub-layer.

[0009] Preferably, the oxidation structure layer comprises at least one oxidation layer.

[0010] Compared with the existing vertical cavity surface emitting laser, the present application improves the carrier transport effect and thermal carrier effect and increases the differential gain by adding a tunneling layer between the SCH layer and the quantum well structure layer and optimizing the thickness of the barrier layer in the quantum well structure layer, so as to realize high modulation bandwidth. BRIEF DESCRIPTION OF DRAWINGS

[0011] Figure 1 is a structure schematic diagram of a vertical cavity surface emitting laser chip according to an embodiment of the present application;

[0012] Figure 2 is a schematic diagram of carrier tunneling transport principle of a vertical cavity surface emitting laser chip according to an embodiment of the present application;

[0013] Figure 3 is a schematic diagram of energy band structure and light field distribution inside a vertical cavity surface emitting laser chip according to an embodiment of the present application.

[0014] The reference signs therein include: substrate 1, buffer layer 2, N-type DBR layer 3, first SCH layer 4, first SCH sub-layer 41, second SCH sub-layer 42, quantum well structure layer 5, quantum well layer 51, barrier layer 52, second SCH layer 6, oxidation structure layer 7, P-type DBR layer 8, P-type contact layer 9, tunneling layer 10. DETAILED DESCRIPTION

[0015] Hereinafter, embodiments of the present application will be described with reference to the accompanying drawings. In the following description, the same modules are denoted by the same reference numerals. In the case of the same reference numerals, their names and functions are also the same. Therefore, detailed descriptions thereof will not be repeated.

[0016] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and do not constitute a limitation on the present application.

[0017] Figure 1The structure of the vertical cavity surface emitting laser chip provided by the embodiment of the present application is shown.

[0018] As shown in the figure, Figure 1 The vertical cavity surface emitting laser chip provided by the embodiment of the present application comprises: a substrate 1, a buffer layer 2, an N-type DBR layer 3, a first SCH layer 4, a quantum well structure layer 5, a second SCH layer 6, an oxidation structure layer 7, a P-type DBR layer 8, and a P-type contact layer 9; wherein the substrate 1, the buffer layer 2, and the P-type contact layer 9 are all GaAs materials, the N-type DBR layer 3 and the P-type DBR layer 8 are AlGaAs materials, the tunneling layer 10 is AlAs material, the first SCH layer 4 and the second SCH layer 6 are AlGaAs materials, the quantum well structure layer 5 is InGaAs, AlGaAs, GaAsP material, and the oxidation structure layer 7 is AlGaAs material.

[0019] The buffer layer 2, the N-type DBR layer 3, the first SCH layer 4, the quantum well structure layer 5, the second SCH layer 6, the oxidation structure layer 7, the P-type DBR 8, and the P-type contact layer 9 are sequentially prepared on the substrate 1 from bottom to top, and the innovation of the present application is that the tunneling layer 10 is prepared between the first SCH layer 4 and the quantum well structure layer 5, the band gap of the tunneling layer 10 is greater than the band gap of the quantum well structure layer 5, so as to realize the quantum tunneling effect, and the carriers are injected into the quantum well structure layer 5 in a tunneling manner.

[0020] The quantum well structure layer 5 comprises quantum well layers 51 and barrier layers 52 which are alternately stacked, for example: the quantum well structure layer 5 comprises a first quantum well layer, a first barrier layer, a second quantum well layer, a second barrier layer, and an n-layer quantum well layer from bottom to top.

[0021] The band gap of the tunneling layer 10 is greater than the band gap of the quantum well layer 51 and the barrier layer 52, and the quantum tunneling effect is realized.

[0022] The thickness of the barrier layer 52 is optimized, and when the thickness of the barrier layer 52 reaches a specific value, the quantum tunneling effect is realized, so that the carriers can be transmitted in the quantum well structure layer 5 in a tunneling manner.

[0023] In addition, the thickness of the barrier layer is optimized, so that the coupling effect between the quantum wells can be realized, and the differential gain is improved.

[0024] The band gap of the first SCH layer 4 can be the same as the band gap of the second SCH layer 6, and the second SCH layer 6 plays a role of limiting the leakage of the carriers out of the active region in the laser.

[0025] The band gap of the first SCH layer 4 can be different from the band gap of the second SCH layer 6, in which case the first SCH layer 4 is divided into two sub-layers with different band gaps, i.e. a first SCH sub-layer 41 and a second SCH sub-layer 42, the band gap of the second SCH sub-layer 42 being smaller than the band gap of the first SCH sub-layer 41, and the band gap of the first SCH sub-layer 41 being the same as the band gap of the second SCH layer 6.

