A red-yellow GaAs LED chip and preparation method thereof

Abstract

The present invention provides a red-yellow GaAs LED chip and a preparation method thereof, wherein the red-yellow GaAs LED chip comprises a GaAs substrate, an epitaxial layer, a highly doped GaP layer and a reflective layer which are stacked in sequence, wherein the highly doped GaP layer comprises a first carbon-doped GaP layer, a second carbon-doped GaP layer, a third carbon-doped GaP layer and a fourth carbon-doped GaP layer which are sequentially arranged, wherein the first carbon-doped GaP layer is arranged on a side close to the epitaxial layer, and a plurality of transition GaP layers are arranged between the first carbon-doped GaP layer and the second carbon-doped GaP layer, and between the second carbon-doped GaP layer and the third carbon-doped GaP layer, wherein the reflective layer comprises a dielectric layer and a metal mirror layer, and the dielectric layer is arranged on a side close to the highly doped GaP layer. The present invention solves the problem of low luminous efficiency of LED chips in the prior art.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a red-yellow GaAs series LED chip and a preparation method thereof. Background Art

[0002] LED mirror preparation is an extremely important process in the production of red-yellow GaAs LED upright reverse polarity vertical structure products. Its main purpose is to improve the brightness of the chip through the prepared mirror.

[0003] When the red-yellow GaAs LED chip MQW (quantum well) emits light, it is mainly used for forward light. Since GaAs material has a high light absorption characteristic, the light emitted from the bottom will be absorbed by GaAs and cannot be reflected back to the front. Therefore, the light emitted by the GaAs chip without a mirror layer is mainly forward light. In order to improve the light emission efficiency and reduce light absorption, the red-yellow GaAs product has a unique forward-mounted reverse polarity product. Its main feature is that a set of mirrors are bonded under the epitaxy, so that when the MQW (quantum well) emits light, the light from the bottom can be reflected back to the forward direction by the mirror, thereby achieving the effect of increasing brightness.

[0004] In the prior art, the mirror structure commonly used in red-yellow GaAs LEDs is mainly Au or Ag as the mirror metal, SiO 2 As a dielectric layer, the epitaxy is used to reflect brightness. Specifically, the LED chip epitaxy is annealed to achieve a fusion effect between the epitaxy and the mirror metal, thereby forming an ohmic contact. However, after annealing, the mirror metal is easily fused and exchanged with the epitaxial layer, resulting in a decrease in the light output efficiency of the LED chip. Summary of the invention

[0005] In view of this, an object of the present invention is to provide a red-yellow GaAs LED chip and a preparation method thereof, aiming to solve the problem of low luminous efficiency of LED chips in the prior art.

[0006] The embodiment of the present invention is implemented as follows: a red-yellow GaAs LED chip comprises a GaAs substrate, an epitaxial layer, a highly doped GaP layer and a reflective layer stacked in sequence, wherein the highly doped GaP layer comprises a first carbon-doped GaP layer, a second carbon-doped GaP layer, a third carbon-doped GaP layer and a fourth carbon-doped GaP layer which are sequentially arranged, wherein the first carbon-doped GaP layer is arranged on a side close to the epitaxial layer, and a plurality of transition GaP layers are arranged between the first carbon-doped GaP layer and the second carbon-doped GaP layer, and between the second carbon-doped GaP layer and the third carbon-doped GaP layer, wherein the reflective layer comprises a dielectric layer and a metal mirror layer, and wherein the dielectric layer is arranged on a side close to the highly doped GaP layer.

[0007] Furthermore, in the above-mentioned red-yellow GaAs LED chip, the carbon doping concentration of the first carbon-doped GaP layer is 3e16cm-3 The doping concentration of the second carbon-doped GaP layer is 3e17cm -3 The doping concentration of the third carbon-doped GaP layer is 5e18cm -3 The doping concentration of the fourth carbon-doped GaP layer is 5e20cm -3 .

[0008] Furthermore, in the above-mentioned red-yellow GaAs LED chip, the growth thickness of the first carbon-doped GaP layer is 5000A, the growth thickness of the second carbon-doped GaP layer is 3000A, the growth thickness of the third carbon-doped GaP layer is 3000A, and the growth thickness of the fourth carbon-doped GaP layer is 100A-300A.

