KR20120131147A - Light emitting device and method for fabricating the same - Google Patents

Abstract

PURPOSE: A light emitting device and a manufacturing method thereof are provided to improve the crystallization of a p-type nitride semiconductor layer by forming an AlN/GaN layer of a super lattice structure between the p-type nitride semiconductor layer and an active layer to reduce current density. CONSTITUTION: A substrate is prepared(S01). A p-type AlN layer is grown by supplying source gas to a reactor(S03). The growth of the p-type AlN layer is stopped(S05). A u-GaN layer is grown on the p-type AlN layer by supplying Ga source gas and NH3 gas to the reactor(S07). The growth of the u-GaN layer is stopped by preventing the Ga source gas from being supplied to the reactor(S09). The p-type AlN layer and the u-GaN layer are repeatedly grown and the growths thereof are repeatedly stopped(S11). A p-type nitride semiconductor layer doped with Mg is grown by supplying source gas to the reactor(S13). [Reference numerals] (S01) Preparing substrate; (S03) Growing p-type AlN layer by supplying source gas; (S05) Stopping growth of p-type AlN layer; (S07) Growing u-GaN layer; (S09) Stopping growth of u-GaN layer; (S11) Repeating several times; (S13) Growing p-type nitride semiconductor layer

Description

LIGHT EMITTING DEVICE AND METHOD FOR FABRICATING THE SAME

The present invention relates to a light emitting device and a method of manufacturing the same, and more particularly, to a light emitting device having a superlattice p-type AlN / GaN layer between the p-type nitride semiconductor layer and the active layer and a method of manufacturing the same.

In general, nitride semiconductors are widely used in blue / green light emitting diodes or laser diodes as light sources for full color displays, traffic lights, general lighting and optical communication devices. The nitride-based light emitting device includes an active layer having a multi-quantum well structure positioned between n-type and p-type nitride semiconductor layers, and generates light by recombination of electrons and holes in the active layer.

These nitride semiconductor layers are mainly grown using a metal organic chemical vapor deposition method in which a nitride semiconductor layer is grown on the substrate by placing a substrate in the reactor and then supplying source gases using an organic source of a group III metal into the reactor. do.

Meanwhile, the p-type nitride semiconductor layer uses p-AlGaN as an electronic blocking layer (EBL), and is mainly formed using Mg as a dopant. In this case, Mg combines with hydrogen to deteriorate the crystallinity of the p-type nitride semiconductor layer. And at the same time may not contribute to the electrical conductivity of the p-type nitride semiconductor layer. This problem due to the doping of Mg causes an increase in leakage current, deterioration of reverse voltage characteristics and poor current diffusion of the light emitting device, thereby reducing the luminous efficiency and luminance of the light emitting device.

On the other hand, it is necessary to improve the electrical conductivity of the p-type nitride semiconductor layer in order to lower the driving voltage of the gallium nitride semiconductor light emitting device and improve its output. However, when the doping concentration of Mg is increased, a phenomenon in which the carrier concentration decreases, so-called self-compensation occurs.

Therefore, it is necessary to sufficiently increase the Mg doping concentration to improve the electrical conductivity of the p-type nitride semiconductor layer and to improve the crystallinity of the p-type nitride semiconductor layer.

SUMMARY OF THE INVENTION An object of the present invention is to provide a light emitting device having a p-type nitride semiconductor layer having improved electrical conductivity and / or crystallinity and a method of manufacturing the same.

According to an aspect of the present invention for solving the above problems, an n-type nitride semiconductor layer; An active layer formed on the n-type nitride semiconductor layer; An AlN / GaN layer having a superlattice structure formed by alternately repeatedly growing AlN and GaN on the active layer; Provided is a p-type nitride semiconductor layer formed on the AlN / GaN layer of the superlattice structure, at least one of the AlN and GaN is a p-type doped with a p-type dopant.

Preferably, the p-type nitride semiconductor layer may be p-GaN.

Preferably, the AlN / GaN layer of the superlattice structure may have the same amount of p-type dopant doped for each pair of the alternatingly grown AlN and GaN.

