KR102018688B1 - An infrared light-emitting diode having an active layer including a deformation-compensating quantum barrier layer and a buffer layer and a manufacturing method thereof - Google Patents

Abstract

The present invention relates to an infrared light emitting diode and a method of manufacturing the same, and more particularly, to an infrared light emitting diode and a method of manufacturing the improved luminous efficiency.
The light emitting diode according to the present invention is an infrared light emitting diode having a center wavelength of 940 nm, characterized in that it has an active layer including an InGaAs layer, an AlGaAs layer, and a GaAsP layer.

Description

An infrared light-emitting diode having an active layer including a deformation-compensating quantum barrier layer and a buffer layer and a manufacturing method

The present invention relates to an infrared light emitting diode and a method of manufacturing the same, and more particularly, to an infrared light emitting diode and a method of manufacturing the improved luminous efficiency through the correction of deformation.

An infrared light emitting diode having a 940 ± 10 nm center wavelength (hereinafter, referred to as a 940 nm center wavelength) has almost the same lattice constant on a GaAs (8) substrate having a high lattice matching ratio and a high cost reduction (economy), as shown in FIG. Grown an n-type Al x Ga 1-x As (7) material and a p-type Al x Ga 1-x As (3) material (0.1 <x <0.7), and between the n-type and p-type materials, an undoped GaAs quantum barrier (5) and these layers ( n-type, p-type, or quantum barrier) to have an active layer 4 including InGaAs quantum well 6 whose In content is adjusted to 10% or less. In general, the active layer 4 has a multi-layer structure composed of InGaAs quantum wells 6 and GaAs quantum barriers 5. In addition, in order to maximize the light efficiency, the p-type window 2 layer for the current diffusion layer is grown on the uppermost portion of 3um or more. The upper electrode 1 is formed on the upper portion of the p-type window 2, and the lower electrode 9 is formed on the lower portion of the GaAs substrate 8. Infrared light emitting diodes having a 940 nm center wavelength are generally manufactured using MOCVD for high quality growth.

However, this structure causes the InGaAs, which is used as the quantum well of the active layer, to be deformed due to lattice mismatch with the GaAs layer during the growth process, causing a decrease in efficiency.

The problem to be solved by the present invention is to provide a method for improving the efficiency degradation due to the lattice mismatch of the infrared light emitting diode having a 940nm center wavelength.

Another problem to be solved by the present invention is to provide a light emitting diode having improved efficiency by solving the lattice mismatch of the infrared light emitting diode having a 940nm center wavelength.

In order to solve the above problems,

An infrared light emitting diode having a 940 nm center wavelength according to the present invention is characterized by having an active layer including an InGaAs layer, a GaAsP layer, and an AlGaAs layer.

In the present invention, the AlGaAs layer is preferably located between the InGaAs layer and the GaAsP layer to mitigate the abrupt deformation change between the InGaAs layer and the GaAsP layer.

It is theoretically limited to but, n-type confining layer, p-type confining layer, and a window layer, while substantially matching a GaAs substrate material and a lattice constant (for _{example, Al 0 3 Ga 0 7 As} / GaAs:.. △ a / a≤ +400 ppm [compressive strain]; the lattice constant strain between the GaAs substrate and the quantum well InGaAs layer has a high compressive strain (for example, In _0.07 Ga _0.93 As / GaAs: Δ a / a≥ +6,000 ppm [compressive strain]; the variation in lattice constant) and the GaAsP tensile quantum barrier layer to compensate for the compressive strain of InGaAs to compensate for the compressive strain generated during the growth of the InGaAs quantum well layer. To improve the efficiency of the active layer of the light emitting diode, an AlGaAs buffer layer having a low compressive strain is introduced between the InGaAs layer and the GaAsP layer to improve the luminous efficiency. do.

In the present invention, the term InGaAs layer is understood to mean a layer consisting substantially of In, Ga, and As.

In the present invention, the term GaAsP layer is understood to mean a layer consisting substantially of Ga, As, and P.