[0009] Furthermore, in the above-mentioned red-yellow GaAs LED chip, the carbon doping concentration of the multiple transition GaP layers gradually increases from the side of the highly doped GaP layer with low carbon doping concentration to the side of the highly doped GaP layer with high carbon doping concentration.

[0010] Furthermore, in the above-mentioned red-yellow GaAs LED chip, the plurality of transition GaP layers are 3e1cm -3 A step gradually transitions from a side of the highly-doped GaP layer with a low carbon doping concentration to a side of the highly-doped GaP layer with a high carbon doping concentration.

[0011] Furthermore, in the above-mentioned red-yellow GaAs LED chip, the growth thickness of the plurality of transition GaP layers is 1000A in total.

[0012] Furthermore, in the above-mentioned red-yellow GaAs LED chip, a first SiO 2 A CB hole is etched on the first SiO2 layer, and then a second SiO 2 layer to form the dielectric layer.

[0013] Furthermore, in the above-mentioned red-yellow GaAs LED chip, a mirror metal is evaporated on a surface of the dielectric layer at a side away from the highly-doped GaP layer to form the mirror metal layer.

[0014] Another object of the present invention is to provide a method for preparing a red-yellow GaAs LED chip, which is used to prepare the above-mentioned red-yellow GaAs LED chip, and the method comprises:

[0015] Providing a GaAs substrate;

[0016] growing an epitaxial layer on the GaAs substrate;

[0017] On the epitaxial layer, sequentially grow a first carbon-doped GaP layer, then grow a transition GaP layer, then continue to grow a second carbon-doped GaP layer, then grow a transition GaP layer, then continue to grow a third carbon-doped GaP layer, and finally grow a fourth carbon-doped GaP layer;

[0018] A first SiO2 layer is grown on the fourth carbon-doped GaP layer as a CB layer, a CB pattern is photolithographically formed on the CB layer, and then a CB hole is wet-etched, and then a second SiO2 layer is grown on the first CB layer.

[0019] Furthermore, in the above-mentioned method for preparing a red-yellow GaAs LED chip, the steps of sequentially growing a first carbon-doped GaP layer on the epitaxial layer, then growing a transition GaP layer, then continuing to grow a second carbon-doped GaP layer, then growing a transition GaP layer, then continuing to grow a third carbon-doped GaP layer, and finally growing a fourth carbon-doped GaP layer include:

[0020] The epitaxial layer is sequentially grown with a doping concentration of 3e16cm -3 The first carbon-doped GaP layer is then grown every 3e1cm -3 A step transition to 3e17cm -3 The transition GaP layer is then grown with a doping concentration of 3e17cm -3 The second carbon-doped GaP layer is then grown every 3e1cm -3 A step transition to 5e18cm -3 The transition GaP layer is then grown with a doping concentration of 5e18cm -3 The third carbon-doped GaP layer is grown with a final doping concentration of 5e20cm -3 A fourth carbon-doped GaP layer.

[0021] Compared with the prior art, the present invention is provided with a highly doped GaP layer on the P-type layer. In the case of no annealing process, although the mirror metal layer and the GaP layer should be in Schottky contact, the present invention utilizes the tunnel effect, and through the extremely thin GaP layer with a high doping concentration, the potential barrier between the semiconductor and the metal is extremely thin, and the relative carrier concentration is extremely high. When excited, the carriers can directly pass through the potential barrier instead of crossing the potential barrier, so that the chip can achieve ohmic contact without annealing, thereby avoiding the problem of reduced light output efficiency of the LED chip caused by fusion exchange between the mirror metal and the epitaxial layer after annealing, and improving the luminous efficiency of the LED chip.

[0022] In addition, the red-yellow GaAs LED chip proposed in the present invention can at least have the following beneficial effects:

[0023] 1. There is no need to select a metal with a lower annealing temperature as the material of the mirror metal layer in order to consider the influence of temperature on the composite efficiency of doping and mirror metal, thereby improving the extensiveness of metal material selection in the mirror metal layer.