Preferably, the AlN / GaN layer of the superlattice structure may have a variable amount of p-type dopant doped for each pair of the alternatingly grown AlN and GaN.

Preferably, the p-type dopant may be Mg or Zn.

Preferably, the AlN may be p-AlN doped with a p-type dopant.

Preferably, in the AlN / GaN layer of the superlattice structure, the GaN may be formed thicker than the AlN.

According to another aspect of the invention, forming an n-type nitride semiconductor layer on a substrate; Forming an active layer on the n-type nitride semiconductor layer; Alternately repeatedly growing AlN and GaN on the active layer to form an AlN / GaN layer having a superlattice structure; And forming a p-type nitride semiconductor layer on the AlN / GaN layer of the superlattice structure, wherein at least one of the AlN and the GaN is a p-type doped with a p-type dopant. do.

Preferably, the p-type nitride semiconductor layer may be p-GaN.

Preferably, in the AlN / GaN layer of the superlattice structure, the GaN may be formed thicker than the AlN.

Preferably, forming the AlN / GaN layer of the superlattice structure is performed in a reactor, and supplies the source gases including p-type dopant source gas, N source gas, and Al source gas to the active layer. The p-type dopant-doped p-type AlN layer is grown thereon, and the p-type dopant source gas and the Al source gas supplied to the reactor are stopped to stop the growth of the p-type AlN layer, but supplies NH ₃ gas. And growing a u-GaN layer on the p-type AlN layer by supplying Ga source gas and NH ₃ gas into the reactor, and stopping the supply of the Ga source gas supplied into the reactor to stop the growth of the u-GaN layer. , NH ₃ gas may be supplied, and the above process may be repeated.

Preferably, the method performs the AlN / GaN layer forming step of the superlattice structure, and then supplying source gases including a Ga source gas, an N source gas, and a p-type dopant source gas into the reactor on the substrate. It may include growing the p-type nitride semiconductor layer doped with a p-type dopant.

Preferably, in the repetition of the above process, the p-type dopant source gas may be supplied at the same flow rate at each repetition.

Preferably, in the repetition of the process, the p-type dopant source gas may be supplied at different flow rates at each repetition.

The step of forming an AlN / GaN layer having a superlattice structure is performed in a reactor, and supplies p-type dopant to the active layer by supplying source gases including p-type dopant source gas, N-source gas, and Al-source gas into the reactor. Stop the growth of the p-type dopant source gas and the Al source gas supplied into the reactor and stop the growth of the p-type AlN layer, supplying NH ₃ gas, and supplying the reactor P-GaN layer is grown on the p-type AlN layer by supplying p-type dopant source gas, Ga source gas and NH ₃ gas into the p-type AlN layer, and p-type dopant source gas and Ga source gas supplied into the reactor are stopped. The growth of the GaN layer may be stopped, and NH ₃ gas may be supplied, and the above process may be repeated.

Preferably, the forming of the superlattice AlN / GaN layer is made in the reactor, by supplying the source gas containing the N source gas, Al source gas into the reactor to grow an AlN layer on the active layer , Stopping the supply of the Al source gas supplied into the reactor to stop the growth of the AlN layer, supplying NH ₃ gas, and supplying p-type dopant source gas, Ga source gas and NH ₃ gas into the reactor The p-GaN layer is grown on the layer, and the growth of the p-GaN layer is stopped by supplying the p-type dopant source gas and Ga source gas supplied into the reactor, supplying NH ₃ gas, and repeating the above process. Can be done.

The p-type dopant may be Mg or Zn, and the p-type dopant source gas may be CP ₂ Mg or DMZn.

According to embodiments of the present invention, by forming an AlN / GaN layer having a superlattice structure between the p-type nitride semiconductor layer and the active layer, the crystal defect density, for example, the dislocation density is reduced to improve the crystallinity of the p-type nitride semiconductor layer. Can be. Accordingly, a light emitting device having a low driving voltage and improved luminous efficiency and luminous output can be provided. In addition, by doping the Mg through the AlN / GaN layer of the superlattice structure to prevent the diffusion of the Mg can be appropriately doped where desired can increase the luminous efficiency.

