KR20130017112A - High efficiency semiconductor photo device structure having electron tunneling barrier layer and manufacturing method thereof - Google Patents

Abstract

PURPOSE: A high efficiency semiconductor photo device structure having an electron tunneling barrier layer and a manufacturing method thereof are provided to improve optical extraction efficiency by inserting an electron tunneling barrier between a N-type GaN layer and a multi quantum well. CONSTITUTION: An electron tunneling barrier layer(232) is formed on an N-type nitride semiconductor layer(AlxInyGa1-x-yNs (0≤x≤1, 0≤y≤1, 0≤x+y≤1)). A multiple quantum well(233) is formed on the ETB layer as an active layer. A P-type nitride semiconductor layer(235) is formed on the multiple quantum well. The electron tunneling barrier layer improves the recombination of holes which are injected from a P-type nitride semiconductor layer into the multiple quantum well. [Reference numerals] (210) Substrate; (220) Template layer; (230) LED layer; (234) Removable

Description

High Efficiency Semiconductor Photo Device Structure having Electron Tunneling Barrier Layer and Manufacturing Method

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a structure of a semiconductor optical device such as a light emitting diode (LED) and a manufacturing method thereof. In particular, an ETB layer having an energy band gap (Eg) larger than that of GaN is used. Inserted between the N-type GaN layer and the active layer MQW layer (Multi Quantum Well layer) to match the ratio of electrons and holes in the MQW layer due to the tunneling effect and reduce the carrier overflow phenomenon High-quality semiconductor optical device structure and its manufacture that can improve the internal quantum efficiency and light extraction efficiency without using the Electron Blocking Layer (Electron Blocking Layer) and increase the efficiency by increasing the hole injection because the EBL layer is not required It is about a method.

Recently, group III-V nitride semiconductors such as GaN have been spotlighted as core materials of semiconductor optical devices such as light emitting diodes (LEDs), laser diodes (LDs), and solar cells due to their excellent physical and chemical properties. Ⅲ-Ⅴ nitride semiconductor is made of a semiconductor material having a composition formula of the conventional _{Al x In y Ga 1 -x- y} N (0≤x≤1, 0≤y≤1, 0≤x + y≤1). The nitride semiconductor optical device is applied as a light source of various products such as a backlight of a mobile phone, a keypad, an electronic signboard, an illumination device, and the like. In particular, as digital products evolve, there is an increasing demand for nitride semiconductor optical devices having greater brightness and higher reliability.

1 illustrates a structure of a conventional light emitting diode 100. Referring to FIG. 1, a conventional light emitting diode 100 forms a template layer 120 serving as a buffer on a substrate 110 such as sapphire and has an LED layer 130 thereon. The LED layer 130 includes an MQW layer 132 and an EBL layer 133, which are active layers, between the N-type GaN layer 131 and the P-type GaN layer 134 connected to the electrodes 141/142. The MQW layer 132 is generally a quantum well layer that repeats the InGaN / GaN layer several times so that electrons can be confined to the well and recombine.

As shown in the energy band structure of FIG. 2, the EBL layer 133 has a larger energy band gap than the InGaN / GaN layer, and the P-type GaN layer 134 is formed through tunneling or leakage paths according to defects present therein. Although some electrons are leaked out), most electrons are blocked from flowing to the P-type GaN layer 134, thereby increasing the recombination rate of electron-holes, thereby increasing light extraction efficiency.

However, in the conventional light emitting diode structure as described above, there is a problem of increasing the operating voltage by increasing the forward voltage Vf due to the large band gap difference between the GaN layer of the EBL layer 133 and the MQW layer 132. In addition, hole injection from the P-type GaN layer 134 to the MQW layer 132 is also not smooth, resulting in a low electron-hole recombination rate, resulting in low light extraction efficiency, resulting in low total emission intensity. Therefore, it is proposed a semiconductor optical device structure such as a light emitting diode that can improve the light emission intensity.

