CN106972083A - Preparation method of epitaxial wafer of light-emitting diode - Google Patents

Abstract

The invention discloses a method for preparing an epitaxial wafer of a light-emitting diode, and belongs to the field of optoelectronic technology. The preparation method comprises providing a substrate, and sequentially growing a buffer layer, a nucleation layer, an undoped GaN layer, an N-type layer and an active layer on the substrate, wherein the active layer is grown in the following manner: step 1: stop introducing trimethylgallium into the reaction chamber, and introduce trimethylindium into the reaction chamber to grow an InGaN quantum well layer; step 2: stop introducing trimethylindium into the reaction chamber, and introduce trimethylgallium into the reaction chamber to grow a GaN quantum barrier layer; by using the remaining trimethylgallium when growing the N-type layer or the quantum barrier layer in the reaction chamber to grow the quantum well layer, since only trimethylindium is supplemented when growing the quantum well layer, the In component in the quantum well layer can be increased, thereby increasing the proportion of electrons and holes in the active layer, and improving the luminous efficiency of the light-emitting diode.

Description

A kind of preparation method of epitaxial wafer of light-emitting diode

technical field

The invention relates to the technical field of optoelectronics, in particular to a method for preparing an epitaxial wafer of a light emitting diode.

Background technique

Light Emitting Diode (English: Light Emitting Diode, referred to as: LED), as a very influential new product in the optoelectronics industry, has the characteristics of small size, long service life, colorful colors, and low energy consumption. It is widely used in lighting, display screens , signal lights, backlight, toys and other fields.

The light-emitting area of the epitaxial wafer is mainly the active layer. When electrons and holes recombine in the active layer, light will be radiated, but recombination outside the active layer will not radiate light. The proportion of holes recombined in the active layer is used to improve the luminous efficiency of the light-emitting diode.

The currently known method of increasing the recombination ratio of electrons and holes in the active layer is mainly by providing an electron blocking layer, but only by providing an electron blocking layer is not enough to make the luminous efficiency of the light emitting diode meet the needs of various occasions.

Contents of the invention

In order to solve the problem of low luminous efficiency of existing light-emitting diodes, an embodiment of the present invention provides a method for manufacturing an epitaxial wafer of a light-emitting diode. Described technical scheme is as follows:

An embodiment of the present invention provides a method for preparing an epitaxial wafer of a light-emitting diode, the preparation method comprising:

providing a substrate;

growing a buffer layer, a nucleation layer, and an undoped GaN layer sequentially on the substrate;

Introduce trimethylgallium into the reaction chamber to grow an N-type layer;

An active layer is grown on the N-type layer, wherein the active layer is grown in the following manner:

Step 1: stop feeding trimethylgallium into the reaction chamber, and feed trimethylindium into the reaction chamber to grow an InGaN quantum well layer;

Step 2: stop feeding trimethylindium into the reaction chamber, and feed trimethylgallium into the reaction chamber to grow a GaN quantum barrier layer;

Repeating the above steps 1 and 2 to form the active layer on the N-type layer;

A P-type layer is grown on the active layer.

Preferably, the stopping of introducing trimethylindium into the reaction chamber, and introducing trimethylgallium into the reaction chamber to grow the GaN quantum barrier layer includes:

Stop feeding trimethylindium into the reaction chamber, feed trimethylgallium and N2 into the reaction chamber, and grow a GaN capping layer on the InGaN quantum well layer;

Continue to feed trimethylgallium, N2, and H2 into the reaction chamber to grow a GaN quantum barrier sublayer on the GaN capping layer.

Preferably, the growth temperature of the GaN cap layer is lower than the growth temperature of the GaN quantum barrier sublayer grown thereon.

Further, when the GaN quantum barrier sublayer is grown on the GaN capping layer, the ratio of the amount of H2 and N2 flowing into the reaction chamber is 1:20˜20:1.

Preferably, the number of times of repeating the step 1 and the step 2 is 8-20 times.