In the present invention, the term AlGaAs layer is understood to mean a layer consisting substantially of Al, Ga, and As.

In the present invention, the term 'compressive strain' means having an arcsec lower than that of a GaAs substrate.

In the present invention, the term 'tensile strain' means having an arcsec higher than that of the GaAs substrate.

In the present invention, the infrared light emitting diode having a 940nm center wavelength is a GaAs substrate; A first type AlGaAs lower limiting layer grown on the substrate; An active layer comprising an InGaAs quantum well layer, a GaAaP quantum barrier layer, and an AlGaAs buffer layer between the quantum well layer and the quantum barrier layer grown on the lower limit layer of the first type AlGaAs; A second type AlGaAs upper limiting layer grown on the active layer; And a p-type window layer, and having an upper electrode and a lower electrode on the top and bottom surfaces of the p-type window layer and the GaAs substrate, respectively.

In the present invention, the GaAs substrate is a substrate on which the lower limiting layer is grown, and a lower electrode may be formed on the lower surface of the substrate. In the practice of the present invention, the GaAs substrate may be the same type as the first type AlGaAs lower limiting layer, preferably an n-type GaAs substrate. For example, the n-type GaAs substrate may have a value of 32.9 arcsec.

In the present invention, the AlGaAs lower limiting layer preferably uses the same type as the lower GaAs substrate, and preferably has an arcsec value of substantially the same level as the n-type substrate and an arcsec value ± 0.5 of the n-type substrate. In a preferred embodiment, AlGaAs can adjust the ratio of Al and Ga so that the arcsec value can have substantially the same level as the n-type substrate. For example, AlGaAs may be represented by Al x Ga 1-x As and x may be 0.3.

In the present invention, the active layer may be a multilayer active layer in which an InGaAs quantum well layer, an AlGaAs buffer layer, and a GaAsP quantum barrier layer are repeatedly stacked.

In the present invention, the InGaAs quantum well layer may use a range of 0.05 ≦ _x ≦ 0.1, more preferably 0.07 ≦ _x ≦ 0.08 at In _x Ga _{1 - x} As, so as to emit a central wavelength of 940 nm. It may be slightly adjusted accordingly.

In the present invention, the GaAsP quantum barrier layer has a tensile strain to compensate for the compressive strain of the InGaAs quantum well layer, and preferably GaAs _{1 - y} P _y ( 0.03 ≦ y ≦ 0.09) may be used.

In the practice of the present invention, GaAs _{1 - y} P _y tensile quantum barrier layer is different tensile properties (0.03≤y≤0.09: -1500 ~ -4500ppm [tensile strain]) under Fig _{In x Ga 1 - x As (} 0.07≤ x≤0.08: ~ + + 6000ppm 7000ppm with respect to the compression of the quantum well [compressive strain]) may represent a modified correction effect and thus to improve light efficiency according to the effect, preferably GaAs _{0 .94} to efficiencies as high as in the end product It is recommended to apply P _0.06 (-3000ppm).

In the present invention, the AlGaAs buffer layer may have improved luminous efficiency by eliminating defects due to opposite polarities between the InGaAs quantum well layer and the quantum barrier layer of GaAsP. Preferably, Al _z Ga _{1 - z} As is 0 ≦. z ≦ 0.4, more preferably 0.1 ≦ z ≦ 0.3, most preferably 0.19 ≦ z ≦ 0.21.

In the practice of the present invention, the active layer may be an InGaAs quantum well layer, a GaAsP quantum barrier layer, and an AlGaAs buffer layer two or more times, preferably three or more times, more preferably four or more times, and preferably five times. Can be stacked.

In the present invention, the upper limiting layer and the lower limiting layer AlGaAs may be represented by Al x Ga 1-x As, x may be 0.2 to 0.4, preferably substantially 0.3.

In an embodiment of the present invention, the InGaAs quantum well layer and the GaAsP quantum barrier layer in the active layer may have a thickness of about 7 nm to about 14 nm, respectively, and may have a substantially ± 1 nm difference. In addition, the AlGaAs buffer layer in the active layer preferably has a thickness of ± 2 ~ 3 nm range.