Accordingly, the present invention is to solve the above-described problems, the object of the present invention, for applying to semiconductor optical devices such as light emitting diodes (LED), laser diodes (LD), solar cells, energy bandgap (Eg) than GaN A large ETB layer (Electron Tunneling Barrier) is inserted between the N-type GaN layer and the active MQW layer (Multi Quantum Well layer) to form electrons and holes in the MQW layer due to the tunneling effect. By adjusting the ratio of holes and reducing carrier flooding, it improves the internal quantum efficiency and light extraction efficiency without using the existing EBL layer (Electron Blocking Layer). It is to provide a high-quality semiconductor optical device structure and its manufacturing method that can be increased to further increase the efficiency.

First, to summarize the features of the present invention, a method for manufacturing a semiconductor optical device such as a light emitting diode (LED), a laser diode (LD), a solar cell according to an aspect of the present invention for achieving the above object of the present invention, N Electron Tunneling Barrier with Al _x In _y Ga _{1-x- y} N (0≤x≤1, 0≤y≤1, 0≤x + y≤1) on the nitride semiconductor layer A layer, a multi-quantum well layer as an active layer on the ETB layer, and a P-type nitride semiconductor layer formed on the multi-quantum well layer, wherein the ETB layer has an energy band gap greater than that of the N-type nitride semiconductor layer. By enlarging the electrons tunneling the ETB layer from the N-type nitride semiconductor layer to the multi-quantum well layer, the recombination rate between the electrons and the holes injected from the P-type nitride semiconductor layer into the multi-quantum well layer is increased. It is special to let It shall be.

The thickness of the ETB layer may be 0.1 ~ 3.0 nm.

The ETB layer includes an Al _x In _{1 - x} N layer (0 <x <1), where x is greater than or equal to 0.6 and less than one.

The ETB layer may be doped with an N-type dopant of at least one of Si, O, S, C, Ge, Zn, Cd, and Mg.

A sapphire, GaN, SiC, AlN, ZnO, LiAlO ₂ , or LiGaO ₂ substrate may be used as a substrate for forming the semiconductor optical device, and a polar and non-polar substrate may be used as a substrate for forming the semiconductor optical device. ) Or a substrate having a crystal plane on which a semi-polar nitride semiconductor is grown can be used.

In addition, a semiconductor optical device according to another aspect of the present invention, an N-type nitride semiconductor layer; The N-type nitride semiconductor layer ETB (Electron Tunneling Barrier) formed of _{Al x In y Ga 1 -x- y} N (0≤x≤1, 0≤y≤1, 0≤x + y≤1) above the floor; A multiple quantum well layer formed as an active layer on the ETB layer; And a P-type nitride semiconductor layer formed on the multi-quantum well layer, wherein the ETB layer tunnels the ETB layer from the N-type nitride semiconductor layer by having an energy band gap larger than that of the N-type nitride semiconductor layer. Constrained to the multi-quantum well layer, characterized in that for increasing the recombination rate between the electron and the hole injected into the multi-quantum well layer from the P-type nitride semiconductor layer.

The semiconductor optical device includes a light emitting diode, a laser diode, a photodetecting device, or a solar cell.

According to the semiconductor optical device structure and manufacturing method thereof according to the present invention, electrons in the MQW layer due to the tunneling effect by inserting an ETB layer having a larger energy band gap (Eg) than GaN between the N-type GaN layer and the active MQW layer By adjusting the ratio of holes and holes and reducing the carrier overflow phenomenon, the internal quantum efficiency and light extraction efficiency can be improved without using the existing EBL layer. It can be increased, and thus can be applied to light emitting diodes (LEDs), laser diodes (LDs), solar cells, and the like, which require high emission intensity, so as to be manufactured at high quality.

