TWI674681B - Light emitting diode device and superlattice - Google Patents

Abstract

A light emitting diode element includes a first type doped semiconductor layer, a light emitting layer, a second type doped semiconductor layer, and a superlattice layer. The light emitting layer is located between the first type doped semiconductor layer and the second type doped semiconductor layer. The superlattice layer is located between the first type doped semiconductor layer and the light-emitting layer, wherein the superlattice layer includes a plurality of stacked repeating units, and each of the repeating units includes an Al _x1 In _y Ga _1-x1-y N Layer, a GaN layer, and an In _x2 Ga _1-x2 N layer, where 0.01 ≤ x ₁ ≤ 0.15 and 0.01 ≤ y ≤ 0.15. The GaN layer is located between the Al _x1 In _y Ga _1-x1-y N layer and the first-type doped semiconductor layer. The In _x2 Ga _1-x2 N layer is located between the Al _x1 In _y Ga _1-x1-y N layer and the light emitting layer, where 0.01 <x ₂ ≤ 0.3.

Description

Light-emitting diode element and superlattice layer

The invention relates to a light-emitting diode device (Light-Emitting Diode, LED), and in particular to a light-emitting diode device with a superlattice layer.

The light-emitting diode element has a super-lattice layer between the N-type semiconductor layer and the light-emitting layer. The superlattice layer is used to reduce the residual stress caused by the lattice mismatch, which can reduce the interface defect density of the epitaxial structure. Generally, a superlattice layer is made up of two layers of semiconductor material stacked in pairs. The more commonly used materials are, for example, aluminum gallium nitride / gallium nitride (AlGaN / GaN) or indium gallium nitride / indium gallium nitride (In _x1Ga1-x1 N / In _{x2Ga1- x2} N). Although the above-mentioned superlattice layer composed of multiple pairs of two stacked semiconductor material layers can reduce stress accumulation and improve the epitaxial quality of a light emitting diode device, it is composed of multiple pairs of stacked two semiconductor material layers. The superlattice layer has gradually faced a bottleneck in improving the quality of the epitaxial layer. Therefore, how to further improve the quality of the epitaxial layer to enhance the photoelectric characteristics of the light emitting diode device is one of the topics that the current R & D personnel are eager to seek a breakthrough.

The invention provides a superlattice layer having a good stress buffering effect and a light emitting diode element having the superlattice layer.

The invention provides a light-emitting diode element, which includes a first-type doped semiconductor layer, a light-emitting layer, a second-type doped semiconductor layer, and a superlattice layer. The light emitting layer is located between the first type doped semiconductor layer and the second type doped semiconductor layer. The superlattice layer is located between the first type doped semiconductor layer and the light-emitting layer. The superlattice layer includes a plurality of stacked repeating units, each of which includes an Al _x1 In _y Ga _{1- An x1-y} N layer, a GaN layer, and an In _x2Ga1-x2 N layer, where 0.01 ≤ x ₁ ≤ 0.15 and 0.01 ≤ y ≤ 0.15. The GaN layer is located between the Al _x1 In _y Ga _1-x1-y N layer and the first-type doped semiconductor layer. The In _x2Ga1-x2 N layer is located between the Al _x1 In _y Ga _1-x1-y N layer and the light emitting layer, where 0.01 <x ₂ ≤ 0.3.

The invention further provides a superlattice layer, which includes a plurality of stacked repeating units, and each of the repeating units includes an Al _x1 In _y Ga _1-x1-y N layer, a GaN layer, and an In _x2Ga1-x2 N Layer, where 0.01 ≤ x ₁ ≤ 0.15 and 0.01 ≤ y ≤ 0.15. The GaN layer is located between the Al _x1 In _y Ga _1-x1-y N layer and the first-type doped semiconductor layer. The In _x2Ga1-x2 N layer is located between the Al _x1 In _y Ga _1-x1-y N layer and the light emitting layer, where 0.01 <x ₂ ≤ 0.3.

In an embodiment of the present invention, the number of the repeating units is between 2 and 20.

In an embodiment of the present invention, the thickness of each of the Al _x1 In _y Ga _1-x1-y N layers is between 0.1 nm and 1 nm.

In an embodiment of the present invention, the thickness of each of the GaN layers is between 1 nm and 5 nm.

In an embodiment of the present invention, the thickness of each of the above In _x2Ga1-x2 N layers is between 0.5 nm and 2 nm.

