CN115084310A - LED for optical communication and preparation method thereof - Google Patents

Abstract

The present invention provides an LED for optical communication and a preparation method thereof. The LED comprises a conductive substrate, a metal bonding layer, a metal reflection layer, an n-type GaN-1 layer and an i-GaN layer sequentially connected from bottom to top , p-type GaN layer, multiple quantum well layer, n-type GaN-2 layer and insulating layer. Adding p‑i‑n structure GaN-based optoelectronic devices above the p-type GaN layer can provide more holes for the p-type GaN layer while detecting ultraviolet light, improve the carrier injection efficiency, and achieve a more balanced current carrier It is beneficial to the improvement of carrier recombination efficiency and can be used in the field of visible light communication.

Description

A kind of LED for optical communication and preparation method thereof

technical field

The invention belongs to the technical field of semiconductor devices, and in particular relates to an LED used for optical communication and a preparation method thereof.

Background technique

LEDs are considered ideal light sources for visible light communication (VLC) systems because of their excellent optoelectronic properties and the physical properties of semiconductor devices that flicker at high speeds. In order to improve the communication rate and communication quality of the entire communication system, it is very important to increase the modulation bandwidth (-3dB bandwidth) of the LED while maintaining a certain luminous power. However, the modulation bandwidth of current commercial LEDs is usually only a few megahertz to ten megahertz, which is far from meeting the requirements of high-speed visible light communication. In order to achieve more compact and efficient receiver-transmitter modules, the integration of multiple optoelectronic devices on a single chip can improve device performance to overcome fundamental limitations of materials and physical properties, enabling simultaneous detection, communication, and illumination. requirements, while being able to overcome the decrease in recombination efficiency caused by the severe asymmetry of electron and hole concentrations.

SUMMARY OF THE INVENTION

The present invention aims to solve at least one of the technical problems existing in the above-mentioned prior art. To this end, the first aspect of the present invention proposes an LED for optical communication, which can integrate detection, communication and illumination.

A second aspect of the present invention provides a method for manufacturing the LED for optical communication.

According to a first aspect of the present invention, an LED for optical communication is proposed, comprising a conductive substrate, a metal bonding layer, a metal reflective layer, an n-type GaN-1 layer, an i- A GaN layer, a p-type GaN layer, a multiple quantum well layer, an n-type GaN-2 layer and an insulating layer; the LED further includes an N-electrode and a P-electrode, and the N-electrode penetrates from the n-type GaN-1 layer to the n-type GaN -2 layer and form ohmic contact with the n-type GaN-2 layer, the p-electrode is in contact with the p-type GaN layer to form electrical conduction.

In the present invention, the p-i-n structure GaN detector structure is added above the p-type GaN layer, which can realize the detection of ultraviolet light, and provide more holes for the p-type GaN layer after the ultraviolet light is incident, so as to improve the carrier injection. efficiency, to achieve a more balanced carrier concentration, which is beneficial to the improvement of the carrier recombination efficiency.

In some embodiments of the present invention, the conductive substrate is a Si substrate with a thickness of 50 μm˜500 μm.

In some preferred embodiments of the present invention, the metal bonding layer includes at least one alloy selected from Ni, Au, Sn, and Ti; preferably, the metal bonding layer has a thickness of 0.5 μm～ 5.0 μm.

In some more preferred embodiments of the present invention, the metal reflective layer is an Ag or Al metal layer with a thickness of 0.2 μm˜4.0 μm.

In some more preferred embodiments of the present invention, the thicknesses of the n-type GaN-1 layer and the n-type GaN-2 layer are both 0.3 μm˜5 μm.

In some more preferred embodiments of the present invention, the thickness of the i-GaN layer is 10 nm˜100 nm.

In some more preferred embodiments of the present invention, the thickness of the p-type GaN layer is 10 nm˜300 nm.

In some more preferred embodiments of the present invention, the thickness of the multiple quantum well layer is 20 nm to 100 nm.

In some more preferred embodiments of the present invention, the insulating layer is a SiO ₂ insulating layer with a thickness of 100 nm˜2000 nm.

In some more preferred embodiments of the present invention, the electrode includes an alloy of at least one of Ti, Al, Au, and Pt; preferably, the electrode has a thickness of 2 μm˜4 μm.