1 shows the structure of a conventional light emitting diode.
FIG. 2 is an energy band diagram of the structure of FIG. 1. FIG.
3 shows a structure of a light emitting diode according to an embodiment of the present invention.
4 is an energy band diagram for FIG. 3.
FIG. 5A is a graph for explaining carrier concentration in an MQW layer of a conventional (FIG. 1) structure. FIG.
Fig. 5B is a graph for explaining carrier concentration in the MQW layer of the structure of the present invention (Fig. 3).
6A is a graph for explaining the recombination rate in the MQW layer of the existing structure.
6B is a graph for explaining the recombination rate in the MQW layer of the structure of the present invention.
7 is a graph for comparing the internal quantum efficiency (IQE) and the forward voltage (Vf) of the existing structure and the structure of the present invention.
8 is a graph for comparing the total emission intensity of the existing structure and the structure of the present invention.
9 is a graph for comparing the emission intensity of the existing structure and the present invention structure at the maximum doping concentration of the P-type GaN layer.
10 is a graph for comparing the emission intensity of the existing structure and the present invention structure in each well layer of the MQW layer.
11 is a graph for comparing the internal quantum efficiency droop characteristics of the existing structure and the present invention structure.
12 is a graph for comparing the light emission intensity of the present invention structure with respect to the Al composition change and the light emission intensity of the existing structure.
Fig. 13 is a graph showing the light emission intensity of the structure of the present invention with respect to the thickness change of the ETB layer.
14 is a graph showing the emission intensity of the structure of the present invention with respect to the N-type doping concentration change in the ETB layer.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout.

3 shows a structure of a light emitting diode 200 according to an embodiment of the present invention. Hereinafter, the energy band diagram of FIG. 4 will be described. The energy band diagram of FIG. 4 is shown in a rough straight line with respect to the structure of FIG. 3, and in actual manufacturing, bending of conduction bands and valence bands of energy bands of each layer due to polarity may occur due to polarity when growing on the C-plane. And also includes polar as well as nonpolar, semipolar LED manufacturing.

Referring to FIG. 3, a light emitting diode 200 according to an embodiment of the present invention includes a substrate 210, a template layer 220 formed thereon, and a light emitting diode (LED) layer 230. do.

Hereinafter, the structure of the light emitting diode 200 in which the light emitting diode (LED) layer 230 is formed on the template layer 220 as shown in FIG. 3 will be described. However, the structure of the light emitting diode (LED) layer 230 is a laser diode. It can be found that the present invention can be similarly applied to various semiconductor optical devices such as photodetection devices or solar cells.

In FIG. 3, the substrate 210 may be made of sapphire, and in some cases, the substrate 210 may not include a substrate made of various materials such as GaN, SiC, AlN, ZnO, LiAlO ₂ , LiGaO _2, and the like. In addition, the crystal plane (eg, sapphire crystal plane) of the substrate 210 may have a C-plane (eg, (0001) plane) and a non-polar (non-polar) surface where a nitride semiconductor such as polar GaN may be grown thereon. A-plane (e.g., (11-20) plane), M-plane (e.g., (10-10), on which nitride semiconductors such as -polar) or semi-polar GaN can be grown Plane), or R-plane (eg, (1-102) plane) and the like.

The template layer 220 is a light emitting diode (LED) as a buffer layer for forming a layer _{(230) Al x In y Ga} 1 -x- y N (0≤x≤1, 0≤y≤1, 0≤x + y 1) or a GaN layer.

The LED layer 230 includes an ETB layer (electron tunneling barrier layer) 232 and an active layer between the N-type GaN layer 231 and the P-type GaN layer 235 connected to the electrodes 241/242. And an MQW layer (multi quantum well layer) 233, and in some cases, an existing EBL layer (Electron Blocking Layer) between the MQW layer (multi quantum well layer) 233 and the P-type GaN layer 235. Electron blocking layer) 234 may be included. The EBL layer 234 has a larger energy band gap than the GaN layer, which is a barrier layer of the MQW layer 233, and blocks electrons entering the MQW layer 233 from flowing into the P-type GaN layer 235. By increasing the recombination rate of electrons and holes in the MQW layer 233 can increase the light extraction efficiency.

In the present invention, an ETB layer 232 having a larger energy band gap (Eg) than GaN of the N-type GaN layer 231 is inserted between the N-type GaN layer 231 and the MQW layer 233 as an active layer, thereby providing an ETB layer ( By adjusting the ratio of electrons and holes in the MQW layer 233 due to the tunneling effect of 232 and reducing the carrier overflow phenomenon, the internal quantum efficiency and light extraction efficiency are improved without using the EBL layer 234 as described above. Since the EBL layer 234 is not required, the hole injection from the P-type GaN layer 235 to the MQW layer 233 is increased to further increase the efficiency, and thus a light emitting diode requiring high emission intensity ( LED), laser diode (LD), solar cells and the like to be manufactured with high quality.

