KR20210010777A - An optical element having a broadband reflective layer and a manufacturing method thereof - Google Patents

Abstract

The present invention relates to an infrared light emitting diode having a broadband reflective layer and a manufacturing method thereof and, more particularly, to an infrared light emitting diode having a broadband distributed Bragg reflective (DBR) layer and a manufacturing method thereof. Moreover, provided is a new DBR which can reflect a wide range of light. The broadband DBR comprises a first DBR, a second DBR, a third DBR, a first separation layer, and a second separation layer.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention An optical element having a broadband reflective layer and a manufacturing method thereof

The present invention relates to an infrared light emitting diode having a broadband reflective layer and a method of manufacturing the same, and more particularly, to an infrared light emitting diode having a broadband dispersed Bragg reflective layer and a method of manufacturing the same.

The light emitting diode emits light from a PN junction type active layer positioned on the substrate. In order to prevent the efficiency of the light emitting diode from deteriorating due to absorption of light emitted from the active layer downward by the substrate, a light reflecting layer is positioned between the substrate and the active layer.

As one of the light reflecting layers, a Distributed Bragg Reflective ("DBR") that reflects light by repeatedly growing a high-refractive-index material and a low-refractive-index material is used.

DBR can be formed by the same method of growing the active layer on the substrate, for example, MOCVD, and has the advantage of excellent thermal stability after growth, but unlike a metal layer having excellent reflectance for various wavelengths, a specific wavelength range ( Typically, the reflectance is excellent in the range of ±40 nm from the center wavelength). Accordingly, in order to increase the light efficiency of a light emitting diode using DBR, DBRs having the same peak wavelength and reflection peak wavelength of a light source emitted from the light emitting diode are used.

However, even if the peak wavelengths coincide, since the wavelength width of the light emitted from the active layer is wide except for the laser, there are many lights that are not reflected by the DBR, resulting in a problem of lowering the luminous efficiency.

In addition, when light-emitting diodes having active layers having different peak wavelengths are manufactured through the same device, different DBRs must be formed according to the wavelength range of the light-emitting diodes to be manufactured, thereby increasing the manufacturing cost.

The problem to be solved in the present invention is to provide a new DBR that can reflect broadband light.

Another problem to be solved in the present invention is to provide a new DBR capable of reflecting broadband infrared light.

Another problem to be solved in the present invention is to provide a new light-emitting diode including a DBR capable of reflecting a broadband light.

In order to solve the above problems, the present invention

A first DBR in which a first high refractive index layer and a first low refractive index layer are repeatedly stacked;

A second DBR in which a second high refractive index layer and a second low refractive index layer are repeatedly stacked;

A third DBR in which a third high refractive index layer and a third low refractive index layer are repeatedly stacked;

A first spacing layer positioned between the first DBR and the second BDR; And

It provides a broadband DBR including a second separation layer positioned between the second DBR and the third DBR.

In one aspect of the present invention,

A first DBR in which a first high refractive index layer and a first low refractive index layer are repeatedly stacked;

A second DBR in which a second high refractive index layer and a second low refractive index layer are repeatedly stacked;

A third DBR in which a third high refractive index layer and a third low refractive index layer are repeatedly stacked;

A first spacing layer positioned between the first DBR and the second BDR; And

It provides an optical device including a broadband DBR including a second separation layer positioned between the second DBR and the third DBR.

In one aspect of the present invention,

A first DBR in which a first high refractive index layer and a first low refractive index layer are repeatedly stacked;

A second DBR in which a second high refractive index layer and a second low refractive index layer are repeatedly stacked; And

It provides a broadband DBR including; a first separation layer positioned between the first DBR and the second BDR.

The present invention in one aspect,

Growing a first DBR in which a first high refractive index layer and a first low refractive index layer are repeatedly stacked;

Growing a separation layer on the first DBR; And

Growing a second DBR in which a second high refractive index layer and a second low refractive index layer are repeatedly stacked on the separating layer

It provides a method of manufacturing a broadband DBR comprising a.

Although not limited in theory, when a second DBR having a second central wavelength and a reflective region is directly grown on a first DBR having a first central wavelength and a reflection region, it is negatively hybridized through mutual interference A DBR having a reflective area is formed. Accordingly, by forming a separation layer between the first DBR and the second DBR to prevent negative hybridization, a broadband DBR having a wide reflective area including the first reflective area of the first DBR and the reflective area of the second DBR is formed. To form.