In an embodiment of the present invention, the thickness of each GaN layer is T1, the thickness of each Al _x1 In _y Ga _1-x1-y N layer is T2, and the thickness of each In _x2Ga1-x2 N layer is T3, and T1 / (T2 + T3) is between 0.3 and 10.

In an embodiment of the present invention, the thickness of each Al _x1 In _y Ga _1-x1-y N layer is T2, and the thickness of each In _x2Ga1-x2 N layer is T3, and T3 / T2 ranges from 0.4 to Between 50.

In an embodiment of the present invention, the light-emitting layer includes a plurality of quantum well layers and a plurality of quantum barrier layers that are alternately stacked, and the thickness of the quantum barrier layer in contact with the first-type doped semiconductor layer is between 5 and 5. Nano to 20 nano.

In an embodiment of the present invention, the repeating unit further includes a graded layer, and the graded layer is located between the In _x2Ga1-x2 N layer and the GaN layer.

In an embodiment of the present invention, the above-mentioned graded layer is an In _x3Ga1-x3 N layer with graded In content, and along the thickness direction, x ₃ changes from 0 to x ₂ .

In an embodiment of the present invention, the above-described graded layer is the In content a graded _{In x3Ga1-x3} N layer along the thickness direction, and x ₃ from (x _2/2) is graded x _2.

In an embodiment of the present invention, the thickness of the gradient layer is between 0.1 nm and 2 nm.

In an embodiment of the present invention, the thickness of each of the above In _x2Ga1-x2 N layers is T3, and the thickness of each graded layer is T4, and (T3 / T4) is between 0.1 and 60.

In an embodiment of the present invention, the thickness of the superlattice layer is between 1.5 nm and 10 nm.

In an embodiment of the present invention, the total thickness of the repeating units is between 3 nm and 200 nm.

Based on the foregoing, the light-emitting diode element in the foregoing embodiment is a superlattice layer formed by alternately stacking three or more material layers to improve the quality of the epitaxial crystal and further improve the photoelectric characteristics of the light-emitting diode element.

In order to make the above features and advantages of the present invention more comprehensible, embodiments are hereinafter described in detail with reference to the accompanying drawings.

FIG. 1A is a cross-sectional view of a light emitting diode device according to an embodiment of the present invention. Referring to FIG. 1A, in this embodiment, the light emitting diode device 100a includes a first type doped semiconductor layer 110, a light emitting layer 120, a second type doped semiconductor layer 130, and a superlattice layer 140a. In this embodiment, the first type doped semiconductor layer 110 is an N-type gallium nitride layer, and the second type doped semiconductor layer 130 is a P-type gallium nitride layer. The light emitting layer 120 is located between the first type doped semiconductor layer 110 and the second type doped semiconductor layer 130. The superlattice layer 140a is located between the first type doped semiconductor layer 110 and the light emitting layer 120. The superlattice layer 140a includes a plurality of stacked repeating units 140a1 (stacked repeating units), and each repeating unit 140a1 includes an In _{x2Ga1 -x2} N layer 142, an _{Al x1 In y Ga 1-x1} -y N layer 144 and the GaN layer 146. The ranges of x1 and y in the Al _x1 In _y Ga _1-x1-y N layer are 0.01 ≤ x ₁ ≤ 0.15 and 0.01 ≤ y ≤ 0.15, respectively. The GaN layer 146 is located between the Al _x1 In _y Ga _1-x1-y N layer 144 and the first-type doped semiconductor layer 110. The In _x2Ga1-x2 N layer 142 is located between the Al _x1 In _y Ga _1-x1-y N layer 144 and the light emitting layer 120, where the range of x2 is 0.01 <x ₂ ≤ 0.3.

In this embodiment, the number of the plurality of repeating units 140a1 in the superlattice layer 140a is between 2 and 20. In one embodiment, the number of the repeating units 140a1 in the superlattice layer 140a is, for example, six.

It should be noted that in the present _embodiment, In _x2Ga1-x2 N layer _{142, Al x1 In y Ga 1} -x1-y N layer 144 and the thickness of the GaN layer 146 are T1, T2 and T3. The thickness T1 of each In _x2Ga1-x2 N layer 142 is, for example, between 0.5 nm and 2 nm, and the thickness T2 of each Al _x1 In _y Ga _1-x1-y N layer 144 is, for example, between 0.1 nm and 1 nm, and the thickness of each GaN layer 146 is, for example, between 1 nm and 5 nm.