In one aspect, a light emitting diode comprising a substrate, a lower limiting layer, an active layer including a quantum barrier layer and a quantum well layer, an upper limiting layer, and a window layer,

The quantum well layer has a compressive strain,

The quantum barrier layer has a tensile strain,

Between the quantum well layer and the quantum barrier layer is characterized by having a buffer layer having a compressive strain smaller than the compressive strain of the quantum well layer.

According to an aspect of the present invention, there is provided a light emitting diode including a substrate, a lower limiting layer, an active layer including a quantum barrier and a quantum well, an upper limiting layer, and a window layer. The present invention provides a method of repeatedly forming a quantum barrier layer having a tensile strain and forming a buffer layer having a compressive strain less than that of the quantum well layer between the quantum well layer and the quantum barrier layer.

In the present invention, the compressive strain of the buffer layer may be 0 to 10%, preferably 1 to 8%, and most preferably 5% of the quantum well layer compressive strain.

According to the present invention, a problem caused by deformation of the quantum well layer of an infrared light emitting diode having a center wavelength of 940 nm using a GaAs substrate having a high lattice matching ratio and high cost reduction (economical efficiency) is solved, thereby improving the light emitting efficiency of the infrared diode. Was provided.

An active layer of the infrared light emitting diode 940nm deformation compensation made in the invention In _0.07 GaAs quantum well and compressed GaAsP _{0 .06} tensile both high non-uniformity deformed condition by improving through the Al _z Ga _1-z As buffer layer on the barrier 20 relative to the Efficiency A high efficiency 940 nm infrared light emitting diode with a% increase was provided.

According to the present invention, defects caused by compressive deformation of a quantum well layer having compressive deformation with respect to a substrate can be solved.

FIG. 1 schematically shows a 940 nm infrared light emitting diode structure having an active layer in which an In _x Ga _{1- x} P quantum well layer and a GaAs quantum barrier layer manufactured by a MOCVD system are alternately stacked in the prior art.
FIG. 2 schematically shows a 940 nm infrared light emitting diode structure having an active layer in which an In _x Ga _{1- x} P quantum well layer and a GaAsP quantum barrier layer manufactured by a MOCVD system are alternately stacked in a comparative embodiment of the present invention.
FIG. 3 schematically illustrates a 940 nm infrared light emitting diode structure having an In _x Ga _{1- x} P quantum well layer, an AlGaAs buffer layer, and an GaAsP quantum barrier layer sequentially stacked according to the present invention.
4A, 4B, and 4C show the structures of the active layers of FIGS. 1, 2, and 3, respectively.
5 is In _{0 . 07} Ga _{0 .} XRD characteristics of GaAs _{1 - y} P _y and GaAs substrates with ₉₃ As quantum well layer and various P composition ratios are shown.
6 In _{0 . 07} Ga _{0 .} XRD characteristics of various Al _z Ga _{1 - z} As layers used as ₉₃ As quantum well layer and buffer layer are shown.
7 is In _{0 . 07} Ga _{0 . 93 As / GaAs 0 .94 P 0.06} Al z Ga 1 in the MQW _- shows the PL (photoluminescense) characteristics for the active layer of a 940nm infrared light-emitting diode is _z As buffer layer is applied.
8 shows PL characteristics of a conventional InGaAs / GaAs active layer, a comparative InGaAs / GaAsP active layer, and an InGaAs / AlGaAs / GaAsP active layer of the present invention.
9 shows optical characteristics of a 940 nm infrared light emitting diode having a conventional InGaAs / GaAs active layer, a comparative InGaAs / GaAsP active layer, and an InGaAs / AlGaAs / GaAsP active layer to which a buffer layer according to the present invention is applied.

Hereinafter, the present invention will be described in detail through examples.

FIG. 3 is a schematic diagram of a 940 nm infrared light emitting diode structure having an In _x Ga _{1- x} P quantum well layer and a GaAsP quantum barrier layer prepared by a MOCVD system, with an active layer having a buffer layer between the quantum well layer and the quantum barrier layer. It is.