In FIG. 3, an N-type GaN layer 231, which is an N-type nitride semiconductor layer, may be formed by growing a GaN layer doped with an N-type dopant such as Si to a thickness of about 2 micrometers.

N-type GaN layer (231) ETB layer 232 is formed in the forming the _{Al x In y Ga 1 -x- y} N (0≤x≤1, 0≤y≤1, 0≤x + y≤1) The composition ratio of Al may be selected so that an energy band gap is larger than that of the N-type GaN layer 231. For example, as described below, the thickness of the ETB layer 232 may be formed in a range of 0.1 to 3.0 nm, and in particular, an Al _x In _{1 - x} N layer (x of 0 <x <1, where x is greater than or equal to 0.6 and less than 1). It can be made of). In addition, the ETB layer 232 may be doped with at least one or more N-type dopants of Si, O, S, C, Ge, Zn, Cd, and Mg.

The MQW layer 233 includes quantum well layers in which a quantum well layer (InGaN layer) W and a barrier layer (GaN layer) B are repeated a plurality of times (for example, five times), and the electrode 241 / When applying a voltage higher than the forward voltage Vf to 242, the thin ETB layer 232 is tunneled to allow the incoming electrons to restrain and recombine the well layer W. The quantum well layer W may be formed to a thickness of about 2.5 nanometers, and the barrier layer B may be formed to a thickness of about 5 to 7.5 nanometers.

The InGaN quantum well layer and the GaN barrier layer of the MQW layer 233 may be non-doped layers, but may be doped at a dopant concentration of about 1 * 10 ¹⁶ to 1 * 10 ¹⁷ (/ cm3), and Si may be used as a dopant. At least one or more of O, S, C, Ge, Zn, Cd, and Mg may be used. The InGaN quantum well layer is composed of a composition formula such as In _x Ga _{1 - x} N (0 <x <1), and x = 0.15 to 0.17 is appropriate, and the In component ratio may be different in some cases.

Meanwhile, the P-type GaN layer 235, which is a P-type nitride semiconductor layer formed on the MQW layer 233 or the EBL layer 234, is a GaN layer doped with P-type dopants such as Mg at about 1 * 10 ¹⁸ (/ cm3). It can be formed so that the thickness is grown to about 120 nanometers. In actual manufacturing, the concentration of the P-type GaN layer 235 may be 1 * 10 ¹⁸ (/ cm3) or less.

In the semiconductor optical device structure of the present invention, the electrons of the N-type GaN layer 231 tunnels the ETB layer 232 when the voltage of the forward voltage Vf or more is applied to the electrodes 241/242 to the MQW layer 233. Electrons confined by the MQW layer 233 are recombined with holes injected from the P-type GaN layer 235 into the MQW layer 233. At this time, the hole injection is prevented to some extent by the EBL layer 234, but the removal of the EBL layer 234 balances the amount of electrons and holes injected into the MQW layer 233. Accordingly, P in the MQW layer 233 is adjusted. Carriers (electrons) that overflow to the type GaN layer 235 can be reduced, thereby increasing the electron-hole recombination rate in the MQW layer 233 to increase the internal quantum efficiency and light extraction efficiency.

The results of the experiment (simulation) on the semiconductor optical device structure of the present invention as described above are summarized as follows.

FIG. 5A is a graph for explaining carrier concentration in an MQW layer of a conventional (FIG. 1) structure. FIG. 5B is a graph for explaining carrier concentration in the MQW layer 233 of the present invention (FIG. 3) structure. 5A and 5B, the recombination is maximized at the point where the electron and hole concentration curves of each well layer W meet, and the structure of the present invention is compared to the existing structure of FIG. 5A under the same current density condition. It was confirmed that the point where the concentration curve of electrons and holes in W) appeared to be high, and thus, recombination was more actively performed in the MQW layer 233 of the present invention than the existing structure.

6A is a graph for explaining the recombination rate in the MQW layer of the existing structure. 6B is a graph for explaining the recombination rate in the MQW layer of the structure of the present invention. Herein, in the same current density condition, the structure of the present invention is larger in the light emitting recombination ratio in each well layer W and the non-radiative recombination ratio is small in comparison with the existing structure of FIG. 6A. As a result, it was confirmed that the recombination rate is higher, so that the recombination in the MQW layer 233 of the present invention is more active than the existing structure.