In this embodiment, the ratio of T1 / (T2 + T3) is, for example, between 0.3 and 10, and the ratio of T3 / T2 is, for example, between 0.4 and 50.

In this embodiment, the light emitting diode device 100 a may further include a substrate SUB, an undoped gallium nitride layer 150 (u-GaN, undoped-GaN), and a buffer layer 160. The undoped gallium nitride layer 150 is located between the substrate SUB and the buffer layer 160. The first type doped semiconductor layer 110 is located on the undoped gallium nitride layer 150. The material of the substrate SUB is, for example, C-Plane, R-Plane, or A-Plane alumina single crystal (Sapphire) or other transparent materials. In addition, single crystal compounds having a lattice constant close to that of a nitride semiconductor are also suitable as a material for the substrate SUB. It is worth noting that the buffer layer 160 is usually formed on the substrate SUB before the first type doped semiconductor layer 110 is fabricated. In other words, the buffer layer 160 can be selectively formed between the substrate SUB and the first-type doped semiconductor layer 110 to provide appropriate stress relief and improve the epitaxial quality of the subsequently formed thin film. The material of the buffer layer 160 is nitrogen Aluminum gallium (AlGaN) or gallium nitride (GaN).

In this embodiment, the light emitting layer 120 is a multiple quantum well structure (Mutiple Quantum Well, MQW), where the multiple quantum well structure includes a plurality of quantum well layers 122 (Well) and a plurality of quantum barriers which are alternately arranged in a repeating manner. Layer 124 (Barrier). In this embodiment, the thickness of the quantum barrier layer 124 in contact with the first-type doped semiconductor layer 110 is between 5 nm and 20 nm.

It must be noted here that the following embodiments use the component numbers and parts of the foregoing embodiments, in which the same reference numerals are used to indicate the same or similar components, and the description of the same technical content is omitted. For the description of the omitted parts, reference may be made to the foregoing embodiments, and the following embodiments are not repeated.

FIG. 1B is a cross-sectional view of a light emitting diode device according to another embodiment of the present invention. Please refer to FIG. 1B. The main difference between the light-emitting diode element 100b in this embodiment and the light-emitting diode element 100a in the previous embodiment is that in addition to the In _x2Ga1-x2 N layer 142, Al _x1 In _y Ga _{1-x1 In addition to the -y} N layer 144 and the GaN layer 146, the repeating unit 140b1 in this embodiment further includes a graded layer 148, where the graded layer 148 is located between the _Inx2Ga1-x2 N layer 142 and the GaN layer 146. Specifically, the graded layer 148 is located between the In _x2Ga1-x2 N layer 142 and the Al _x1 In _y Ga _1-x1-y N layer 144.

Compared with the light-emitting diode element without a superlattice layer, the light-emitting diode element 100b in this embodiment can increase the light-emitting brightness by 1% to 2%, and the forward voltage (Vf) can be reduced by 0.03V. In addition, In the test of the electrostatic discharge (ESD) of the light-emitting diode element 100b in this embodiment, the ratio of passing the test is increased by 2%.

It should be noted that, in this embodiment, the thickness of the graded layer 148 is T4, where T4 is between 0.1 nm and 2 nm. Further, the ratio of T3 / T4 is between 0.1 and 60. Specifically, the number of these repeating units 140b1 is six, and the thickness is 21 nm. Further, the thickness of each repeating unit 140b1 is 3.5 nm, where the thickness of the In _x2Ga1-x2 N layer 142 and the gradient layer 148 is 2.15 nm, and the thickness of the Al _x1 In _y Ga _1-x1-y N layer 144 is, for example, The thickness is 0.35 nm, and the thickness of the GaN layer 146 is, for example, 1 nm.

In another embodiment of the present invention, the graded layer 148 is an In _x3Ga1-x3 N layer with a graded In content. Preferably, along a thickness direction D, the In content x3 thereof changes from 0 to x2. In other embodiments, the In content x3 may be changed from (x2 / 2) to x2 along the thickness direction D.

It should be noted that the thickness of the superlattice layers 140a, 140b in the above embodiment is between 3.2 nm and 200 nm. In addition, the total thickness of these repeating units is between 1.6 nm and 10 nm.