In the present invention, the separating layer is 10 nm or more, preferably 50 nm or more, more preferably 100 nm or more, even more preferably so as to prevent direct contact of DBRs and reduce hybridization due to mutual interference. May have a thickness of 200 nm or more, most preferably 300 nm or more. In the practice of the present invention, the thickness of the spacing layer is preferably maintained at 1000 nm or less so as to prevent hybridization and prevent an increase in Vf due to an increase in thickness.

In the present invention, the separating layer may be a growth layer epitaxially grown so that the reflective area of the DBRs can be widened by being positively hybridized in a separated state while the DBR is separated from each other, although it is not theoretically limited. Preferably, it may be a growth layer epi-grown by the MOCVD method.

In the present invention, the separation layer may be made of a material through which light is not absorbed and transmitted. In the practice of the present invention, the separation layer may be a separation layer having a band gap through which infrared light is transmitted. In one embodiment of the present invention, the separation layer may be GaInP or AlAs.

In the present invention, the first DBR may be a DBR that reflects light of a relatively short wavelength compared to the second DBR. In the practice of the present invention, the first DBR may have a center wavelength in the range of 700 to 800 nm, preferably in the range of 730 to 770 nm.

In one embodiment of the present invention, Al _x Ga _{1 - x} High refractive (InP) / Al _{1 - x} Ga _x Low refractive (InP) may be stacked so that the first DBR may have a central wavelength of 750 nm. Here, the x value may be greater than 0.9, more preferably greater than 0.95, and most preferably x=1.

In the present invention, the second DBR may be a DBR that reflects light having a relatively long wavelength compared to the first DBR and reflects light having a relatively short wavelength compared to the third DBR. In the practice of the present invention, the second DBR may have a center wavelength in the range of 800 to 900 nm, preferably in the range of 830 to 970 nm.

_{Y As (High refractive) / Al} 1 - - In one embodiment of the present invention, wherein the 2 DBR is Al _y Ga ₁ to have a center wavelength of 850nm can be made to _y Ga _y As (Low refractive), wherein The y value may be 0.8<y<0.95, more preferably 0.9<x<0.95.

In the present invention, the third DBR may be a DBR that reflects light of a relatively long wavelength compared to the second DBR. In the practice of the present invention, the third DBR may have a central wavelength in the range of 800 to 900 nm, preferably in the range of 830 to 970 nm.

_{Y As (High refractive) / Al} 1 - - In one embodiment of the present invention, wherein the 3 DBR is Al _y Ga ₁ to have a center wavelength of 940nm can be made to _y Ga _y As (Low refractive), wherein The y value may be 0.8<y<0.95, more preferably 0.9<x<0.95. In a preferred embodiment of the present invention, the third DBR having a center wavelength of 940 nm is made of the same material as the second DBR having a center wavelength of 850 nm, and may be a BDR having a different layer thickness.

According to the present invention, a method of manufacturing a broadband DBR using existing DBRs having a small reflection area has been provided.

Since the broadband DBR manufactured by the present invention can reflect a wide range of wavelengths, one broadband DBR can be used for light emitting diodes of various peak wavelengths.

1 is a cross-sectional view of a light emitting diode according to the present invention.
2 is a diagram showing a stacked structure of a broadband DBR of a light emitting diode according to Example 1 of the present invention.
3 is a diagram showing a reflection spectrum of a broadband DBR according to Example 1 of the present invention.
4 is a diagram showing a stacked structure of a broadband DBR of a light emitting diode according to a second embodiment of the present invention.
5 is a diagram showing a reflection spectrum of a broadband DBR according to Example 2 of the present invention.
6 is a diagram showing a stacked structure of a broadband DBR of a light emitting diode according to Example 3 of the present invention.
7 is a diagram showing a reflection spectrum of a broadband DBR according to Example 3 of the present invention.
8 is a diagram showing a stacked structure of a broadband DBR of a light emitting diode according to Comparative Example 1.
9 is a diagram showing a composite DBR according to Comparative Example 1 and reflection spectra of DBR 1 and DBR 2. FIG.
10 is a diagram showing a stacked structure of a broadband DBR of a light emitting diode according to Comparative Example 2.
11 is a diagram showing a composite DBR according to Comparative Example 2 and reflection spectra of DBR 2 and DBR 3.
12 is a graph showing current-voltage characteristics and light efficiency for Example 1, Comparative Example 1, and DBR 1 of the present invention.

Hereinafter, the present invention will be described in detail through examples. It should be noted that the following examples are intended to illustrate the present invention and are not intended to be limiting.