Preferably, the growth temperature of the InGaN quantum well layer is 620-750°C.

Preferably, the growth temperature of the GaN quantum barrier layer is 700-900°C.

Further, when growing the GaN quantum barrier layer for the first n times, the preparation method further includes:

Silane is introduced into the reaction chamber, wherein n is less than the total number of GaN quantum barrier layers.

Preferably, the growth thickness of the InGaN quantum well layer is 0.5-5 nm.

Optionally, the growth thickness of the GaN quantum barrier layer is 8-15 nm.

The beneficial effect brought by the technical solution provided by the embodiments of the present invention is: by sequentially growing a buffer layer, a nucleation layer, an undoped GaN layer, an N-type layer, and an active layer on a substrate, wherein the growth of the active layer , by stopping feeding trimethylgallium into the reaction chamber and feeding trimethylindium into the reaction chamber, the remaining trimethylgallium to grow the quantum well layer when growing the N-type layer or the quantum barrier layer in the reaction chamber , since only trimethylindium is supplemented when growing the quantum well layer, the composition of In in the grown quantum well layer can be increased, and the higher the composition of In in the quantum well layer, the quantum well layer has a greater impact on the current carrying capacity. The stronger the confinement effect of electrons, the ratio of electrons and holes recombining in the active layer can be increased, and the luminous efficiency of the light-emitting diode can be improved. Consumption is conducive to reducing production costs.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings that need to be used in the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those skilled in the art, other drawings can also be obtained based on these drawings without creative effort.

1 is a flowchart of a method for preparing an epitaxial wafer of a light-emitting diode provided by an embodiment of the present invention;

2 is a flow chart of another method for preparing an epitaxial wafer of a light-emitting diode provided by an embodiment of the present invention;

3 is a schematic diagram of a conventional growth process of an active layer;

FIG. 4 is a schematic diagram of a growth process of an active layer provided by an embodiment of the present invention.

detailed description

In order to make the object, technical solution and advantages of the present invention clearer, the implementation manner of the present invention will be further described in detail below in conjunction with the accompanying drawings.

Fig. 1 is a flow chart of a method for preparing an epitaxial wafer of a light-emitting diode provided by an embodiment of the present invention. As shown in Fig. 1 , the preparation method includes:

S11: Provide a substrate.

S12: growing a buffer layer, a nucleation layer, and an undoped GaN layer sequentially on the substrate.

S13: passing trimethylgallium into the reaction chamber to grow an N-type layer.

S14: growing an active layer on the N-type layer.

Specifically, step S14 includes:

Step 1: stop feeding trimethyl gallium into the reaction chamber, and feed trimethyl indium into the reaction chamber to grow an InGaN quantum well layer.

Step 2: stop feeding trimethylindium into the reaction chamber, and feed trimethylgallium into the reaction chamber to grow a GaN quantum barrier layer.

Repeat step 1 and step 2 above to form an active layer on the N-type layer.

S15: growing a P-type layer on the active layer.

By sequentially growing a buffer layer, a nucleation layer, an undoped GaN layer, an N-type layer and an active layer on the substrate, wherein, when growing the active layer, by stopping feeding trimethylgallium into the reaction chamber, And feed trimethylindium into the reaction chamber, and use the remaining trimethylgallium to grow the quantum well layer when growing the N-type layer or quantum barrier layer in the reaction chamber, because only trimethylindium is supplemented when growing the quantum well layer , so the composition of In in the grown quantum well layer can be increased, and the higher the composition of In in the quantum well layer, the stronger the confinement effect of the quantum well layer on carriers, which can improve the electron and hole in the The ratio of recombination in the active layer improves the luminous efficiency of the light-emitting diode, and at the same time, because the remaining trimethylgallium in the reaction chamber is used, the consumption of trimethylgallium can be reduced, which is conducive to reducing the production cost.

Fig. 2 is a flowchart of another method for preparing an epitaxial wafer of a light-emitting diode provided by an embodiment of the present invention. As shown in Fig. 2, the preparation method includes:

S21: Provide a substrate.

