KR100679235B1 - Semiconductor light emitting device and manufacturing method thereof - Google Patents

Abstract

The present invention relates to a semiconductor light emitting device and a method of manufacturing the same, the method of manufacturing the semiconductor light emitting device comprises the steps of: forming a first distributed Brag Reflector (DBR) doped n-type on the substrate; Forming a lower clad layer on the first DBR; Forming a light emitting active layer on the lower clad layer; Forming a first upper clad layer on the light emitting active layer in a first growth temperature range; Forming a second upper clad layer in a second growth temperature range lower than the first temperature range; And delta doping on the second upper clad layer. Accordingly, the thickness of the cladding layer is epitaxially grown at a low growth temperature, and the growth temperature is increased to epitaxially grow the rest of the cladding layer, thereby improving efficiency of the light emitting device and improving temperature characteristics.

Description

Semiconductor Light Emitting Device and Fabrication Method The Same

1 is a schematic side cross-sectional view of an AlInP / AlGaInP / InGaP RCLED according to the prior art.

2 is a schematic side cross-sectional view of an AlInP / AlGaInP / InGaP RCLED in accordance with the present invention.

3 is a block diagram illustrating a manufacturing method of FIG. 2.

4 is an enlarged side sectional view enlarging the cavity (IV) region of FIG. 2.

Description of the main parts of the drawing

100, 200: RCLED 110, 210: Substrate

120, 220: first dispersed Bragg reflector 130, 230: lower clad layer

140, 240: light emitting active layer 150, 250: upper clad layer

160 and 260: second distributed Bragg reflector 170 and 270: first electrode

180, 280: second electrode 141, 241: first barrier layer

142 and 242: first quantum well layer 143 and 243: second barrier layer

144, 244: second quantum well layer 145, 245: third barrier layer

146, 246: third quantum well layer 147, 247: fourth barrier layer

251: upper first clad layer 252: upper second clad layer

253: upper third cladding layer 255: delta doping layer

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor light emitting device and a method of manufacturing the same. More specifically, a semiconductor light emitting device including a doped layer formed to form a part of a clad layer at a low temperature and preventing dopant diffusion on the surface thereof, and a fabrication thereof It is about a method.

Generally, light sources for optical communication in the 650 nm band used for plastic optical fiber (POF) communication include a vertical resonance surface emitting laser, a side emitting laser, and a high luminance light emitting diode (LED). Compared with semiconductor lasers, communication LEDs have good output linearity, no noise increase due to reflected light, long life, high reliability, and low price, but they have small light output, slow response speed, and large light emission angle. There is a disadvantage that the coupling efficiency with the optical fiber is poor. Therefore, the resonant cavitation light emitting diode (RCLED) in the 650 nm band has been in the spotlight as an optical transmission component used in a POF system, in which the disadvantages of a semiconductor laser and a light emitting diode are compensated for.

The RCLED provides a cavity area in a general light emitting diode structure, and like a vertical cavity surface emitting laser diode (VCSEL), a distributed Bragg reflector that can act as a mirror on both sides of the cavity. (DBR: Distributed Brag Reflector) is formed. The difference from the case of the vertical resonant surface light emitting laser diode is that in the case of the vertical resonant surface light emitting laser diode, the first DBR and the second are so that photons made in the active layer can obtain sufficient gain for lasing through the DBR. While the reflectance of the DBR is more than 99.5%, the RCLED has a slight difference depending on the purpose of manufacture, but the reflectance of one DBR is about 95%, and the reflectance of the other DBR is less than 10% to 50%. It is manufactured to have a reflectance of. In addition, the thickness of one layer used in the DBR is generally made to be 1/4 of the emission wavelength.

Hereinafter, the RCLED according to the prior art will be described with reference to the drawings.

