Lighting device and method for its manufacture

Abstract

A lighting device comprising: an n-type semiconductor layer (25); a p-type semiconductor layer (40); an active layer (29) arranged between the n-type semiconductor layer (25) and the p-type semiconductor layer (40); and an electron-blocking layer (31) located between the p-type semiconductor layer (40) and the active layer (29), where: the p-type semiconductor layer (40) comprises a hole injection layer (33), a p-type contact layer (37) and a hole transport layer (35) arranged between the hole injection layer (33) and the p-type contact layer (37), the hole transport layer (35) comprises several undoped layers (35a) and at least one doped intermediate layer (35b) between the undoped layers (35a), at least one of the undoped layers (35a) comprises a zone in which the hole concentration decreases with increasing distance to the hole injection layer (33) or the p-type contact layer (37), and the doped intermediate layer (35b) is arranged such that it overlaps at least partially with a region of the hole transport layer (35) in which the hole concentration of the hole transport layer (35) is 62% to 87% of the hole concentration of the p-type contact layer (37), and at least one of the undoped layers (35a) furthermore comprises a zone in which the hole concentration increases with decreasing distance to the doped intermediate layer (35b), wherein the zone in which the hole concentration increases with decreasing distance from the doped intermediate layer (35b) includes a region in which the hole concentration increases linearly.

Description

TECHNICAL FIELD

[0001] Exemplary embodiments of the disclosure relate to a lighting device in the form of a nitride semiconductor with a p-type semiconductor layer and a method for its manufacture. BACKGROUND

[0002] In general, a light-emitting device using nitride semiconductors comprises an n-type semiconductor layer, an active layer, and a p-type semiconductor layer. In the active layer, electrons and holes recombine to emit light. The recombination rate of electrons and holes in the active layer directly affects the light-emitting efficiency of the device. To improve the recombination rate of electrons and holes in the active layer, electron overflow must be prevented. For this purpose, an electron-blocking layer, in the form of a p-type AIGAN layer, is employed. Such light-emitting devices with a nitride semiconductor, in which an active, light-emitting layer includes an electron-blocking layer, are disclosed, for example, in US 2007 / 0096077A1 and US 2009 / 0020780A1.The electron-blocking layer is a layer made of a material with a large band gap. SUMMARY

[0003] It is an object of the present invention to provide a lighting device with improved efficiency and a method for manufacturing it. This object is achieved by a lighting device having the features of claim 1 and a manufacturing method having the features of claim 8.

[0004] Exemplary embodiments of the disclosure provide a lighting device that has improved internal quantum efficiency due to improved injection efficiency in an active layer, as well as a method for its fabrication.

[0005] Exemplary embodiments of the disclosure provide a lighting device, including a p-type semiconductor layer with a structure that can improve hole mobility, and a method for its fabrication.

[0006] According to one aspect of the present disclosure, a lighting device comprises: an n-type semiconductor layer; a p-type semiconductor layer; an active layer between the n-type semiconductor layer and the p-type semiconductor layer; and an electron-blocking layer between the p-type semiconductor layer and the active layer, wherein the p-type semiconductor layer comprises a hole injection layer, a p-type contact layer, and a hole transport layer between the hole injection layer and the p-type contact layer. The hole transport layer consists of several undoped layers and at least one doped intermediate layer between the undoped layers.At least one of the undoped layers includes a zone in which the hole concentration decreases with increasing distance from the hole injection layer or the p-type contact layer, and the doped intermediate layer is designed to be at least partially overlapped by a region of the hole transport layer, wherein the hole concentration of the hole transport layer is 62% to 87% of the hole concentration of the p-type contact layer.

[0007] The injection layer can have a doping concentration of 1E20 / cm². 3 (1·1020 / cm 3 ) up to 5E20 / cm 3 (5·1020 / cm 3 ) have, the p-type contact layer can have a dopant concentration of 4E20 / cm² 3 or more, and the doped intermediate layer can have a dopant concentration of 1E18 / cm² 3 up to 1E20 / cm 3 have.

[0008] The hole transport layer can have a greater thickness 5 than the total thickness of the hole injection layer and p-type contact layer.

[0009] The doped intermediate layer can have a thickness of 10 nm to 20 nm, and the undoped layers can have a thickness of 15 nm to 30 nm.

[0010] The hole injection layer can border the electron blocking layer.

[0011] The zone in which the hole concentration decreases with increasing distance from the hole injection layer or the p-type contact layer may include a region in which the hole concentration decreases linearly.

[0012] According to the invention, at least one of the undoped layers further comprises a zone in which the hole concentration increases with decreasing distance to the doped intermediate layer.

[0013] According to the invention, the zone in which the hole concentration increases with decreasing distance from the doped intermediate layer comprises a region in which the hole concentration increases linearly.

[0014] The doped intermediate layer can have a higher electrical resistance than the undoped layers.