When implemented, the substrate may be a sapphire substrate. The sapphire substrate is a very common substrate with a mature preparation process, which is conducive to reducing production costs.

In step S21, the sapphire substrate may be pretreated. Specifically, the sapphire substrate may be heated to 1060° C. first, and then the sapphire substrate may be annealed and nitrided for 10 minutes in a hydrogen atmosphere.

S22: growing an AlN buffer layer on the substrate.

Optionally, the growth temperature of the buffer layer is controlled to be 600°C.

During implementation, the sapphire substrate may be placed in a PVD (Physical Vapor Deposition, physical vapor deposition) reaction chamber, and the temperature of the reaction chamber is set at 600°C.

Optionally, a buffer layer with a thickness of 25nm is grown on the sapphire substrate. Since the buffer layer is not doped, too thick a grown buffer layer will increase the forward resistance of the epitaxial wafer, which will increase the forward voltage and shorten the epitaxy. life of the tablet.

Preferably, step S22 may also include:

Anneal the buffer layer.

Specifically, the temperature of the PVD reaction chamber is increased to 1060° C. for annealing, and the annealing time may be 5 minutes.

S23: growing a nucleation layer on the AlN buffer layer.

Optionally, the growth temperature of the nucleation layer may be 1020°C.

Specifically, the sapphire substrate grown with the buffer layer was placed in a MOCVD (Meta1 Organic Chemical Vapor Deposition, metal organic compound chemical vapor deposition) reaction chamber, heated to 1020° C., and the nucleation layer was grown in a pure hydrogen atmosphere.

Optionally, the growth pressure of the nucleation layer may be 390-410 torr.

Optionally, the growth thickness of the nucleation layer may be 780-820 nm.

S24: growing an undoped GaN layer on the nucleation layer.

Optionally, the growth temperature of the undoped GaN layer may be 1100°C.

Optionally, the growth pressure of the undoped GaN layer may be 590-610 torr.

Optionally, the growth thickness of the undoped GaN layer may be 1 μm.

S25: growing an N-type layer on the undoped GaN layer.

Optionally, the growth rate of the N-type layer may be 3.4 μm/h, and its growth thickness may be 2.5 μm.

When realizing, the pressure of the reaction chamber is adjusted to 100torr, TMGa (Trimethylgallium, trimethylgallium) is continuously fed into the reaction chamber, and the N-type layer is grown under a nitrogen-hydrogen mixed atmosphere.

Optionally, the mass ratio of hydrogen and nitrogen is 31:10-40:1.

S26: growing an active layer on the N-type layer.

Specifically, the growth of the active layer includes the growth of multi-layer InGaN quantum well layers and the growth of multi-layer GaN quantum barrier layers.

Fig. 3 is a schematic diagram of a growth process of an existing active layer, and Fig. 4 is a schematic diagram of a growth process of an active layer provided by an embodiment of the present invention. In the figure, interval A represents the growth of an N-type layer, and interval B represents InGaN The growth of the quantum well layer, the C interval indicates the growth of the GaN quantum barrier layer, Δt indicates the process of heating or cooling, ON indicates that the corresponding substance (TMGa or TMIn) is introduced into the reaction chamber, and OFF indicates that the corresponding material (TMGa or TMIn) is stopped into the reaction chamber. Substance (TMGa or TMIn). Here, the growth process of the active layer is specifically described in conjunction with FIG. 4. It should be noted that FIG. 4 only shows the growth of 3 layers of InGaN quantum well layers and GaN quantum barrier layers, and does not mean that the active layer must only include 3 layers. layer InGaN quantum well layer and GaN quantum barrier layer.

When implemented, the growth of InGaN quantum well layers can include:

Step 1: stop feeding TMGa into the reaction chamber, and continuously feed TMIn (Trimethylindium, trimethyl indium) into the reaction chamber to grow an InGaN quantum well layer.

Optionally, the growth temperature of the InGaN quantum well layer may be 620-750°C.