1 is a partial cross-sectional view of an RCLED having an AlInP / AlGaInP / InGaP epi structure according to the prior art. Referring to FIG. 1, an AlInP / AlGaInP / InGaP RCLED 100 includes a first GaNs substrate 110 having an n-type and AlxGa1-xAs / AlyGa1-yAs doped with n-type on the substrate 110. DBR 120, lower cladding layer 130 formed on first DBR 120, light emitting active layer 140 formed on lower clad layer 130, and an upper portion formed on light emitting active layer 140. The cladding layer 150 and the second DBR 160 are formed on the upper cladding layer 150. Electrodes 170 and 180 are formed below the substrate 110 and above the second DBR 160, respectively.

Typically, the upper and lower cladding layers 130 and 150 and the light emitting active layer 140 are referred to as a cavity area. The cavity region is formed to have a thickness corresponding to an integral multiple of the half wavelength. The cladding layers 130 and 150 are made of Al (Ga) InP, and the light emitting active layer 140 includes quantum well layers 142, 144, and 146 and barrier layers 141, 143, 145, and 147. The second DBR 160 is composed of p-type doped Al x Ga 1-x As / AlyGa 1-y As. In FIG. 1, the number of AlxGa1-xAs / AlyGa1-yAs pairs used in the first DBR 120 and the second DBR 160 and the composition of each layer may be slightly different depending on the use of the RCLED.

Referring to the components disclosed in Figure 1 in more detail, the bandgap of the material used in the DBR composition of Al than Al0.45Ga0.55As having a bandgap larger than the light emission wavelength so that it can not absorb the light emission wavelength produced in the active layer Use this large material. If the DBR is composed of Al0.95Ga0.05As / Al0.5Ga0.5As and the light is emitted to the surface, the AlxGa1-xAs / AlyGa1-yAs is approximately 30 to 40 in order to have a high reflectance for the first DBR. In the case of the second DBR in pairs, when 5 to 10 pairs are stacked, the emitted light may be emitted toward the surface opposite to the substrate. The AlGaInP-based compound semiconductor can be lattice matched to a GaAs substrate by adjusting the composition to approximately (AlxGa1-x) 0.51In0.49P.

Accordingly, the compound composition and thin film thickness of the quantum well layer and the barrier layer used to produce the 650 nm wavelength is 8 nm and the barrier layers 141, 143, In0.49Ga0.51P for the quantum well layer 142, 144, and 146. In the case of 145 and 147, (Al 0.5 Ga 0.5) 0.51 In 0.49 P may be formed by stacking (9 nm). In addition, since the cladding layer 150 may select a material having a larger aluminum (Al) composition than the barrier layer in order to have a larger bandgap than the barrier layers 141, 143, 145, and 147, the AlInP in the above embodiment may be selected. It formed into a cladding layer. At this time, when the thickness of the cavity including the active layer 140 and the cladding layers 130 and 150 is epitaxially grown to one wavelength, the thickness of AlInP is approximately 56 nm.

However, in the case of the RCLED structure fabricated according to the above-described prior art, although the carrier electrons must be confined to the active layer quantum well layer, the band-offset of the conduction band becomes smaller as the temperature increases. As a result, carrier leakage increases in the direction of the second DBR doped in the p-type without being constrained to the quantum well layer, thereby causing a problem that the RCLED significantly degrades optical characteristics at high temperature. In addition, it is disclosed in Materials Seience and Engineering, B74 165 (2000) of vilokinen et al. That RC growth is not easy and there is a technical limitation that high temperature driving is limited.

In other words, the fundamental reason of the above technical limitation is that in the heterojunction of InGaP and AlGaInP used as the active layer material of 650nm RCLED, the band offset of the conduction band is smaller than the band offset of the valence band. As the effective mass of is small, the movement is easy, whereas the effective mass of the hole is so large that the movement is not easy, so the behavior of the carriers is severely affected by the temperature as the temperature increases, There is a disadvantage that the carrier distribution becomes non-uniform, which results in degradation of the overall optical device characteristics.

The present invention has been devised to solve the above problems, and an object of the present invention is to provide a semiconductor light emitting device having excellent photoelectric conversion efficiency and a low temperature influence on optical characteristics, and a method of manufacturing the same.

It is also an object of the present invention to provide a semiconductor light emitting device and a method for manufacturing the same, which can prevent the leakage of carriers caused by the temperature increase by forming a potential barrier using delta doping.