7 is a graph for comparing the internal quantum efficiency (IQE) and the forward voltage (Vf) of the existing structure and the structure of the present invention. Here, by inserting the ETB layer 232 like the present invention instead of the existing EBL layer under the same current density condition, the internal quantum efficiency (IQE) is increased by about 2 times compared to the existing structure, and the forward voltage (Vf) is almost more than that of the existing structure. It was confirmed that no increase was seen. For reference, the internal quantum efficiency IQE corresponds to a ratio of recombination rate that contributes to light emission with respect to the total recombination rate in the MQW layer 233.

8 is a graph for comparing the total emission intensity of the existing structure and the structure of the present invention. In the above experimental conditions, as shown in FIG. 8, the total emission intensity generated in the entire MQW layer 233 was confirmed to be about 2 times higher at the emission wavelength than the existing structure.

9 is a graph for comparing the emission intensity of the existing structure and the present invention structure at the maximum doping concentration of the P-type GaN layer. In consideration of the actual manufacturing environment of the P-type GaN layer 235 as shown in FIG. 9, the concentration of the P-type dopant of the P-type GaN layer 235 is 5 * 10 ¹⁷ (/ cm3). In the results of the case of the maximum doping concentration of 1 * 10 ¹⁸ (/ cm3) of the P-type GaN layer, the light emission intensity was found to be slightly smaller than that of the conventional structure.

10 is a graph for comparing the emission intensity of the existing structure and the present invention structure in each well layer of the MQW layer. Even when comparing the well layers of the MQW layer as shown in FIG. 10, the structure of the present invention shows higher emission intensity in each well layer than the conventional structure, and particularly in the existing structure in the last well layer toward the P-type GaN layer 235. Although the light emission intensity decreases, the structure of the present invention, on the contrary, indicates that the light emission intensity increases. It is confirmed that the holes injected from the P-type GaN layer 235 are recombined as soon as they are injected into the MQW layer. Accordingly, the phenomenon that the electrons of the MQW layer overflow the P-type GaN layer 235 is also significantly improved. It was. However, this is merely an example, and depending on the manufacturing process, holes injected from the P-type GaN layer 235 may be recombined as soon as they are injected into the MQW layer. In some cases, the holes are dispersed in each well layer of the MQW layer. It may be recombined, so that the distribution of luminescence intensity of each well layer may be slightly different from that in FIG.

11 is a graph for comparing the internal quantum efficiency droop characteristics of the existing structure and the present invention structure. As shown in FIG. 11, when the current density is changed, it is confirmed that the internal structure ETB of the present invention exhibits a higher internal quantum efficiency IQE compared to the existing structure EBL.

12 is a graph for comparing the light emission intensity of the present invention structure with respect to the Al composition change and the light emission intensity of the existing structure. As shown in FIG. 12, when the ETB layer 232 is formed of an Al _x In _{1 - x} N layer (where x is less than 0.6 or less than 1 in 0 <x <1), the structure (ETB) of the present invention is generally existing. It can be seen that the emission intensity is high compared to the structure (EBL). Herein, even when the composition ratio of Al increases, the band gap of the ETB increases but the emission intensity is high, which indicates that the amount of electrons and holes passing through the ETB layer 232 rather than the hole blocking role of the ETB layer 232 increases. It seems to match ratio.

13 is a graph showing the luminescence intensity of the structure of the present invention with respect to the thickness change of the ETB layer 232. As a result of experiments by changing the thickness of the ETB layer 232 to 1 to 3nm as shown in FIG. 13, the light emission intensity decreases slightly as the thickness increases, so that the thickness of the ETB layer 232 is preferably 0.1 to 3.0 nm. It was confirmed.

14 is a graph showing the luminescence intensity of the structure of the present invention with respect to the N-type doping concentration change in the ETB layer 232. Of _{Al x In y Ga 1 -x- y} N (0≤x≤1, 0≤y≤1, 0≤x + y≤1) , or Al _x In _{1 -x} N layer (0 <x <1 x is ETB layer 232 of the present invention, which may be formed of 0.6 or more and less than 1), may be doped with at least one or more N-type dopants of silver Si, O, S, C, Ge, Zn, Cd, and Mg, wherein Even though the doping amount of the N-type dopant is changed to 1 * 10 ¹⁶ to 1 * 10 ¹⁹ (/ cm3) as shown in FIG. 14, the emission intensity tends to decrease to a small amount, but the ETB layer 232 is an N-type dopant because there is no significant effect. It has been found that it can be doped with.