Optionally, the growth pressure of the InGaN quantum well layer may be 300 torr.

Preferably, the growth thickness of the InGaN quantum well layer can be 0.5-5nm. If the thickness of the quantum well layer is too thin, the confinement effect on carriers will be reduced. If the quantum well layer is too thick, it will be caused by the polarization effect. Luminous efficiency decreases.

As shown in Figure 4, after the growth of the N-type layer (or a layer of GaN quantum barrier layer) is completed, the introduction of TMGa into the reaction chamber is stopped, and the temperature of the reaction chamber is lowered to 710°C, and the temperature of the reaction chamber is stabilized to 710°C. °C, start to feed TMIn continuously, and grow the InGaN quantum well layer under nitrogen atmosphere.

Growth of GaN quantum barrier layers can include:

Step 2: stop feeding TMIn into the reaction chamber, and feed TMGa into the reaction chamber to grow a GaN quantum barrier layer.

Optionally, the growth temperature of the GaN quantum barrier layer may be 700-900°C.

Optionally, the growth pressure of the GaN quantum barrier layer may also be 300 torr, or may be greater than or less than 300 torr.

Preferably, the growth thickness of the GaN quantum barrier layer may be 8-15 nm. If the thickness of the quantum barrier layer is too thin or too thick, carrier leakage will occur, resulting in reduced luminous efficiency.

As shown in Figure 4, after the growth of a layer of InGaN quantum well layer is completed, stop feeding TMIn into the reaction chamber, start feeding TMGa continuously, increase the temperature of the reaction chamber to 850°C, and wait for the temperature of the reaction chamber to stabilize to 850°C Afterwards, the GaN quantum barrier layer is grown in a nitrogen-hydrogen mixed atmosphere.

Further, the growth of the GaN quantum barrier layer may include the growth of the GaN capping layer and the growth of the GaN quantum barrier sub-layer.

When it is realized, it is possible to stop feeding trimethylindium into the reaction chamber, feed trimethylgallium and N2 into the reaction chamber, and grow a layer of GaN capping layer on the InGaN quantum well layer; Methylgallium, N2, and H2 are passed through at the same time, and then a layer of GaN quantum barrier sublayer is grown on the GaN capping layer.

Optionally, when growing the GaN quantum barrier sub-layer on the GaN capping layer, the ratio of the amount of H2 and N2 flowing into the reaction chamber is 1:20˜20:1.

When implemented, the growth temperature of the GaN cap layer is lower than the growth temperature of the GaN quantum barrier sublayer grown thereon.

Specifically, after the growth of a layer of InGaN quantum well layer is completed, the introduction of TMIn into the reaction chamber can be stopped, and the introduction of TMGa can be started continuously, and the GaN capping layer can be grown under a hydrogen atmosphere. After the growth of the GaN capping layer is completed, the The temperature of the reaction chamber is up to 850° C., and after the temperature of the reaction chamber is stabilized to 850° C., the growth of the GaN quantum barrier sublayer is carried out in a nitrogen-hydrogen mixed atmosphere.

It should be noted that the growth process of the GaN capping layer is not shown in FIG. 4 .

The active layer is formed on the N-type layer by repeating the growth process of the quantum well layer and the quantum barrier layer.

Optionally, the number of times of repeating step 1 and step 2 is 8-20 times, so that 8-20 layers of quantum well layers and quantum barrier layers can be formed.

Optionally, when growing the GaN quantum barrier layer for the first n times, the preparation method further includes:

Silane is introduced into the reaction chamber, wherein n is less than the total number of GaN quantum barrier layers. For example, there are 10 GaN quantum barrier layers in total, the first 4 layers of GaN quantum barrier layers can be doped, and the last 6 layers are not doped. Proper doping of Si in the GaN quantum barrier layer can effectively reduce the working voltage of the LED.

S27: growing an electron blocking layer on the active layer.

The recombination of electrons and holes outside the active layer can be reduced by growing the electron blocking layer, thereby further improving the luminous efficiency of the light emitting diode.