According to an aspect of the present invention for achieving the above object, the present invention provides a method of manufacturing a semiconductor light emitting device comprising the steps of: forming a first distributed Brag Reflector (DBR) doped n-type on the substrate; Forming a lower clad layer on the first DBR; Forming a light emitting active layer on the lower clad layer; Forming a first upper clad layer on the light emitting active layer in a first growth temperature range; Forming a second upper clad layer in a second growth temperature range lower than the first growth temperature range; And delta doping on the second upper clad layer.

Preferably, after performing the delta doping, further comprising forming a third upper clad layer on the second upper clad layer in the second growth temperature range. In the delta doping step, doping is performed using a p-type dopant, and the p-type dopant uses Zn, Mg, Be, C, and the like.

The thickness of the second upper cladding layer and the third upper cladding layer is controlled by the growth temperature range or the diffusion distance according to the dopant or the diffusion temperature according to the growth temperature range and the dopant. The thickness of the second upper clad layer is formed in a thickness range of 10 to 50nm. The thickness of the third upper clad layer is selected from the thickness range of the second upper clad layer and is formed to be the same as or different from the thickness of the second upper clad layer. The second growth temperature range for forming the second upper clad layer and the third upper clad layer is a temperature range lower by 50 to 100 ° C. than the first growth temperature range. The substrate is made of GaAs, Si, ZnO, Ge or InP.

According to another aspect of the present invention for achieving the object, the present semiconductor light emitting device comprises: a first DBR formed on a substrate; A lower clad layer formed on the first DBR; A light emitting active layer formed on the lower clad layer; A first upper clad layer formed on the light emitting active layer; A second upper clad layer formed on the first upper clad layer; A delta doped layer formed on the second upper clad layer; And a third upper clad layer formed on the delta doped layer. Preferably, the delta doped layer uses a p-type dopant.

Hereinafter, with reference to the accompanying drawings will be described the present invention in more detail.

Figure 2 is a schematic side cross-sectional view of the AlInP / AlGaInP / InGaP RCLED according to the present invention, Figure 3 is a block diagram showing the manufacturing method of FIG. Figure 2 is a cross-sectional view of the RCLED proposed to have a high optical characteristics at a high temperature proposed in the present invention showing the epi structure of the cavity area in more detail. Referring to FIG. 2, the AlInP / AlGaInP / InGaP RCLED 200 includes a substrate 210, a first distributed Bragg reflector layer 220, a lower clad layer 230, a light emitting active layer 240, and an upper clad layer 250. And a second distributed Bragg reflector layer 260, and first and second electrodes 270 and 280.

2 and 3, in order to manufacture the RCLED 200 according to the present invention, first, a substrate 210 is prepared (S301). The substrate 210 may be made of GaAs, Si, ZnO, Ge, or InP. In this embodiment, an n-type GaAs substrate is used. Next, a first distributed brag reflector (DBR) 220 is formed on the substrate 210 (S302). The first DBR 220 is composed of n-type doped Al x Ga 1-x As / AlyGa 1-y As.

The lower clad layer 230 is formed on the first DBR 220 (S303), and the light emitting active layer 240 is formed on the lower clad layer 130 (S304). The light emitting active layer 240 includes quantum well layers 242, 244 and 246 and barrier layers 241, 243, 245 and 247. An upper cladding layer 250 is formed on the light emitting active layer 240. In the present exemplary embodiment, the upper cladding layer 250 includes a first upper cladding layer (not shown), a second upper cladding layer (not shown), and a third cladding layer. Upper clad layers (not shown) are sequentially formed (S305, S306, S308). Here, a doped delta doping layer (not shown) is formed between the second upper clad layer and the third upper clad layer (S307). A second distributed brag reflector (DBR) layer 260 is formed on the upper cladding layer 250 (S309), and the second DBR 260 is p-type doped AlxGa1-xAs / AlyGa1-yAs. It consists of. In the present embodiment, the lower and upper cladding layers 230 and 250 are made of Al (Ga) InP. Although not shown in FIG. 3, the first electrode 270 is formed on the bottom surface of the substrate 210, and the second electrode 280 is formed on the second DBR 260. The first electrode 270 may be formed at the last step of forming all other layers on the substrate 210 or at the next step of preparing the substrate 210.