[0024] 2. Avoid the overall impact of the annealing process of the mirror metal layer on the chip process. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic structural diagram of a red-yellow GaAs LED chip in the first embodiment of the present invention;

[0026] Figure 2 FIG. 4 is a flow chart of a method for preparing a red-yellow GaAs LED chip according to a second embodiment of the present invention. DETAILED DESCRIPTION

[0027] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0028] In addition, the term "and / or" as used herein includes any and all combinations of one or more related listed items. In the detailed description and claims, a list of items connected by the term "one of" may mean any of the listed items. For example, if items A and B are listed, the phrase "one of A and B" means only A or only B. In another example, if items A, B, and C are listed, the phrase "one of A, B, and C" means only A; only B; or only C. Item A may contain a single element or multiple elements. Item B may contain a single element or multiple elements. Item C may contain a single element or multiple elements. In the detailed description and claims, a list of items connected by the terms "at least one of", "at least one of" or other similar terms may mean any combination of the listed items. For example, if items A and B are listed, the phrase "at least one of A and B" or "at least one of A or B" means only A; only B; or A and B. In another example, if items A, B, and C are listed, the phrase "at least one of A, B, and C" or "at least one of A, B, or C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A may include a single element or multiple elements. Item B may include a single element or multiple elements. Item C may include a single element or multiple elements.

[0029] Example 1

[0030] See also Figure 1, is a red-yellow GaAs LED chip provided in the first embodiment of the present invention, the red-yellow GaAs LED chip comprises a GaAs substrate 1, an epitaxial layer 2, a highly doped GaP layer 3 and a reflective layer 4 which are stacked in sequence, wherein:

[0031] The epitaxial layer 2 includes an N layer 21 , a quantum well layer 22 and a P layer 23 which are grown in sequence.

[0032] The highly doped GaP layer 3 includes a first carbon-doped GaP layer 31, a second carbon-doped GaP layer 32, a third carbon-doped GaP layer 33 and a fourth carbon-doped GaP layer 34 which are arranged in sequence. The first carbon-doped GaP layer 31 is arranged on the side close to the epitaxial layer 2, and multiple transition GaP layers (not shown) are arranged between the first carbon-doped GaP layer 31 and the second carbon-doped GaP layer 32, and between the second carbon-doped GaP layer 32 and the third carbon-doped GaP layer 33.

[0033] By way of example and not limitation, in this embodiment, the carbon doping concentration of the first carbon-doped GaP layer 31 is 3e16 cm -3 The doping concentration of the second carbon-doped GaP layer 32 is 3e17cm -3 The doping concentration of the third carbon-doped GaP layer 33 is 5e18 cm -3 The doping concentration of the fourth carbon-doped GaP layer 34 is 5e20cm -3 .

[0034] Specifically, the first carbon-doped GaP layer 31 has a growth thickness of 5000 Å, the second carbon-doped GaP layer 32 and the third carbon-doped GaP layer 33 have the same growth thickness of 3000 Å, and the fourth carbon-doped GaP layer 34 has a growth thickness of 100 Å-300 Å.

[0035] Furthermore, the carbon doping concentration of the multiple transition GaP layers gradually increases from the side of the high-doped GaP layer 3 with a low carbon doping concentration to the side of the high-doped GaP layer 3 with a high carbon doping concentration. Specifically, the doping concentration of the transition GaP layer between the first carbon-doped GaP layer 31 and the second carbon-doped GaP layer 32 gradually increases from the first carbon-doped GaP layer 31 to the second carbon-doped GaP layer 32, and the doping concentration of the transition GaP layer between the third carbon-doped GaP layer 33 and the fourth carbon-doped GaP layer 34 gradually increases from the third carbon-doped GaP layer 33 to the fourth carbon-doped GaP layer 34. In a specific implementation, the multiple transition GaP layers are 3e1cm -3 A step gradually transitions from the side of the highly doped GaP layer 3 with low carbon doping concentration to the side of the highly doped GaP layer 3 with high carbon doping concentration until it transitions to the target concentration of the carbon-doped GaP layer with higher doping concentration. The growth thickness of multiple transition GaP layers is 1000A in total.

[0036] In this embodiment, the reflective layer 4 includes a dielectric layer and a metal mirror layer 43. The dielectric layer is arranged on a side close to the highly doped GaP layer 3. A first SiO 2 Layer 41, in the first SiO 2 A CB hole 410 is etched on the first SiO 2 The second SiO layer is grown on layer 41. 2 A mirror metal is evaporated on the surface of the dielectric layer away from the highly doped GaP layer 3 to form a mirror metal layer 43, wherein the mirror metal includes but is not limited to Au, Ag or Al.