Optionally, the growth temperature of the electron blocking layer may be 900°C.

Optionally, the growth thickness of the electron blocking layer may be 70 nm, and the growth rate may be 0.3 μm/h.

When it is realized, the reaction chamber is heated to 900° C., and the electron blocking layer is grown under a nitrogen atmosphere.

S28: growing a P-type layer on the electron blocking layer.

Optionally, the growth temperature of the P-type layer may be 950°C.

Optionally, the growth thickness of the P-type layer may be 50 nm.

To implement, the reaction chamber is heated to 950° C., the growth pressure is adjusted to 200 torr, TMGa is introduced into the reaction chamber, and the P-type layer is grown in a nitrogen-hydrogen mixed atmosphere.

An epitaxial wafer with an active layer comprising 10 layers of InGaN quantum well layers and 10 layers of GaN quantum barrier layers produced by the preparation method of the embodiment of the present invention is divided into 4 × 5mil after cleaning, coating, photolithography and other semiconductor processes. The LED chip is tested, its forward voltage can reach 2.95V, the current is 5mA, the output power of a single LED chip is 5.5mW, and the epitaxial wafer grown by the existing technology, the single LED chip obtained through the same chip manufacturing process The output power is only 4.5mW, which is a 22.2% increase in output power.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection of the present invention. within range.

Claims (10)

1. a preparation method of an epitaxial wafer of a light-emitting diode, characterized in that, the preparation method comprises: providing a substrate; growing a buffer layer, a nucleation layer, and an undoped GaN layer sequentially on the substrate; Introduce trimethylgallium into the reaction chamber to grow an N-type layer; An active layer is grown on the N-type layer, wherein the active layer is grown in the following manner: Step 1: stop feeding trimethylgallium into the reaction chamber, and feed trimethylindium into the reaction chamber to grow an InGaN quantum well layer; Step 2: stop feeding trimethylindium into the reaction chamber, and feed trimethylgallium into the reaction chamber to grow a GaN quantum barrier layer; Repeating the above steps 1 and 2 to form the active layer on the N-type layer; A P-type layer is grown on the active layer. 2. The preparation method according to claim 1, wherein the stop feeding trimethylindium into the reaction chamber, and feeding trimethylgallium into the reaction chamber to grow the GaN quantum barrier layers, including: Stop feeding trimethylindium into the reaction chamber, feed trimethylgallium and N2 into the reaction chamber, and grow a GaN capping layer on the InGaN quantum well layer; Continue to feed trimethylgallium, N2, and H2 into the reaction chamber to grow a GaN quantum barrier sublayer on the GaN capping layer. 3 . The preparation method according to claim 2 , wherein the growth temperature of the GaN cap layer is lower than the growth temperature of the GaN quantum barrier sublayer grown thereon. 4 . 4. preparation method according to claim 2, is characterized in that, when growing described GaN quantum barrier sublayer on described GaN cover layer, pass into the H of reaction chamber and N The ratio of the amount of substance is 1: 20～20:1. 5. The preparation method according to any one of claims 1-4, characterized in that the number of times of repeating the step 1 and the step 2 is 8-20 times. 6. The preparation method according to any one of claims 1-4, characterized in that, the growth temperature of the InGaN quantum well layer is 620-750°C. 7. The preparation method according to any one of claims 1-4, characterized in that the growth temperature of the GaN quantum barrier layer is 700-900°C. 8. The preparation method according to any one of claims 1 to 4, characterized in that, when growing the GaN quantum barrier layer for the first n times, the preparation method further comprises: Silane is introduced into the reaction chamber, wherein n is less than the total number of GaN quantum barrier layers. 9. The preparation method according to any one of claims 1-4, characterized in that, the growth thickness of the InGaN quantum well layer is 0.5-5 nm. 10. The preparation method according to any one of claims 1-4, characterized in that the growth thickness of the GaN quantum barrier layer is 8-15 nm.