FIG. 2 is a concentration distribution diagram of different elements of the light emitting diode element 100b with respect to thickness according to an embodiment of the present invention. It is worth noting that the selected part of the frame is the distribution map of different element concentrations versus thicknesses of the superlattice layer 140a. The concentration range of aluminum (Al) is about 2 x 10 ²⁴ atoms / cm ³ to 3 x 10 ²⁴ Atom / cm ³ .

In summary, the light-emitting diode element of the present invention can improve the quality of the epitaxial layer and the photoelectric characteristics of the light-emitting diode element through superlattice layers stacked alternately with three or more layers.

Although the present invention has been disclosed as above with the examples, it is not intended to limit the present invention. Any person with ordinary knowledge in the technical field can make some modifications and retouching without departing from the spirit and scope of the present invention. The protection scope of the present invention shall be determined by the scope of the attached patent application.

100a, 100b, 100c ‧‧‧ light emitting diode element

110‧‧‧type I doped semiconductor layer

120‧‧‧Light-emitting layer

122‧‧‧ Quantum Well Formation

124‧‧‧ Quantum barrier layer

130‧‧‧Second type doped semiconductor layer

140a, 140b‧‧‧ Superlattice layer

140a1, 140b1‧‧‧ repeated units

142‧‧‧In _x2 Ga _1-x2 N layer

144‧‧‧Al _x1 In _y Ga _1-x1-y N layer

146‧‧‧GaN layer

150‧‧‧ undoped gallium nitride layer

160‧‧‧Buffer layer

SUB‧‧‧ substrate

T1, T2, T3, T4‧‧‧thickness

D‧‧‧thickness direction

1A to 1B are cross-sectional views of light emitting diode elements according to different embodiments of the present invention. FIG. 2 is a concentration distribution diagram of different elements of the light emitting diode element with respect to thickness according to an embodiment of the present invention.

Claims (8)

A light emitting diode element includes: a first type doped semiconductor layer; a light emitting layer; and a second type doped semiconductor layer, wherein the light emitting layer is located between the first type doped semiconductor layer and the second type doped semiconductor layer. Between the hetero-semiconductor layers; and a superlattice layer between the first-type doped semiconductor layer and the light-emitting layer, wherein the superlattice layer includes a plurality of stacked repeating units, and Each of the repeating units includes: an AlInGaN-based layer; an GaN-based layer between the AlInGaN-based layer and the first-type doped semiconductor layer; an InGaN-based layer (InGaN based layer) between the AlInGaN-based layer and the light-emitting layer; and a graded layer between the InGaN-based layer and the GaN-based layer, where the thickness of each InGaN-based layer is T3, and each of the graded layers The thickness is T4, and (T3 / T4) is between 0.1 and 60. A light-emitting diode element includes: a superlattice layer including a plurality of stacked repeating units, and each of the repeating units includes: an AlInGaN-based layer; and a GaN-based layer between the AlInGaN-based layer and the first Type I doped half Between the conductor layers; an InGaN-based layer between the AlInGaN-based layer and the light-emitting layer; and a graded layer between the InGaN-based layer and the GaN-based layer, wherein the thickness of each InGaN-based layer is T3 The thickness of each gradient layer is T4, and (T3 / T4) is between 0.1 and 60. The light-emitting diode device according to item 1 or 2 of the scope of patent application, wherein the number of the repeating units is between 2 and 20. The light-emitting diode device according to item 1 or 2 of the scope of the patent application, wherein the thickness of each GaN-based layer is T1, the thickness of each AlInGaN-based layer is T2, and the thickness of each InGaN-based layer is T3 And T1 / (T2 + T3) is between 0.3 and 10. The light-emitting diode device according to item 1 or 2 of the patent application scope, wherein the thickness of each AlInGaN-based layer is T2, and the thickness of each InGaN-based layer is T3, and T3 / T2 is between 0.4 and 50. between. The light-emitting diode device according to item 1 or 2 of the scope of the patent application, wherein each of the graded layers is an In _x Ga _1-x N layer with a graded In content, and along the thickness direction, x changes from 0 to 0.01 <x 0.3. The light-emitting diode device according to item 1 or 2 of the scope of patent application, wherein each of the graded layers is an In _x Ga _1-x N layer with graded In content, and along the thickness direction, x ranges from 0.005 <x 0.15 gradient to 0.01 <x 0.3. The light-emitting diode device according to item 1 or 2 of the scope of patent application, wherein the thickness of the superlattice layer is between 3.2 nm and 200 nm.