Example 1

As shown in FIG. 1, the light emitting diode 10 including the broadband DBR according to the present invention includes a broadband DBR 200 grown in a MOCVD method on a substrate 100, and a light emitting diode grown in the broadband DBR 200. A window 400 formed on the part 300 and the light emitting part 300, a lower electrode 510 located on the lower surface of the substrate 100, and an upper electrode located on the upper surface of the window 400 ( 520). The light-emitting unit 300 includes a lower limiting layer 310, an active layer 320, and an upper limiting layer 330, and the active layer 320 forms a PN junction layer in which quantum wells and quantum barriers are repeatedly stacked. Light is emitted from the active layer 320 by a human voltage through the electrode 510 and the upper electrode 520, and the light emitted from the active layer is emitted upwards and downwards, and the light emitted upwards is emitted through the window 400. The light emitted toward the top of the substrate and emitted downward is reflected by the broadband DBR 200 located on the substrate and then emitted in a direction perpendicular to the substrate.

As shown in FIG. 2, the broadband DBR 200 includes a first DBR 210 in which a first high refractive index layer and a first low refractive index layer grown on the substrate 100 are repeatedly stacked; A second DBR 220 in which a second high refractive index layer and a second low refractive index layer are repeatedly stacked; A third DBR 230 in which a third high refractive index layer and a third low refractive index layer are repeatedly stacked; A first separation layer 240 positioned between the first DBR 210 and the second BDR 220; It consists of a second separation layer 250 positioned between the second DBR 220 and the third DBR (230).

The first DBR 210 used AlInP as the high refractive index layer and GaInP as the low refractive index layer, and was repeatedly grown 7 times with a thickness of 40-50 nm (wavelength calculation applied) for each layer by MOCVD method, and the second DBR (220) used AlxGa1-xAs (x=0.95) as the high refractive layer and Al1-xGaxAs (x=0.95) as the low refractive layer, and grown repeatedly 7 times with a thickness of 40 to 60 nm for each layer by MOCVD method. The 3rd DBR 230 uses AlxGa1-xAs (x=0.9) as a high refractive layer, and Al1-xGaxAs (x=0.9) as a low refractive layer, and the thickness of each layer is approximately 50-70 nm by MOCVD method. It was grown repeatedly 7 times. A 100 nm-thick first separation layer 240 made of GaInP was grown between the first DBR 210 and the second DBR 220 by the MOCVD method, and between the second DBR 220 and the third DBR 230 A second separation layer 250 having a thickness of 100 nm made of AlAs was grown by MOCVD.

AlInP/GaInP used as the first DBR 210 has a central wavelength of 750 nm, and AlxGa1-xAs(x=0.95)/Al1-xGaxAs(x=0.05) used as the second DBF (thickness 46 nm/56 nm) ) Has a central wavelength of 850 nm, and AlxGa1-xAs (x= 0.9)/Al1-xGaxAs (x=0.9) (thickness 58 nm/66 nm) used as the third DBR has a central wavelength of 950 nm.

As shown in FIG. 3, the first BDR 210, the second DBR 220, and the third DBR 230 each having a center wavelength of 750 nm, 850 nm, and 950 nm are GaInP first separation layer 240 and AlAs It was confirmed that the dispersed Bragg reflective layer combined with the second spacing layer 150 has a considerably high reflectance for a wide band of about 200 nm from about 750 nm to 950 nm.

Example 2

Having the same structure as in Example 1, and as shown in FIG. 4, the broadband DBR 200 includes a first DBR in which a first high refractive index layer and a first low refractive index layer grown on the substrate 100 are repeatedly stacked ( 210) and; A second DBR 220 in which a second high refractive index layer and a second low refractive index layer are repeatedly stacked; It consists of a first separation layer 240 positioned between the first DBR 210 and the second BDR 220.

The first DBR 210 used AlInP as the high refractive index layer and GaInP as the low refractive index layer, and was repeatedly grown 10 times with a thickness of about AlInP/GaInP = 38 nm/46 nm for each layer by MOCVD method, and the second DBR ( 220) uses AlxGa1-xAs (x= 0.95) as a high refractive layer and Al1-xGaxAs (x= 0.95) as a low refractive layer, and AlxGa1-xAs(x=0.95)/Al1-xGaxAs(x =0.95 ); (46nm/56nm) It was grown repeatedly 10 times. Between the first DBR 210 and the second DBR 220, a first separation layer 240 having a thickness of 100 nm made of GaInP was grown by the MOCVD method.

AlInP/GaInP used as the first DBR 210 has a center wavelength of 750 nm, and AlxGa1-xAs (x= 0.9)/Al1-xGaxAs (x= 0.9) used as the second DBF; (58nm/66nm) has a center wavelength of 850 nm.