[0037] It can be understood that by 2 After etching the CB hole on the layer, a second SiO 2 Layer, first SiO 2 Layer and second SiO 2 The layer is combined into a new dielectric layer, and then forms an ODR (omnidirectional reflector) structure with the metal mirror layer. This prevents light from being absorbed by the epitaxial layer after passing through the CB hole, and because there is also SiO in the CB hole, 2 , which can reflect light to a certain degree of ODR, further improving the light output efficiency of the LED chip.

[0038] Example 2

[0039] See also Figure 2 , is a method for preparing a red-yellow GaAs LED chip provided in a second embodiment of the present invention, which is used to prepare the LED chip in the first embodiment above, and the method comprises steps S20 to S23:

[0040] Step S20, providing a GaAs substrate;

[0041] Step S21, growing an epitaxial layer on the GaAs substrate;

[0042] By way of example and not limitation, as an embodiment of an epitaxial layer,

[0043] Growing GaAs as a buffer layer on a GaAs substrate layer;

[0044] Growing GaInP on the buffer layer as a cutoff layer;

[0045] Growing GaAs on the cutoff layer as an N-contact layer;

[0046] Growing GaInP on the N-contact layer as an N-transition layer;

[0047] Growing AlxGaInP on the N-transition layer as an N-current spreading layer;

[0048] N-AlInP is grown on the N-current spreading layer to provide electrons;

[0049] Growing AlGaInP as an N-barrier layer on the N-AlInP layer;

[0050] Growing an MQW quantum well on the N-barrier layer as a light-emitting layer;

[0051] AlGaInP is grown on the MQW quantum well as a P-barrier layer;

[0052] Growing P-AlInP on the P-barrier layer to provide holes;

[0053] AlGaInP is grown on P-AlInP as a transition layer.

[0054] Step S22, sequentially growing a first carbon-doped GaP layer on the epitaxial layer, then growing a transition GaP layer, then continuing to grow a second carbon-doped GaP layer, then growing a transition GaP layer, then continuing to grow a third carbon-doped GaP layer, and finally growing a fourth carbon-doped GaP layer;

[0055] Correspondingly, the first carbon-doped GaP layer is grown on the transition layer, then the transition GaP layer is grown, then the second carbon-doped GaP layer is grown, then the transition GaP layer is grown, then the third carbon-doped GaP layer is grown, and finally the fourth carbon-doped GaP layer is grown; in the specific implementation, the epitaxial layer is grown in sequence with a doping concentration of 3e16cm -3 The first carbon-doped GaP layer is then grown every 3e1cm -3 A step transition to 3e17cm -3 The transition GaP layer is then grown with a doping concentration of 3e17cm -3 The second carbon-doped GaP layer is then grown every 3e1cm -3 A step transition to 5e18cm -3 The transition GaP layer is then grown with a doping concentration of 5e18cm -3 The third carbon-doped GaP layer is grown with a final doping concentration of 5e20cm -3 A fourth carbon-doped GaP layer.

[0056] Step S23, growing a first SiO2 layer as a CB layer on the fourth carbon-doped GaP layer, photolithography a CB pattern on the CB layer, wet etching a CB hole, and then growing a second SiO2 layer on the first CB layer.

[0057] Specifically, PECVD was used to grow the first SiO 2 As the CB layer, the CB pattern is photolithographically formed, and a second SiO layer of 10A-15A is grown using ALD or PECVD.2 layer.

[0058] In summary, the red-yellow GaAs LED chip and preparation method in the embodiments of the present invention are provided with a highly doped GaP layer on the P-type layer. Without the annealing process, although the mirror metal layer and the GaP layer should be in Schottky contact, the present invention utilizes the tunnel effect. Through the extremely thin GaP layer with a high doping concentration, the potential barrier between the semiconductor and the metal is extremely thin, and the relative carrier concentration is extremely high. When excited, the carriers can directly pass through the potential barrier instead of crossing the potential barrier, so that the chip can achieve ohmic contact without annealing, thereby avoiding the problem of reduced light output efficiency of the LED chip caused by fusion exchange between the mirror metal and the epitaxial layer after annealing, thereby improving the luminous efficiency of the LED chip.