According to a second aspect of the present invention, a method for preparing the LED for optical communication is proposed, comprising the following steps:

S1: growing a buffer layer, an n-type GaN-2 layer, a multiple quantum well layer, a p-type GaN layer, an i-GaN layer and an n-type GaN-1 layer on an epitaxial substrate;

S2: depositing a metal reflective layer on the n-type GaN-1 layer, setting a groove on the metal reflective layer penetrating the n-type GaN-2 layer, depositing an N electrode and the n-electrode in the groove type GaN-2 layer to form an ohmic contact, then deposit a metal bonding layer and bond the conductive substrate to obtain an epitaxial wafer;

S3: After turning the epitaxial wafer in S2 upside down by 180°, peel off the epitaxial substrate and the buffer layer to expose the n-type GaN-2 layer;

S4: deposit an insulating layer on the n-type GaN-2 layer exposed in S3, and set a stepped structure through to the p-type GaN layer, and deposit a p electrode on the stepped structure, and the p-type The GaN layer forms an ohmic contact.

In some embodiments of the present invention, in S3, any one of mechanical thinning, chemical polishing, and laser lift-off is used to lift off the epitaxial substrate.

In some preferred embodiments of the present invention, in S3, the buffer layer is stripped by ICP dry etching.

In some more preferred embodiments of the present invention, in S4, photolithography lift-off and ICP etching are used to prepare the grooves.

The beneficial effects of the present invention are:

In the present invention, a p-i-n structure GaN-based optoelectronic device is added above the p-type GaN layer, which can provide more holes for the p-type GaN layer while detecting ultraviolet light, improve the carrier injection efficiency, and realize a more balanced carrier concentration. , which is beneficial to the improvement of carrier recombination efficiency and can be used in the field of visible light communication.

Description of drawings

The present invention will be further described below in conjunction with the accompanying drawings and embodiments, wherein:

FIG. 1 is a schematic cross-sectional view of the structure of an LED chip used for visible light communication in Embodiments 1 and 2 of the present invention.

FIG. 2 is a schematic cross-sectional view of the structure of an LED chip of a comparative example of the present invention.

Reference signs: 1. Conductive substrate; 2. Metal bonding layer; 3. Metal reflection layer; 4. n-type GaN-1 layer; 5. i-GaN layer; 6. p-type GaN layer; 7. Multi-quantum Well layer; 8, n-type GaN-2 layer; 9, insulating layer; 10, N electrode; 11, P electrode; 901, first insulating layer; 902, second insulating layer.

Detailed ways

The concept of the present invention and the technical effects produced will be clearly and completely described below with reference to the embodiments, so as to fully understand the purpose, characteristics and effects of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative efforts are all within the scope of The scope of protection of the present invention.

Example 1

In this embodiment, an LED for visible light communication is prepared. The schematic diagram of the structure is shown in FIG. 1 , including a conductive substrate 1 , a metal bonding layer 2 , a metal reflective layer 3 , and n-type GaN, which are sequentially connected from bottom to top. -1 layer 4, i-GaN layer 5, p-type GaN layer 6, multiple quantum well layer 7, n-type GaN-2 layer 8 and insulating layer 9; the LED further includes N electrode 10 and P electrode 11, the The N electrode 10 penetrates from the n-type GaN-1 layer 4 to the n-type GaN-2 layer 8 and forms ohmic contact with the n-type GaN-2 layer 8 , and the P electrode 11 is in electrical conduction with the p-type GaN layer 6 .

The conductive substrate 1 is a Si substrate with a thickness of 400 μm; the metal bonding layer 2 is Ni/Au with a thickness of 600 nm; the metal reflective layer 3 is an Ag metal layer with a thickness of 400 nm; the thickness of the n-type GaN-1 layer 4 The thickness of the i-GaN layer 5 is 10 nm; the thickness of the p-type GaN layer 6 is 200 nm; the InGaN/GaN multiple quantum well layer 7 with a thickness of 50 nm; the n-type GaN-2 layer 8 with a thickness of 2 μm; the insulating layer 9 is 400nm thick _SiO2 insulating layer; the LED also includes N electrode 10 and P electrode 11, the N electrode 10 penetrates from the n-type GaN-1 layer 4 to the n-type GaN-2 layer 8 and is connected with the n-type GaN-2 layer The layer 8 forms an ohmic contact, and the p-electrode 11 is in contact with the p-type GaN layer 6 to form electrical conduction. The metal electrode is a composite electrode composed of Ti/Al/Ti/Au.