A region including the upper and lower clad layers 230 and 250 and the light emitting active layer 240 is called a cavity region IV. In general, the cavity region IV is formed to have a thickness corresponding to an integral multiple of the half wavelength. Meanwhile, in FIG. 2, the number of AlxGa1-xAs / AlyGa1-yAs pairs used in the first DBR 220 and the second DBR 260 and the composition of each layer may be slightly different depending on the use of the RCLED.

More specifically, referring to FIG. 4, which is an enlarged side cross-sectional view of the enlarged cavity (IV) region of FIG. 2, the epitaxial structure of the preferred cavity region (IV) has an undoped AlInP lower cladding having a thickness of 56 nm at a temperature of 650 ° C. FIG. (Al0.5Ga0.5) 0.51In0.49P barrier layer 241, 243, 245, 247 epitaxially grown 9nm thick on layer 230 and In0.49Ga0.51P quantum well layer 242 grown 8nm thick , 244 and 246 are sequentially stacked to form the light emitting active layer 240.

After the first upper cladding layer 251 of undoped AlInP of about 40 nm is epitaxially grown on the light emitting active layer 240 in the first temperature range (for example, 650 ° C.), the second temperature range (in the first temperature range). The second upper clad layer 252 is formed by stacking an undoped AlInP layer with a thickness of 8 nm in a temperature range lowered by approximately 50 ° C.). Next, delta doping is performed on the second upper clad layer 252. When delta doping is performed, p-type dopants such as Zn, Mg, Be, and C are used. In the present embodiment, the delta doped layer 255 is formed using Zn. Formation of the delta doped layer 255 will be described in more detail below. A third upper clad layer 253 is formed on the delta doped layer 255, and the third upper clad layer 253 is formed of an AlInP layer undoped to a thickness of 8 nm, similar to the second upper clad layer 252.

As a result, the total thickness of the first upper clad layer 251 grown in the first temperature range (650 ° C.) and the second and third upper clad layers 252 and 253 epitaxially grown in the lower temperature range (600 ° C.) is Like the lower clad layer 230, it is approximately 56 nm thick. Here, the thicknesses of the second and third upper clad layers 242 and 253 which are grown at low temperature may be determined in a range such that the influence of diffusion of the delta-doped p-type dopant does not affect the active layer in consideration of the growth temperature. have. If the growth temperature of the second temperature range, that is, the second and third upper cladding layers 252 and 253 is lower than 600 ° C., the thickness of the cladding layer grown at low temperature may be made thinner than the thickness. Meanwhile, the first dispersed Bragg reflector layer 220, the lower clad layer 230, and the light emitting active layer 240 may be grown in the first temperature range.

Hereinafter, operation S307 of FIG. 3, which forms the delta doped layer 255, will be described in detail.

First, epitaxially grown a first upper cladding layer 251 of AlInP to a thickness of 40 nm at a growth temperature in the first temperature range (650 ° C.), and then emit Al and In sources TMAl and TMIn, which are Group III elements. vent so as not to enter the chamber, and then allow only PH3 source and carrier gas, H2, to enter the chamber and lower the temperature to 600 ° C. When the temperature is stabilized, the TMAl and TMIn sources are introduced into the chamber again to epitaxially grow the second upper clad layer 252 of AlInP having a thickness of 8 nm.

Next, the TMAl and TMIn sources are discharged out of the chamber to stop growth of the second upper clad layer 252 (AlInP) for 10 seconds, and then the DEZn source is introduced into the chamber for 30 to 60 seconds together with H2 and PH3. To form a Zn delta doped layer 255. Next, the third upper clad layer (AlInP layer) 253 is grown by 8 nm while the TMAl and TMIn sources are immediately introduced while the inflow of the DEZn source is stopped. Then, the source of the group III element is cut off again, and the temperature is stabilized by raising the growth temperature to only 650 ° C. in the group V source gas and H 2 atmosphere, and then the second DBR layer 260 of AlGaAs / AlGaAs is grown.