[0059] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A red-yellow GaAs LED chip, characterized in that: It comprises a GaAs substrate, an epitaxial layer, a highly doped GaP layer and a reflective layer which are stacked in sequence, wherein the highly doped GaP layer comprises a first carbon-doped GaP layer, a second carbon-doped GaP layer, a third carbon-doped GaP layer and a fourth carbon-doped GaP layer which are sequentially arranged, wherein the first carbon-doped GaP layer is arranged on a side close to the epitaxial layer, and a plurality of transition GaP layers are arranged between the first carbon-doped GaP layer and the second carbon-doped GaP layer, and between the second carbon-doped GaP layer and the third carbon-doped GaP layer, wherein the reflective layer comprises a dielectric layer and a metal mirror layer, and wherein the dielectric layer is arranged on a side close to the highly doped GaP layer; Wherein, a first SiO2 layer is grown on the highly doped GaP layer, CB holes are etched on the first SiO2 layer, and then a second SiO2 layer is grown to form the dielectric layer; The carbon doping concentration of the first carbon-doped GaP layer is 3e16cm -3 The doping concentration of the second carbon-doped GaP layer is 3e17cm -3 The doping concentration of the third carbon-doped GaP layer is 5e18cm -3 The doping concentration of the fourth carbon-doped GaP layer is 5e20cm -3 ; The growth thickness of the first carbon-doped GaP layer is 5000A, the growth thickness of the second carbon-doped GaP layer is 3000A, the growth thickness of the third carbon-doped GaP layer is 3000A, and the growth thickness of the fourth carbon-doped GaP layer is 100A-300A.

2. The red-yellow GaAs LED chip according to claim 1, characterized in that: The carbon doping concentrations of the multiple transition GaP layers gradually increase from the side of the highly doped GaP layer with a low carbon doping concentration to the side of the highly doped GaP layer with a high carbon doping concentration.

3. The red-yellow GaAs LED chip according to claim 2, characterized in that: The multiple transition GaP layers are 3e1cm -3 A step gradually transitions from a side of the highly-doped GaP layer with a low carbon doping concentration to a side of the highly-doped GaP layer with a high carbon doping concentration.

4. The red-yellow GaAs LED chip according to claim 1, characterized in that: The total growth thickness of the multiple transition GaP layers is 1000A.

5. The red-yellow GaAs LED chip according to claim 4, characterized in that: A mirror metal is evaporated on a surface of the dielectric layer at a side away from the highly-doped GaP layer to form the mirror metal layer.

6. A method for preparing a red-yellow GaAs LED chip, characterized in that: A method for preparing a red-yellow GaAs LED chip according to any one of claims 1 to 5, comprising: Providing a GaAs substrate; growing an epitaxial layer on the GaAs substrate; On the epitaxial layer, sequentially grow a first carbon-doped GaP layer, then grow a transition GaP layer, then continue to grow a second carbon-doped GaP layer, then grow a transition GaP layer, then continue to grow a third carbon-doped GaP layer, and finally grow a fourth carbon-doped GaP layer; A first SiO2 layer is grown on the fourth carbon-doped GaP layer as a CB layer, a CB pattern is photolithographically formed on the CB layer, and then a CB hole is wet-etched, and then a second SiO2 layer is grown on the CB layer.

7. The method for preparing a red-yellow GaAs LED chip according to claim 6, characterized in that: The steps of sequentially growing a first carbon-doped GaP layer, then growing a transition GaP layer, then continuing to grow a second carbon-doped GaP layer, then growing a transition GaP layer, then continuing to grow a third carbon-doped GaP layer, and finally growing a fourth carbon-doped GaP layer on the epitaxial layer include: The epitaxial layer is sequentially grown with a doping concentration of 3e16cm -3 The first carbon-doped GaP layer is then grown every 3e1cm -3 A step transition to 3e17cm -3 The transition GaP layer is then grown with a doping concentration of 3e17cm -3 The second carbon-doped GaP layer is then grown every 3e1 -3 A step transition to 5e18cm -3 The transition GaP layer is then grown with a doping concentration of 5e18cm -3 The third carbon-doped GaP layer is grown with a final doping concentration of 5e20cm -3 A fourth carbon-doped GaP layer.

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