1 is a cross-sectional view illustrating a light emitting device according to an embodiment of the present invention.
2 is a flowchart illustrating a method of manufacturing a light emitting device according to an embodiment of the present invention.
3 is a timing diagram illustrating a method of manufacturing a light emitting device according to an embodiment of the present invention.
Figure 4 is a graph showing the amount of light emitted according to the Mg flow rate change according to an embodiment of the present invention.
5 is a graph showing the amount of light emitted according to the flow rate of Al according to an embodiment of the present invention.

Hereinafter, with reference to the accompanying drawings will be described an embodiment of the present invention.

1 is a cross-sectional view illustrating a light emitting device according to an embodiment of the present invention.

Referring to FIG. 1, the light emitting device includes an n-type nitride semiconductor layer 25, an active layer 27, an AlN / GaN layer 28 having a superlattice structure, and a p-type nitride semiconductor layer 29. In addition, the light emitting device may include a substrate 21, a buffer layer 23, a transparent electrode layer 31, an n-electrode 33, and a p-electrode 35.

The substrate 21 refers to a wafer for fabricating a nitride-based light emitting device, and may be mainly sapphire (Al ₂ O ₃ ) or silicon carbide (SiC), but is not limited thereto. Heterogeneous substrates, such as silicon (Si), gallium arsenide (GaAs), spinel and the like, or a homogeneous substrate such as GaN.

The buffer layer 23 is used to mitigate lattice mismatch between the substrate 21 and the nitride semiconductor layer when the nitride semiconductor layer is grown on the substrate 21. The buffer layer 23 may be formed of an InAlGaN-based material or a SiC or ZnO-based material.

The n-type nitride semiconductor layer 25 may be mainly formed of GaN, but is not limited thereto. The n-type nitride semiconductor layer 25 may be formed of (Al, In, Ga) N-based binary to quaternary nitride semiconductors. In addition, the n-type nitride semiconductor layer 25 may be formed as a single layer or multiple layers, and may include a superlattice layer.

The active layer 27 may be formed of a single quantum well structure or a multi quantum well structure. In the case of a multi quantum well structure, the quantum barrier layer and the quantum well layer may be alternately formed two or more times and 20 times or less. . The active layer has a composition determined according to the required emission wavelength, and InGaN is suitable as an active layer (quantum well layer) to emit blue to green visible light. The quantum barrier layer is formed of nitride having a larger band gap than the quantum well layer, and may be formed of, for example, GaN or InGaN.

The superlattice AlN / GaN layer 28 has a superlattice structure formed by alternately growing AlN 28a and GaN 28b between the active layer 27 and the p-type nitride semiconductor layer 29. The superlattice AlN / GaN layer 28 can block the growth of dislocations into the p-type nitride semiconductor layer 29 grown thereon, thereby increasing the crystallinity of the p-type nitride semiconductor layer 29 and increasing the hole concentration. In addition, the diffusion of Mg in the AlN / GaN layer is also prevented, so that it can be appropriately doped where desired. In this case, the AlN / GaN layer 28 should be at least one of AlN and GaN p-type doped with a p-type dopant. For example, p-type AlN and u-GaN doped with Mg, p-GaN doped with AlN and Mg doped, p-GaN doped with Mg and p-GaN doped with Mg have. Herein, the use of Mg as the p-type dopant will be described. However, the present invention is not limited thereto, and Zn may be used in addition to the present invention.

In addition, in the AlN / GaN layer 28 of the superlattice structure, GaN 28b is preferably formed thicker than AlN 28a. By doing so, it is possible to prevent the Vf from increasing and the crystalline from falling.

The p-type nitride semiconductor layer 29 may be mainly formed of GaN, but is not limited thereto. The p-type nitride semiconductor layer 29 may be formed of (Al, In, Ga) N-based binary to quaternary nitride semiconductors. The p-type nitride semiconductor layer 29 is formed using Mg as a dopant.