As shown in FIG. 3, the 940 nm infrared light emitting diode 10 has a lower n-type GaAs substrate 18 and an Al _0. Grown on the n-type GaAs substrate _{. 3} Ga _{0 .} In _0. N-type restriction layer 17 made of ₇ As and on the n-type restriction layer 17 _{. 07} Ga _{0 . 93} As quantum wells (14) and Al _{0 . 2} Ga _{0 . 8} As the buffer 16 and the GaAs _{0 .94} P _0.06 quantum barrier 15 is then repeated 5 times growing an active layer (20), ₀ Al on the active layer _{20. 3} Ga _{0 .} The p-type limiting layer 13 grown to ₇ As and the Al _0. Grown on the p-type limiting layer 13 with a thickness of 5 μm for the current diffusion effect and the emission cone region expansion effect of the infrared light emitting diode _{. 2} Ga _{0 . It} has a window layer 12 made of ₈ As. A lower electrode 19 made of AuGeNi was formed below the n-type GaAs substrate 18, and an upper electrode 11 made of AuZn was formed on the window layer 12.

5 is In _{0 . 07} Ga _{0 . 93} As GaAs ₁ with a quantum well layer and the composition ratio of various _P-shows the XRD property of the _y P _y quantum barrier layer and a GaAs substrate, Figure 6 is In _{0. 07} Ga _{0 . The} XRD characteristics of the various Al _z Ga _{1 - z} As layers used as the ₉₃ As quantum well layer and the strain correction balance layer are shown.

All layers were grown on a GaAs substrate as a single layer and scanned under omega-2theta conditions. The GaAs substrate (32.9 arcsec) has a compressive strain characteristic when moving in the lower arcsec direction relative to the substrate, and has a tensile strain characteristic when moving in the higher arcsec direction.

In ₀ used as the light emitting quantum well of 940nm infrared light emitting diode _{. 07} Ga _{0 . In the} case of ₉₃ As, it was confirmed that at 32.55 arcsec, it has a considerably high compressive strain (-6000 ppm) for the GaAs criterion (32.9 arcsec). In general, using a quantum well in the crystal defects caused by strain mismatch In _{0. 07} Ga _{0 . 93} As has a considerably high compressive strain, which causes high crystal defects in the light emitting diode active layer.

Such In _{0 . 07} Ga _{0 .} The deformation of the ₉₃ As compressed quantum well can be largely eliminated by application to the quantum barrier GaAs _{1 - y} P _y with various tensile strains used together in the active layer. XRD analysis showed that GaAs _1-y P _y material was characterized by tensile strain (33.05 arcsec: -1500ppm) to tensile strain (33.35 arcsec: -4500ppm) depending on the P ratio.

Additionally, in order to improve the mismatch strain conditions between the high compression strain quantum wells and the high tensile change quantum barriers, the Al _z Ga _{1 - z} As buffer layer was made of GaAs (32.9 arcsec: 0 ppm), Al _0.2 Ga _0.8 As (compressive strain: +300 ppm). ), And Al _{0 . 4} Ga _{0 . It} was confirmed by XRD analysis that it has ₆ As (compressive strain: + 600ppm). These various tensile strain conditions are In _{0 . 07} Ga _{0 .} It can be applied to ₉₃ As compressed quantum wells to verify the strain compensation characteristics to establish optimization conditions.

7 and 8 show In _{0 . 07} Ga _{0 . 93 As / GaAs 0 .94 P 0.06} Al z Ga 1 in the _MQW-z As shows the PL (photoluminescense) characteristics for the active layer of a 940nm infrared light emitting diode deformation compensation balancing layer have been applied.