[0026] The band gap of the second SCH sub-layer 42 is designed to be smaller than the band gap of the first SCH sub-layer 41, so as to increase the energy level difference between the tunneling layer 10 and the second SCH sub-layer 42, and better realize the quantum tunneling effect and improve the hot carrier effect.

[0027] Of course, the first SCH layer 4 can also adopt other numbers of sub-layers to tunnel the energy level difference between the tunneling layer 10 and the second SCH sub-layer 42. The second SCH layer 6 can also adopt sub-layers with different band gaps to prevent the carriers from leaking out of the active region.

[0028] The oxidation structure layer 7 includes at least one oxidation layer, and preferably six oxidation layers. The more the oxidation layers, the smaller the parasitic capacitance, and the better the photoelectric confinement effect.

[0029] Figure 2 The carrier tunneling transmission principle of the vertical cavity surface emitting laser chip provided by the embodiment of the present application is shown.

[0030] As shown in Figure 2 , the carriers are transmitted in sequence through the N-type DBR layer 3, the first SCH sub-layer 41, the second SCH sub-layer 42, and the tunneling layer 10, and are injected into the first quantum well layer in a tunneling manner, and are transmitted in a tunneling manner between the first quantum well layer, the first barrier layer, the second quantum well layer, the second barrier layer, and the nth quantum well layer.

[0031] Since the tunneling transmission is a relatively fast process, the carriers can be transmitted quickly, and thus the carrier transmission effect can be improved. The tunneling transmission can avoid the relaxation process of the carriers from a higher energy band to a lower energy band (the relaxation process releases a large amount of heat), and thus a large amount of heat is not released, thereby improving the hot carrier effect.

[0032] In addition, the modulation bandwidth is related to the carrier transmission effect, the hot carrier effect, and the differential gain. The faster the carrier transmission rate, the higher the modulation bandwidth, the smaller the thermal effect, and the higher the modulation bandwidth, and the higher the differential gain, and the higher the modulation bandwidth. In the present application, the carriers are transmitted in a tunneling manner, and the tunneling transmission can greatly improve the carrier transmission effect and the hot carrier effect, and the thickness of the barrier layer is optimized, so that the coupling effect occurs between the quantum wells, the differential gain is improved, and the modulation bandwidth is improved through the three improvements.

[0033] Figure 3 The energy band structure and light field distribution inside a vertical cavity surface emitting laser chip are shown according to an embodiment of the present application.

[0034] As shown in Figure 3 The present application adopts a resonant cavity length of λ / 2, 5 quantum wells, and the quantum wells are located at the peak of the light field to obtain maximum gain.

[0035] In the description of the present specification, the description of the terms "one embodiment", "some embodiments", "one example", "another example" or "a specific example" and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any appropriate manner in any one or more embodiments or examples. In addition, the person skilled in the art can combine and combine the different embodiments or examples described in the present specification and the features of the different embodiments or examples without contradiction.

[0036] Although the embodiments of the present application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present application, and those skilled in the art can make changes, modifications, replacements and variations to the above embodiments within the scope of the present application.

[0037] The specific embodiments of the present application described above do not constitute a limitation on the scope of protection of the present application. Any various other corresponding changes and modifications made according to the technical concept of the present application shall be included in the scope of protection of the claims of the present application.

Claims

1. A vertical cavity surface emitting laser chip, comprising a substrate and, successively prepared on the substrate from bottom to top, a buffer layer, an N-type DBR layer, a first SCH layer, a quantum well structure layer, a second SCH layer, an oxidation structure layer, a P-type DBR layer, and a P-type contact layer, characterized in that, A tunnel layer is prepared between the first SCH layer and the quantum well structure layer, the tunnel layer has a band gap greater than that of the quantum well structure layer, carriers are transmitted to the tunnel layer through the N-type DBR layer and the first SCH layer in turn, and then injected into the quantum well structure layer in a tunneling manner and transmitted in the quantum well structure layer in a tunneling manner; the quantum well structure layer comprises quantum well layers and barrier layers which are alternately and sequentially stacked, the tunnel layer has a band gap greater than that of the barrier layers, and by optimizing the thickness of the barrier layers, the quantum tunneling effect is realized when the thickness of the barrier layers reaches a certain value, so that carriers are transmitted between the quantum well layers and the barrier layers in a tunneling manner.

2. The vertical cavity surface emitting laser chip of claim 1, wherein, The number of the quantum well layers is three to five.

3. The vertical cavity surface emitting laser chip according to claim 1 or 2, characterized in that The first SCH layer comprises a first SCH sub-layer and a second SCH sub-layer, the second SCH sub-layer has a band gap smaller than that of the first SCH sub-layer, and the second SCH layer has a band gap identical to that of the first SCH sub-layer.

4. The vertical cavity surface emitting laser chip of claim 1 or 2, wherein The oxidation structure layer comprises at least one oxidation layer.

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