[0015] According to another aspect of the present disclosure, a method for manufacturing such a luminaire comprises the following: growing an n-type semiconductor layer, an active layer, an electron-blocking layer, and a p-type semiconductor layer on a substrate within a chamber by means of metal-organic chemical vapor deposition, wherein the growth of the p-type semiconductor layer also includes growing a hole injection layer on the substrate within the chamber by supplying an N source gas, a Ga source gas, a Mg source gas, N2 gas, and H2 gas to the chamber; growing an undoped layer on the hole injection layer by supplying an N source gas, a Ga source gas, and N2 gas to the chamber while simultaneously blocking the supply of the Mg source gas and H2 gas; and growing a doped intermediate layer on the undoped layer by supplying an N source gas.The process includes the introduction of a Ga source gas, N2 gas and a Mg source gas into the chamber, the growth of an undoped layer on the doped intermediate layer by introducing an N source gas, a Ga source gas and N2 gas into the chamber while simultaneously blocking the supply of Mg source gas, and the growth of a p-type bonding layer on the undoped layers by introducing an N source gas, a Ga source gas, a Mg source gas, N2 gas and H2 gas into the chamber.

[0016] The manufacturing process can also include the injection of an N source gas and N2 gas into the chamber while simultaneously blocking the supply of the Ga source gas, the Mg source gas and H2 gas in order to change the atmosphere of the chamber to an atmosphere of nitrogen and NH3 before the hole injection layer is developed.

[0017] The atmosphere of the chamber can be changed to an atmosphere of nitrogen and NH3 over 3 to 10 minutes.

[0018] During the growth of the hole injection layer and the p-type contact layer, the flow rate of H2 gas can be higher than the flow rate of N2 gas.

[0019] During the growth of the hole injection layer and the p-type contact layer, the flow rate of H2 gas can be three to five times higher than the flow rate of N2 gas.

[0020] During the growth of the hole injection layer and the p-type contact layer, the flow rate of NH3 gas may be lower than the flow rate of H2 gas, and during the growth of the hole transport layer, the flow rate of N2 gas may be higher than the flow rate of NH3 gas.

[0021] During the growth of the hole injection layer and the p-type contact layer, N2, H2 and NH3 can be injected at a flow rate ratio of 1:3:1, and during the growth of the hole transport layer, N2, H2 and NH3 can be injected at a flow rate ratio of 3:0:1.

[0022] The manufacturing process may also include heat pretreatment of the p-type semiconductor layer within the chamber after the growth of the p-type contact layer.

[0023] The injection layer can have a doping concentration of 1E20 / cm². 3 up to 5E20 / cm 3 The p-type contact layer can have a dopant concentration of 4E20 / cm² 3 or more, and the doped intermediate layer can have a dopant concentration of 1E18 / cm² 3 up to 1E20 / cm 3 have.

[0024] According to the embodiments disclosed, the illuminating device comprises a p-type semiconductor layer containing a hole transport layer. A doped interlayer is present between undoped layers to increase hole mobility, thereby enhancing the hole injection efficiency of the illuminating device. Furthermore, during the growth of the hole transport layer, the supply of H₂ gas is blocked to reduce the dopant concentration in the undoped layers, further increasing hole mobility in the hole transport layer. Due to the increased resistance of the doped interlayer in the hole transport layer, electric current generated by an electrostatic discharge can be blocked by the doped interlayer, thus improving the resistive-voltage characteristics of the illuminating device under electrostatic discharge. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a schematic sectional view of an exemplary lighting device according to an exemplary embodiment of the disclosure. Fig. Figure 2 is a diagram showing profiles of a hole concentration and a Mg concentration of the lighting device according to the exemplary embodiment of the disclosure. Fig. Figure 3 is a diagram showing gas and temperature profiles to illustrate a method for manufacturing the lighting device according to the exemplary embodiment of the disclosure. Fig. 4 and Fig. Figure 5 shows diagrams illustrating the power, forward voltage and resistance voltage of the electrostatic discharge for an example according to the invention and a comparative example. DETAILED DESCRIPTION OF EXAMPLE EXECUTIONS

[0025] Exemplary embodiments of this disclosure are described in more detail below with reference to the accompanying drawings. The following embodiments are given only as examples to convey the meaning of this disclosure to those skilled in the art, to whom this disclosure is addressed. Accordingly, this disclosure is not limited to the embodiments disclosed herein and may also be implemented in other forms. In the drawings, the widths, lengths, thicknesses, and similar properties of elements may be exaggerated for clarity and descriptive purposes. When an element or layer is said to be "attached to" another element or layer, it may be "attached" directly to the other element or layer, or there may be intermediate elements or layers.Throughout the specification, similar reference numbers denote similar elements that have the same or similar functions.

[0026] To increase the hole injection efficiency from a p-type semiconductor layer to an active layer, the doping profile of the p-type semiconductor layer can be controlled. For example, a hole injection layer and a p-type contact layer can be separated, and the dopant concentration of the hole injection layer can be adjusted to be lower than that of the p-type contact layer to improve hole injection efficiency. Furthermore, an undoped layer can be formed between an encapsulating layer and the hole injection layer, or between the hole injection layer and the p-type contact layer.