In FIG. 7, the InGaAs / GaAsP active layer (MQW) has an intensity of about 6.4, and the InGaAs / GaAsP active layer (MQW) having an Al _0.0 GaAs (= GaAs) buffer layer has an increased strength of about 6.8. Al ₀ with increased Al content _{. 2} Ga _{0 . 8} As and Al _{0 . 4} Ga _{0 . 6} PL intensity of InGaAs / GaAsP active layer through the use of a buffer layer As is shown a strength of about 7.7 and 7.3, respectively, the maximum is Al _{0. 2} Ga _{0 .} Obtained when ₈ As buffer layer was applied. Based on these results, the use of the Al _z Ga _{1 - z} As buffer layer is reduced to In _{0 . 07} Ga _{0 . 93} As / GaAs _{0 .94} P _0.06 efficiency of the diode increases to increase the 940nm infrared light emitting diode having an active layer the efficiency is shown as one of the effective ways to side.

FIG. 8 shows PL characteristics of an InGaAs / AlGaAs / GaAsP active layer having a general InGaAs / GaAs active layer, an InGaAs / GaAsP active layer, and a buffer layer. It was confirmed that the active layer with the buffer layer (strain compensation balance layer) had a high strength about 100% higher than that of the general active layer and about 18% increased compared to the InGaAs / GaAsP active layer.

FIG. 9 shows optical characteristics of a 940 nm infrared light emitting diode having a general InGaAs / GaAs active layer, an InGaAs / GaAsP active layer, and an InGaAs / AlGaAs / GaAsP active layer to which a strain compensation balance layer is applied.

The developed infrared light emitting diodes measured current-voltage (I-V) and current-light (I-L) values under a current value applied up to about 60mA. A relatively high value (7.2 mW) was observed in a 940 nm infrared light emitting diode with an InGaAs / AlGaAs / GaAsP active layer with a buffer layer (strain compensation layer), and a typical InGaAs / GaAs active layer and an InGaAs / GaAsP active layer with a tensile quantum barrier. The optical properties of 4.8mW and 6.2mW are shown for the light emitting diodes with excitation.

As a result, it was confirmed that the efficiency of the 940 nm infrared light emitting diode can be greatly increased by applying the strain compensation balance layer.

10: light emitting diode
11: upper electrode
12: window layer
13: p type limiting layer
14: Quantum Well
15: Quantum Barrier
16: buffer layer (strain compensation balance layer)
17: n-type limiting layer
18: substrate
19: lower electrode
20: active layer

Claims (11)

An active layer including an InGaAs layer, an AlGaAs layer, and a GaAsP layer,
The active layer is an infrared light emitting diode having a 940nm wavelength, characterized in that the AlGaAs layer between the InGaAs layer and GaAsP layer. delete The method of claim 1,
GaAs substrates;
A first type AlGaAs lower limiting layer grown on the substrate;
The active layer in which the InGaAs layer, the AlGaAs layer, and the GaAsP layer are repeatedly stacked on the lower limit layer of the first type AlGaAs;
The upper limiting layer of AlGaAs type 2 grown on the active layer;
A p-type window grown on the upper limiting layer; And
An infrared light emitting diode having a center wavelength of 940 nm, comprising electrodes. The method according to claim 1 or 3,
The InGaAs is an infrared light emitting diode having a center wavelength of 940 nm, characterized in that represented by In _x Ga _1-x As (0.05≤x≤0.1). The method according to claim 1 or 3,
The GaAsP layer is an infrared light emitting diode having a central wavelength of 940 nm, characterized in that GaAs _1-y P _y (0.03≤y≤0.09). The method according to claim 1 or 3,
The AlGaAs layer is an infrared light emitting diode having a center wavelength of 940 nm, characterized in that Al _z Ga _1-z As (0≤z≤0.4). The method according to claim 1 or 3,
InGaAs layer is In _x Ga _1-x As 0.07≤x≤0.08,
GaAsP layer is GaAs _1-y P _y (y = 0.06),
AlGaAs layer is Al _z Ga _1-z As (z = 0.2)
An infrared light emitting diode having a 940 nm center wavelength. The method according to claim 1 or 3,
The active layer is an infrared light emitting diode having a central wavelength of 940nm, characterized in that the InGaAs layer, GaAsP layer and AlGaAs layer is repeatedly stacked 2 to 5 times. delete delete delete

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