The transparent electrode layer 31 is positioned on the p-type nitride semiconductor layer 29, and the transparent electrode layer 31 may be formed of a transparent metal layer such as Ni / Au or a conductive oxide such as ITO.

The n-electrode 33 may be formed on the n-type nitride semiconductor layer 25, and the p-electrode may be formed on the transparent electrode layer 31. The n-electrode and p-electrode may be formed of various metal materials such as Ti / Al.

The buffer layer, the n-type nitride semiconductor layer, and the active layer may include metal organic chemical vapor deposition (MOCVD), molecular beam growth (MBE), and hydride vapor growth (HVPE). Although it can be formed using a variety of techniques, such as metal organic chemical vapor deposition method is currently used. Therefore, hereinafter, a method of forming the p-type nitride semiconductor layer using the metal organic chemical vapor deposition method will be described.

2 is a flowchart illustrating a method of manufacturing a light emitting device according to an embodiment of the present invention, Figure 3 is a timing diagram for explaining a method of manufacturing a light emitting device according to an embodiment of the present invention.

Referring to FIG. 2, first, a substrate 21 is prepared (S01). The substrate 21 may have a buffer layer 23, an n-type nitride semiconductor layer 25, and an active layer 27 thereon. The substrate 21 may be prepared by loading the substrate 21 into the reactor and supplying source gases into the reactor to deposit the buffer layer 23, the n-type nitride semiconductor layer 25, and the active layer 27.

The buffer layer 23 may be formed of nitride, and a method and a material for forming the buffer layer are well known, and thus detailed description thereof will be omitted.

The n-type nitride semiconductor layer 25 may be generally formed using Si as a dopant, and an inert gas such as SiH ₄ or Si ₂ H ₄ , or a metal organic source such as DTBSi may be used as the source of Si. . The Si concentration may range from 1 × 10 ¹⁷ / cm 3 to 5 × 10 ¹⁹ / cm 3, and the n-type nitride semiconductor layer may be formed to a thickness of 1.0 μm to 5.0 μm.

The active layer 27 has a single quantum well structure, or two In _x Ga1 _{1- x} N (0.1 <x <1) quantum well layers and two In _y Ga _{1- y} N (0 <y <0.5) quantum barrier layers. It may be formed of a multi-quantum well structure repeatedly stacked more than 20 times. Preferably, each quantum well layer may be formed of 1 ~ 5nm thickness and In content (0.1 <x <0.4), each quantum barrier layer is formed of 5 ~ 40nm thickness and In content (0 <y <0.2) Can be.

2 and 3, the p-type dopant source, the N source gas, and the Al source gases are supplied into the reactor to grow the p-type AlN layer 28a (S03). The supply of source gases is done for T1 time.

As the p-type dopant source, CP ₂ Mg or DMZn may be used. As the N source gas, ammonia (NH ₃ ) or dimethylhydrazine (DMHy) may be used, and as an Al source gas, trimethyl aluminum (TMAl, Al ( CH ₃ ) ₃ ) can be used. Here, a description will be given of the case where CP ₂ Mg, which is an Mg source gas, is used as the p-type dopant source gas, but the present invention is not limited thereto.

The T1 time may be set to the time required to form the AlN layer 28a of the required thickness.

Thereafter, the supply of the Mg source gas and the Al source gas supplied into the reactor is stopped to stop the growth of the p-type AlN layer (S05). The growth stop is during T2 time.

The reactor is equipped with an exhaust pump to discharge the gases in the reactor, so that over time after the supply of the source gases is stopped, the Mg source gas and Al source gas remaining in the reactor are mostly discharged to the outside. The T2 time may be 1 to 60 seconds as a time for discharging the Mg source gas and the Al source gas.