As shown in FIG. 5, the dispersed Bragg reflective layer in which the first BDR 210 and the second DBR 220 having central wavelengths of 750 nm and 850 nm are combined with the GaInP first separation layer 240 is from about 750 nm to 850 nm. It was found to have high reflectance for a wide band of about 100 nm. In the case of GaInP, the lattice constant is quite consistent with the DBR II materials, minimizing defects between the two DBRs, and was able to act as a buffer.

Example 3

Having the same structure as in Example 1, and as shown in FIG. 6, the broadband DBR 200 includes a second DBR in which a first high refractive index layer and a first low refractive index layer grown on the substrate 100 are repeatedly stacked ( 220) and; A third DBR 230 in which a second high refractive index layer and a second low refractive index layer are repeatedly stacked; It consists of a second separation layer 250 positioned between the second DBR (220) and the third BDR (230).

The second DBR 220 uses AlxGa1-xAs(x= 0.95) as a high refractive layer and Al1-xGaxAs as a low refractive layer, and AlxGa1-xAs(x= 0.9)/Al1-xGaxAs( x= 0.9); It was repeatedly grown 10 times to a thickness of (58nm/66nm), and the third DBR 230 was AlxGa1-xAs (x= 0.9)/Al1-xGaxAs (x= 0.9); (58nm/66nm) It was grown repeatedly 10 times.

A second separation layer 250 having a thickness of 100 nm made of AlAs was grown between the second DBR 220 and the third DBR 230 by the MOCVD method.

The 2nd DBR and 3rd DBR used the same material, but the central wavelength was adjusted by different thickness.

As shown in FIG. 7, the dispersed Bragg reflective layer in which the second BDR 120 and the third DBR 130 having central wavelengths of 850 nm and 950 nm are combined with the AlAs second separation layer 150 is from about 850 nm to 950 nm. It was found to have high reflectance for a wide band of about 100 nm.

Comparative Example 1

Example 2 was carried out in the same manner as in Example 2 except that the first separation layer 140 was not used and the second BDR 120 was directly grown on the first DBR 110 as shown in FIG. 8.

As shown in FIG. 9, a dispersion Bragg reflective layer with a central wavelength of 750 nm of AlInP/GaInP series made of 20 pairs (red) and an AlxGa1-xAs/Al1-xGaxAs series of AlxGa1-xAs/Al1-xGaxAs made of 20 pairs with a center wavelength of 850 nm dispersed Bragg reflective layer (green ) Shows the reflection spectrum. It shows the reflection spectrum of 750nm DBR I + 850nm DBR II (black) produced by combining the 750nm dispersed Bragg reflective layer and the 850nm dispersed Bragg reflective layer. In the case of such a multi-form dispersion Bragg reflective layer (750nm DBR I + 850nm DBR II), compared to the existing single 750nm diffuse Bragg reflective layer or 850nm diffuse Bragg reflective layer, it did not show significantly improved characteristics, and it was slightly close to 850nm with a center wavelength of 830nm. . As shown in FIG. 8, it was confirmed that the characteristics of the first DBR 110 are negatively hybridized and the characteristics of the second DBR 120 are negatively hybridized.

Comparative Example 2

It was carried out in the same manner as in Example 3 except that the second separation layer 150 was not used and the third BDR 130 was directly grown on the second DBR 120.

The reflection spectrum of the AlxGa1-xAs/Al1-xGaxAs series made with 20 pairs of 850nm center wavelength dispersion Bragg reflective layer (red) and the same material made with 20 pairs of lxGa1-xAs/Al1-xGaxAs series 950nm center wavelength dispersion Bragg reflective layer (green) Shows. In addition, it shows the reflection spectrum of 850nm DBR II + 950nm DBR III (black) fabricated by combining the 850nm dispersed Bragg reflective layer and the 950nm dispersed Bragg reflective layer. The dispersion Bragg reflective layer (850nm DBR II + 950nm DBR III) fabricated in such a multi-shape also did not improve the reflection spectrum compared to the existing single diffused Bragg reflective layers, and the central wavelength shifted to 900nm to slightly closer to 950nm. As shown in FIG. 8, it was confirmed that the characteristics of the second DBR 120 and the characteristics of the third DBR 130 are negatively hybridized.

Comparative Example 3

Except for changing the second separation layer 150 to GaAs in Example 3, it was carried out in the same manner. The second separating layer 150 made of GaAs absorbs light, and reflectance was measured only in the third DBR 130 positioned above the second separating layer 150.