The preparation method of the LED for visible light communication is as follows:

S1: Take an epitaxial substrate (Si substrate), and use MOCVD equipment to grow an AlGaN buffer layer, an n-type GaN-2 layer 8, an InGaN/GaN multiple quantum well layer 7, and a p-type GaN layer 6 on the Si substrate in sequence , i-GaN layer 5 and GaN-1 layer 4 to obtain LED epitaxial wafer;

S2: Use electron beam evaporation equipment to deposit a metal reflective layer 3 on the n-type GaN-1 layer 4, and use an etching process to prepare a groove-like structure extending through the n-type GaN-2 layer 8, and deposit metal N in the groove The electrode 10 forms an ohmic contact with the n-type GaN-2 layer 8; the metal bonding layer 2 is then deposited by electron beam evaporation equipment, and is bonded and connected to the conductive substrate 1 through a metal bonding process. Pressure was applied at the center of the substrate 1, and gradually expanded to the edge. After reaching the bonding pressure of 2MPa, the substrate was bonded at a temperature of 300 °C for 2 hours, then annealed, taken out and sent to an annealing furnace, held at 200 °C for 30 minutes, and pre-bonded Form a strong bond between the bonded wafers;

S3: The epitaxial substrate (Si substrate) in the wafer in S2 is mechanically ground and then immersed in a mixture of hydrofluoric acid, glacial acetic acid and nitric acid, etched until the epitaxial substrate disappears, and then ICP etching is used Remove the AlGaN buffer layer to expose the n-type GaN-2 layer 8;

S4: growing an insulating layer 9 on the exposed n-type GaN-2 layer 8;

S5 : using an etching process to prepare a stepped structure penetrating to the p-type GaN layer 6 , and depositing a P electrode 11 on the stepped structure to form a corresponding ohmic contact with the p-type GaN layer 6 .

Example 2

In this example, an LED for visible light communication is prepared. The difference from Example 1 lies in the growth sequence of the epitaxial material on the substrate. The thickness of each layer is the same as that in Example 1. The specific preparation process is as follows:

S1: Take an epitaxial substrate (Si substrate), and use MOCVD equipment to sequentially grow an AlGaN buffer layer, a GaN-1 layer 4, an i-GaN layer 5, a p-type GaN layer 6, and an InGaN/GaN layer on the Si substrate. Quantum well layer 7, n-type GaN-2 layer 8, LED epitaxial wafer is obtained;

S2: use electron beam evaporation equipment to deposit the metal reflective layer 3 on the n-type GaN-2 layer 8, and use an etching process to prepare a groove-like structure that penetrates to the n-type GaN-1 layer 4, and deposit in the groove-like structure The metal N electrode forms an ohmic contact with the n-type GaN-1 layer 4;

S3: On the basis of S2, the metal bonding layer 2 is deposited by electron beam evaporation equipment, and is bonded and connected to the conductive substrate 1 through a metal bonding process. During the bonding process, the application is started from the center of the conductive substrate 1 After reaching the bonding pressure of 2MPa, bond at 300°C for 2h, then anneal, take it out and send it to the annealing furnace, hold at 200°C for 30min, and form a firm bond between the pre-bonded wafers. Bond;

S4: The epitaxial substrate (Si substrate) in the wafer in S3 is mechanically ground and then immersed in a mixture of hydrofluoric acid, glacial acetic acid and nitric acid, etched until the epitaxial substrate disappears, and then ICP etching is used Remove the AlGaN buffer layer to expose the n-type GaN-1 layer 4;

S5: growing the insulating layer 9 on the n-type GaN-1 layer 4 by PECVD;

S6 : using an etching process to prepare a stepped structure penetrating to the p-type GaN layer 6 , and depositing the p-electrode 11 thereon to form a corresponding ohmic contact with the p-type GaN layer 6 .

Comparative ratio

An LED chip was prepared in this comparative example, as shown in FIG. 2 , from bottom to top: conductive substrate 1 , metal bonding layer 2 , first insulating layer 901 , metal reflective layer 4 , p-type GaN layer 6 , a multiple quantum well layer 7, an n-type GaN layer 8 and a second insulating layer 902; the LED also includes an N electrode 10 and a P electrode 11, the N electrode 10 penetrates to the n-type GaN layer 8 to form an ohmic contact, The p-electrode 11 is located above the p-type GaN layer 6 .

S1: Take an epitaxial substrate (Si substrate), and use MOCVD equipment to sequentially grow an AlGaN buffer layer, an n-type GaN layer 8, an InGaN/GaN multiple quantum well layer 7, and a p-type GaN layer 6 on the Si substrate to prepare get LED epitaxial wafer;

S2: use electron beam evaporation equipment to deposit the metal reflective layer 4 on the p-type GaN layer 6, and use an etching process to prepare a groove-like structure extending through the n-type GaN layer 8, and deposit a metal N electrode 10 in the groove-like structure form an ohmic contact;