If the growth is stopped at a relatively high temperature, nitrogen atoms in the nitride semiconductor layer grown on the substrate may dissociate to form nitrogen cavities. Therefore, it is possible to supply N atoms by supplying NH ₃ gas during growth stop of the nitride semiconductor layer. In the present embodiment, when the N source gas includes NH ₃ , the supply of the Mg source gas and the Al source gas may be stopped and the NH ₃ may be continuously supplied. Alternatively, the N source gas can be supplied to the NH ₃ separately in the case that does not contain NH _3, the growth interruption step (S05).

Thereafter, Ga source gas and NH ₃ gas are supplied into the reactor to grow a u-GaN layer 28b on the p-type AlN layer 28a (S07). As the Ga source, trimethylgallium (TMGa) or triethylgallium (TEGa) can be used.

The growth of the u-GaN layer 28b is performed for T3 time, and T3 may be in the range of 1 to 60 seconds.

Thereafter, the supply of the Ga source gas supplied into the reactor is stopped to stop the growth of the u-GaN layer 28b (S09). The growth stop is during T4 hours.

The reactor is equipped with an exhaust pump to discharge the gas in the reactor, and as time passes after the supply of the Ga source gas is stopped, most of the Ga source gas remaining in the reactor is discharged to the outside. The T4 time may be 1 to 60 seconds as a time for discharging the Ga source gas.

The growth, growth stop, growth of the u-GaN layer 28b and growth stop of the p-type AlN layer 28a described above are repeated several times (S11). In this case, the grown p-type AlN layer 28a and the u-GaN layer 28b may be formed to have a total thickness of 300-400 적층. The superlattice AlN / GaN layer 28 may form 10 to 100 pairs. Accordingly, the thicknesses of the p-type AlN layer 28a and the u-GaN layer 28b constituting the superlattice structure may be determined as thicknesses for implementing the entire thickness.

When the nitride semiconductor layers are grown using MOCVD, the n-type nitride semiconductor layer 25, the active layer 27, the superlattice AlN / GaN layer 28 and the p-type nitride semiconductor layer 29 in the same reactor. This can be grown.

The Ga source gas, the N source gas, and the Mg source gas are supplied into the reactor again to grow the Mg-doped p-type nitride semiconductor layer 29 (S13).

After that, by patterning the p-type nitride semiconductor layer 29 and the active layer 27 formed on the substrate 21, by forming a transparent electrode layer 31, n-electrode 33 and p-electrode 35 The light emitting device of FIG. 1 is completed.

According to embodiments of the present invention, a superlattice AlN / GaN structure in which a p-type AlN layer 28a and a u-GaN layer 28b are alternately stacked between the p-type nitride semiconductor layer 29 and the active layer 27. The formation of the layer 28 prevents the growth of dislocations into the nitride semiconductor layer grown thereon, thereby increasing the crystallinity of the p-type nitride semiconductor layer 29 and increasing the hole concentration, and the AlN / GaN layer 28. The diffusion of Mg in the c) can also be prevented, so that it can be appropriately doped where desired.

Experiment 1

In Experiment 1, the light emission effect of the Mg flow rate during the growth of the superlattice p-type AlN / u-GaN layer was measured.

Temperature 980 ° C.,

-Mg 120sccm, 180sccm, 240sccm, 300sccm, 360sccm, 480sccm

60 pairs of p-type AlN / u-GaN layers; time 0.1 min / 0.1 min

4 is a graph showing the amount of light emitted according to the flow rate of Mg. As shown in FIG. 4, it can be seen that the total amount of light emitted is increased by using an AlN / GaN layer having a superlattice structure. There was a difference in light emission according to the flow rate of Mg during the growth of the AlN / GaN layer.

Experiment 2

In Experiment 2, the effect of Al emission on the growth of superlattice p-type AlN / u-GaN layer was measured.

Temperature 980 ° C.,

Al: 32/40/31 (-10%); 40/40/31; 49/40/31 (+ 10%)

60 pairs of p-type AlN / u-GaN layers; time 0.1 min / 0.1 min

5 is a graph showing the amount of light emitted according to the flow rate of Al. As can be seen in Figure 5 it can be seen that the total amount of light emission is increased by using the AlN / GaN layer of the superlattice structure. The growth of AlN / GaN layer showed a difference in the amount of light emitted by the flow rate of Al.