Example 4

A light emitting diode using a broadband DBR (DBR 1 + DBR 2 + DBR 3) according to Example 1, a light emitting diode using a broadband DBR (DBR 2 + DBR 3) according to Example 3, and a DBR consisting of 20 pairs Light-emitting diodes using 2 were prepared. All applied dispersed Bragg reflective layers had the same dopant, and the number of stacked layers was almost the same as a total of 21 pairs, 20 pairs, and 20 pairs, and there was no significant difference in current-voltage characteristics.

On the other hand, in the case of light efficiency, it shows quite different results. When the single dispersion Bragg reflective layer (DBR 2) was applied, the light efficiency was about 14.3 mW at 100 mA, and when the broadband DBR (DBR 2 + DBR 3) according to Example 3 was applied, the light efficiency increased by about 15% to about 16.5 mW. Is showing. Additionally, when the broadband DBR (DBR 1 + DBR 2 + DBR 3) according to Example 1 is applied, a relatively high value of about 20.5 is increased by 43%.

Through these results, it was confirmed that a reflective layer having a wider spectrum of reflection spectrum can effectively increase the optical efficiency of all infrared light emitting diodes having a center wavelength in the reflection spectrum.

10: light emitting diode
100: substrate
200: broadband DBR
210: first DBR, 220: second DBR, 230; Third DBR, 240; First separating layer 250; 2nd separating layer
300: light emitting layer
310: lower limiting layer, 320: active layer, 330: upper limiting layer
400: Windows
510: lower electrode
520: upper electrode

Claims (19)

A first DBR in which a first high refractive index layer and a first low refractive index layer are repeatedly stacked;
A second DBR in which a second high refractive index layer and a second low refractive index layer are repeatedly stacked;
A third DBR in which a third high refractive index layer and a third low refractive index layer are repeatedly stacked;
A first spacing layer positioned between the first DBR and the second BDR; And
Broadband DBR including a second separation layer positioned between the second DBR and the third DBR. The method of claim 1,
Broadband DBR, characterized in that the separation layers have a thickness of 10 nm or more. The method of claim 1,
Broadband DBR, characterized in that the spacing layers have a thickness of 100 nm or more. The broadband DBR of claim 1, wherein the spacing layers are epitaxially grown epitaxially grown layers in DBR. The method of claim 1,
Broadband DBR, characterized in that the separating layers are light-transmitting. The broadband DBR of claim 1, wherein the spacing layer is GaInP or AlAs. The broadband DBR of claim 1, wherein the first DBR has a center wavelength in the range of 700 to 800 nm. The method of claim 7,
Wherein the DBR 1 is _{Al x Ga 1 - x InP /} Al 1 - x Ga x InP, x value is a broadband DBR, characterized in that the 0.9 ~ 1.0 is repeated lamination. The broadband DBR of claim 1, wherein the second DBR has a central wavelength in the range of 800 to 900 nm. The method of claim 9,
Wherein the DBR 2 is _{Al y Ga 1 - y As /} Al 1 - y Ga y can be made to the As, where y values broadband DBR, characterized in that 0.8 <y <0.95 The repeated stacking. The broadband DBR of claim 1, wherein the third DBR has a center wavelength in the range of 900 to 1000 nm. The method of claim 11,
3 wherein the DBR is _{Al y Ga 1 - y As /} Al 1 - y Ga y can be made to the As, where y values broadband DBR, characterized in that 0.8 <y <0.95 The repeated stacking. The method of claim 1,
Broadband DBR, characterized in that the first separation layer is GaInP. The method of claim 1,
The second separation layer is a broadband DBR, characterized in that AlAs. A first DBR in which a first high refractive index layer and a first low refractive index layer are repeatedly stacked;
A second DBR in which a second high refractive index layer and a second low refractive index layer are repeatedly stacked;
A third DBR in which a third high refractive index layer and a third low refractive index layer are repeatedly stacked;
A first spacing layer positioned between the first DBR and the second BDR; And
Optical device comprising a broadband DBR including a second separation layer positioned between the second DBR and the third DBR. The optical device of claim 15, wherein the first DBR, the second DBR, and the third DBR are infrared DBRs and include an active layer that emits infrared rays. The optical device according to claim 15 or 16, wherein the optical device is a light emitting diode or a laser diode. A first DBR in which a first high refractive index layer and a first low refractive index layer are repeatedly stacked;
A second DBR in which a second high refractive index layer and a second low refractive index layer are repeatedly stacked; And
Broadband DBR comprising a; a first separation layer positioned between the first DBR and the second BDR. Growing a first DBR in which a first high refractive index layer and a first low refractive index layer are repeatedly stacked;
Growing a separation layer on the first DBR; And
Growing a second DBR in which a second high refractive index layer and a second low refractive index layer are repeatedly stacked on the separating layer
Broadband DBR manufacturing method comprising a.

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