As described above, in the structure of the light emitting diode or semiconductor optical device 200 of the present invention, the ETB layer 232 having an energy band gap Eg larger than that of GaN of the N-type GaN layer 231 is formed by the N-type GaN layer 231. Inserted between the active layer MQW layer 233, to balance the electrons and holes in the MQW layer 233 due to the tunneling effect of the ETB layer 232 and to reduce the carrier overflow to reduce the above EBL layer ( Internal quantum efficiency and light extraction efficiency can be improved without using 234, and since the EBL layer 234 is not required, hole injection from the P-type GaN layer 235 to the MQW layer 233 is increased to further increase efficiency. It can be increased, and thus can be applied to light emitting diodes (LEDs), laser diodes (LDs), solar cells, and the like, which require high emission intensity, so as to be manufactured at high quality.

As described above, the present invention has been described by way of limited embodiments and drawings, but the present invention is not limited to the above embodiments, and those skilled in the art to which the present invention pertains various modifications and variations from such descriptions. This is possible. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined by the equivalents of the claims, as well as the claims.

231: N-type nitride semiconductor layer
232: ETB: electron tunneling barrier layer
233: multiple quantum well layer
234: EBL: electron blocking layer
235 P-type nitride semiconductor layer
241, 242: electrode

Claims (8)

An ETB (Electron Tunneling Barrier) layer is formed on the N-type nitride semiconductor layer with Al _x In _y Ga _{1 -x- y} N (0≤x≤1, 0≤y≤1, 0≤x + y≤1),
Forming a multi-quantum well layer as an active layer on the ETB layer,
Forming a P-type nitride semiconductor layer on the multi-quantum well layer,
The ETB layer has an energy band gap larger than that of the N-type nitride semiconductor layer, constraining electrons tunneling the ETB layer from the N-type nitride semiconductor layer to the multi-quantum well layer, thereby forming the electrons and the P-type nitride semiconductor layer. And to increase the recombination rate between the holes injected into the multi-quantum well layer from the. The method of claim 1,
The thickness of the ETB layer is a method for manufacturing a semiconductor optical device, characterized in that 0.1 ~ 3.0 nm. The method of claim 1,
The ETB layer includes an Al _x In _{1 - x} N layer (0 <x <1), wherein x is 0.6 or more and less than 1. The method of claim 1,
The ETB layer is a semiconductor optical device manufacturing method, characterized in that the doped with at least one or more of the N-type dopant of Si, O, S, C, Ge, Zn, Cd, Mg. The method of claim 1,
Sapphire, GaN, SiC, AlN, ZnO, LiAlO ₂ , or LiGaO ₂ substrate is used as a substrate for forming the semiconductor optical device manufacturing method of a semiconductor optical device. The method of claim 1,
A method for manufacturing a semiconductor optical device comprising using a substrate having a crystal surface on which a nitride, polar, non-polar or semi-polar nitride semiconductor is grown as a substrate for forming the semiconductor optical device . An N-type nitride semiconductor layer;
The N-type nitride semiconductor layer ETB (Electron Tunneling Barrier) formed of _{Al x In y Ga 1 -x- y} N (0≤x≤1, 0≤y≤1, 0≤x + y≤1) above the floor;
A multiple quantum well layer formed as an active layer on the ETB layer; And
P-type nitride semiconductor layer formed on the multi-quantum well layer,
The ETB layer has an energy band gap larger than that of the N-type nitride semiconductor layer, constraining electrons tunneling the ETB layer from the N-type nitride semiconductor layer to the multi-quantum well layer, thereby forming the electrons and the P-type nitride semiconductor layer. And to increase the recombination rate between the holes injected into the multi-quantum well layer from. The method of claim 7, wherein
The semiconductor optical device includes a light emitting diode, a laser diode, a photodetector device or a solar cell.

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