The p-type nitride semiconductor layer forming method of the present embodiment can be used to manufacture not only light emitting diodes but also other nitride optical devices such as laser diodes.

Although the present invention has been described in detail with reference to preferred embodiments, the scope of the present invention is not limited to the specific embodiments, it should be interpreted by the appended claims. In addition, those of ordinary skill in the art will understand that many modifications and variations are possible without departing from the scope of the present invention.

For example, in the present embodiments, when describing an AlN / GaN layer having a superlattice structure, the AlN layer is first grown and then the GaN layer is grown, but the present invention is not limited thereto. A process of growing may be performed, and then a process of growing an AlN layer may be performed.

Further, in the present embodiments, when AlN and GaN are alternately stacked to form a pair of superlattice AlN / GaN layers, the amount of Mg is constant for each pair, but the present invention is limited thereto. Instead, it is also possible to vary the amount of Mg, for example, by gradually decreasing or gradually increasing the amount of Mg for each pair of AlN / GaN layers.

Further, in the present embodiments, AlN / GaN made of p-type AlN and u-GaN has been described, but the present invention is not limited thereto.

For example, in performing the AlN / GaN layer forming step of the superlattice structure, Mg doped on the active layer by supplying source gases including Mg source gas, N source gas, and Al source gas into the reactor. Growing a p-type AlN layer, and stops the supply of the Mg source gas, Al source gas supplied into the reactor to stop the growth of the p-type AlN layer, supplying NH ₃ gas, into the reactor, Mg source gas, By supplying a Ga source gas and NH ₃ gas to grow a p-GaN layer on the p-type AlN layer, by stopping the supply of the Mg source gas, Ga source gas supplied into the reactor to stop the growth of the p-GaN layer, By supplying NH ₃ gas and repeating the above process, a superlattice AlN / GaN layer including Mg-doped p-type AlN and Mg-doped p-GaN can be formed.

In addition, in performing the AlN / GaN layer forming step of the superlattice structure, by supplying the source gas containing the N source gas, Al source gas into the reactor to grow an AlN layer on the active layer, is supplied to the reactor The growth of the AlN layer is stopped by supplying Al source gas, supplying NH ₃ gas, and supplying Mg source gas, Ga source gas and NH ₃ gas into the reactor to grow a p-GaN layer on the AlN layer. And stopping the growth of the p-GaN layer by stopping the supply of the Mg source gas and the Ga source gas supplied into the reactor, supplying NH ₃ gas, and repeating the above procedure, thereby performing Mg-doped AlN and A superlattice AlN / GaN layer made of Mg doped p-GaN can be formed.

In addition, in an embodiment of the present invention, a case of Mg as a p-type dopant, and thus Cp ₂ Mg as a p-type dopant source gas, has been described. It can also be implemented.

Claims (7)

an n-type nitride semiconductor layer;
An active layer formed on the n-type nitride semiconductor layer;
An AlN / GaN layer having a superlattice structure formed by alternately repeatedly growing AlN and GaN on the active layer;
It includes a p-type nitride semiconductor layer formed on the AlN / GaN layer of the superlattice structure,
At least one of the AlN and the GaN is a p-type doped with a p-type dopant. The method according to claim 1,
The p-type nitride semiconductor layer is a light emitting device, characterized in that p-GaN. The AlN / GaN layer of the superlattice structure according to claim 1,
Wherein the amount of p-type dopants doped for each pair of alternatingly grown AlN and GaN is the same. The AlN / GaN layer of the superlattice structure according to claim 1,
Wherein the amount of p-type dopant doped for each pair of alternatingly grown AlN and GaN is variable. The method according to claim 1,
The p-type dopant is Mg or Zn characterized in that the light emitting device. The method according to claim 1,
Wherein said AlN is p-AlN doped with a p-type dopant. The AlN / GaN layer of the superlattice structure according to claim 1,
The GaN is light-emitting device, characterized in that formed thicker than the AlN.

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