In general, p-type dopants are known to be easily diffused, and when the p-type dopants are introduced into the active layer, they can act as non-radiative recombination centers, thereby reducing light efficiency. As is known, there is a need to minimize its diffusion during delta doping. Therefore, when delta doping is performed at a lower temperature than the growth temperature when growing another layer as in the embodiment of the present invention, the dopant may be doped only in a very narrow region with a very short diffusion distance.

According to the foregoing, after the epitaxial growth of a predetermined thickness of the clad layer at a low growth temperature to prevent the diffusion of the Zn dopant, to form a potential barrier layer and delta doping using Zn for smooth supply of holes, When the remaining cladding layer is grown at a low growth temperature, the cladding layer including the delta doped layer becomes a potential barrier to electrons leaking into the cladding layer without being confined to the quantum well layer as the temperature increases. By increasing the binding force of the carrier, it is possible to provide a semiconductor light emitting device having excellent photoelectric conversion efficiency even at a high temperature.

The Zn delta doping layer implemented in the method of manufacturing a semiconductor light emitting device of the present invention is not limited to the quantum well layer when the temperature of the fabricated RCLED increases, and it is as if the electrons are overflowed to the second DBR region. It can act as a potential barrier to provide an effect of increasing the binding force of the electron to the active layer, and furthermore, since the optical properties are not sensitive to temperature changes, it is possible to manufacture a semiconductor light emitting device excellent in photoelectric conversion efficiency. In addition, when delta doping is used, a semiconductor light emitting device having high brightness and high luminous efficiency can be provided by combining an n-type contact layer having a low resistivity and a current spreading induction layer having a high resistivity and uniformly injecting current into the active layer. .

Claims (11)

Forming a first Distributed Brag Reflector (DBR) doped n-type on the substrate; Forming a lower clad layer on the first DBR; Forming a light emitting active layer on the lower clad layer; Forming a first upper clad layer on the light emitting active layer in a first growth temperature range; Forming a second upper clad layer in a second growth temperature range lower than the first temperature range; And Delta doping on the second upper clad layer Method for manufacturing a semiconductor light emitting device comprising a. The method of claim 1, And forming a third upper clad layer on the second upper clad layer in the second growth temperature range after the delta doping. The method of claim 2, In the delta doping step, a semiconductor light emitting device manufacturing method using a p-type dopant. The method of claim 3, The p-type dopant is selected from Zn, Mg, Be, C and doped semiconductor light emitting device manufacturing method. The method of claim 3, The thickness of the second upper clad layer and the third upper clad layer is A method of manufacturing a semiconductor light emitting device controlled by the growth temperature range or the diffusion distance according to the dopant or the growth temperature range and the diffusion distance according to the dopant. The method of claim 5, The thickness of the second upper clad layer is a semiconductor light emitting device manufacturing method formed in a thickness range of 10 ~ 50nm. The method of claim 6, The thickness of the third upper clad layer is selected from the thickness range of the second upper clad layer, the semiconductor light emitting device manufacturing method of the same or different from the thickness of the second upper clad layer. The method according to claim 1 or 2, The second growth temperature range for forming the second upper clad layer and the third upper clad layer is a temperature range of 50 ~ 100 ℃ lower than the first growth temperature range of the semiconductor light emitting device manufacturing method. The method of claim 1, The substrate is a method of manufacturing a semiconductor light emitting device consisting of GaAs, Si, ZnO, Ge, or InP. A first DBR formed on the substrate; A lower clad layer formed on the first DBR; A light emitting active layer formed on the lower clad layer; A first upper clad layer formed on the light emitting active layer; A second upper clad layer formed on the first upper clad layer; A delta doped layer formed on the second upper clad layer; And A third upper clad layer formed on the delta doped layer Semiconductor light emitting device comprising a. The method of claim 10, The delta doped layer is a semiconductor light emitting device doped using a p- type dopant.

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