S3: On the basis of S2, use PECVD and electron beam evaporation equipment to deposit the second insulating layer 902 and the metal bonding layer 2 respectively, and bond them to the conductive substrate 1 through a metal bonding process. The conductive substrate 1 begins to apply pressure at the center and gradually expands to the edge. After reaching the bonding pressure of 2MPa, the conductive substrate 1 is bonded at a temperature of 300 °C for 2 hours, then annealed, taken out, and sent to an annealing furnace. A firm bond is formed between the bonded wafers;

S4: The epitaxial substrate (Si substrate) in the wafer in S3 is mechanically ground and then immersed in a mixture of hydrofluoric acid, glacial acetic acid and nitric acid, etched until the epitaxial substrate disappears, and then ICP etching is used Remove the AlGaN buffer layer to expose the n-type GaN-2 layer 8;

S5: growing the first insulating layer 901 on the n-type GaN-2 layer 8 by PECVD;

S6 : using an etching process to prepare a stepped structure penetrating to the p-type GaN layer 6 , and depositing the p-electrode 11 thereon to form a corresponding ohmic contact with the p-type GaN layer 6 .

The LED chips prepared in Example 1, Example 2 and Comparative Example were irradiated with ultraviolet light while the 100mA current was tested, and the performance test was carried out. The results are shown in Table 1:

Table 1

project Example 1 Example 2 Comparative ratio Bandwidth (MHz) 63 60 35

As shown in Table 1, the modulation bandwidth of the LED chips of Example 1 and Example 2 is higher than that of the LED chips in the comparative example, the main reason is that the carrier injection efficiency can be improved after ultraviolet light irradiation, and the active region can be improved at the same time. radiative recombination efficiency.

The embodiments of the present invention have been described in detail above, but the present invention is not limited to the above-mentioned embodiments, and various changes can be made within the scope of knowledge possessed by those of ordinary skill in the art without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and features in the embodiments may be combined with each other without conflict.

Claims (10)

1. An LED for optical communication, characterized in that: comprising a conductive substrate, a metal bonding layer, a metal reflective layer, an n-type GaN-1 layer, an i-GaN layer, a p-type connected sequentially from bottom to top The GaN layer, the multiple quantum well layer, the n-type GaN-2 layer and the insulating layer; the LED further includes an N electrode and a P electrode, and the N electrode penetrates from the n-type GaN-1 layer to the n-type GaN-2 layer and is connected with the n-type GaN-1 layer. The n-type GaN-2 layer forms an ohmic contact, and the p-electrode is in contact with the p-type GaN layer to form electrical conduction. 2 . The LED for optical communication according to claim 1 , wherein the thicknesses of the n-type GaN-1 layer and the n-type GaN-2 layer are both 0.3 μm to 5 μm. 3 . 3 . The LED for optical communication according to claim 1 , wherein the thickness of the i-GaN layer is 10 nm˜100 nm. 4 . 4 . The LED for optical communication according to claim 1 , wherein the thickness of the p-type GaN layer is 10 nm˜300 nm. 5 . 5 . The LED for optical communication according to claim 1 , wherein the multiple quantum well layer has a thickness of 20 nm to 100 nm. 6 . 6. The LED for optical communication according to claim 1, wherein the metal bonding layer comprises at least one alloy selected from the group consisting of Ni, Au, Sn, and Ti; the metal bonding layer The thickness of 0.5μm ~ 5.0μm. 7 . The LED for optical communication according to claim 1 , wherein the metal reflective layer is an Ag or Al metal layer with a thickness of 0.2 μm˜4.0 μm. 8 . 8 . The LED for optical communication according to claim 1 , wherein the insulating layer is a SiO ₂ insulating layer with a thickness of 100 nm˜2000 nm. 9 . 9. A method for preparing an LED for optical communication according to any one of claims 1 to 8, characterized in that it comprises the following steps: S1: growing a buffer layer, an n-type GaN-2 layer, a multiple quantum well layer, a p-type GaN layer, an i-GaN layer and an n-type GaN-1 layer on an epitaxial substrate; S2: depositing a metal reflective layer on the n-type GaN-1 layer, setting a groove on the metal reflective layer penetrating the n-type GaN-2 layer, depositing an N electrode and the n-electrode in the groove type GaN-2 layer to form an ohmic contact, then deposit a metal bonding layer and bond the conductive substrate to obtain an epitaxial wafer; S3: After turning the epitaxial wafer in S2 upside down by 180°, peel off the epitaxial substrate and the buffer layer to expose the n-type GaN-2 layer; S4: deposit an insulating layer on the n-type GaN-2 layer exposed in S3, and set a stepped structure through to the p-type GaN layer, and deposit a p electrode on the stepped structure, and the p-type The GaN layer forms an ohmic contact. 10 . The preparation method according to claim 9 , wherein in S4 , the grooves are prepared by photolithography stripping and ICP etching. 11 .

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