[0027] These techniques make it possible to promote the movement of the injected holes into the active layer by increasing hole mobility within the injection layer. However, even with these techniques, there is a limit to increasing hole mobility, as the injection layer is doped with a relatively low dopant concentration.

[0028] Fig. Figure 1 is a schematic sectional view of an exemplary lighting device according to an exemplary embodiment of the disclosure, and Fig. Figure 2 is a diagram showing profiles of a hole concentration and a Mg concentration of the lighting device according to the exemplary embodiment of the disclosure.

[0029] Referring to Fig. 1 The lighting device can comprise a substrate 21, a buffer layer 23, an n-type semiconductor layer 25, a superlattice layer 27, an active layer 29, an electron-blocking layer 31 and a p-type semiconductor layer 40.

[0030] Substrate 21 can be, for example, a patterned sapphire substrate, a spinel substrate, a silicon carbide substrate, or a gallium nitride substrate.

[0031] The buffer layer 23 can comprise a low-temperature buffer layer and a high-temperature buffer layer. If the substrate 21 is a gallium nitride substrate, the buffer layer 23 can be omitted.

[0032] The n-type semiconductor layer 25 can include an n-type contact layer. The n-type semiconductor layer 25 can be formed from or contain a (Al, Ga, In)N-based group III nitride semiconductor layer and can consist of a single layer or multiple layers. For example, the n-type semiconductor layer 25 includes a GaN layer and can be formed by doping with an n-type dopant, for example, Si.

[0033] The superlattice layer 27 can be adopted to enhance the current distribution while simultaneously improving the crystal quality of the active layer. The superlattice layer 27 can be formed by repeated stacking, for example, GaN / InGaN or InGaN / InGaN. However, the superlattice layer 27 is not limited to this and can also comprise a structure in which nitride semiconductor layers such as (Al, Ga, In)N are repeatedly stacked on top of each other in at least two layers.

[0034] The active layer 29 is located between the n-type semiconductor layer 25 and the p-type semiconductor layer 40 and can have a single-quantum or multi-quantum well structure in which the well layers and barrier layers are stacked alternately. The well layer can be made of or contain, for example, InGaN, and the barrier layer can be made of or contain a gallium nitride-based semiconductor, such as GaN, which has a larger band gap than the well layer.

[0035] The electron-blocking layer 31 is located between the active layer 29 and the p-type semiconductor layer 40 and prevents electrons from flowing from the active layer 29 into the p-type semiconductor layer 40. The electron-blocking layer 31 can be made of or contain a gallium nitride-based semiconductor, which generally has a larger band gap than the p-type semiconductor layer 40. For example, if the barrier layer contains GaN, the electron-blocking layer 31 can contain AlGaN.

[0036] The p-type semiconductor layer 40 contains a hole injection layer 33, a hole transport layer 35, and a p-type contact layer 37. In addition, the hole transport layer 35 can include undoped layers 35a and a doped intermediate layer 35b.

[0037] The hole injection layer 33, the hole transport layer 35, and the p-type contact layer 37 can be gallium nitride-based semiconductor layers, for example, GaN layers, with the same composition except for the dopant concentration. Accordingly, a hole provided by an electrode (not shown) can pass through the p-type semiconductor layer 40 without being blocked by an energy barrier. The hole injection layer 33 can be adjacent to the electron-blocking layer 31. Furthermore, the p-type contact layer 37 can be in contact with an electrode (not shown).

[0038] The hole transport layer 35 can have a greater thickness than the combined thickness of the hole injection layer 33 and the p-type contact layer 37. For example, the hole injection layer 33 can have a thickness of 5 nm to 20 nm, the hole transport layer 35 can have a thickness of 50 nm to 100 nm, and the p-type contact layer 37 can have a thickness of 10 nm to 30 nm. Furthermore, in the hole transport layer 35, each of the undoped layers 35a can have a thickness of 15 nm to 30 nm, and the doped intermediate layer 35b can have a thickness of 10 nm to 20 nm. In this embodiment, each of the undoped layers 35a can have a thickness of approximately 22 nm, and the doped intermediate layer 35b can have a thickness of approximately 15 nm. Thus, the hole transport layer 35, including the undoped layers and the intermediate layer, can have a thickness of approximately 60 nm. However, it is agreed that the present disclosure is not limited to this and that other implementations are also possible.

[0039] The hole injection layer 33 can have a doping concentration of 1E20 / cm² 3 up to 5E20 / cm 3 and the p-type contact layer 37 has a dopant concentration of 4E20 / cm² 3 or more. Furthermore, the doped intermediate layer 35b of the hole transport layer can have a dopant concentration of 1 E18 / cm². 3 up to 1E20 / cm 3 In this embodiment, the doped intermediate layer 35b can have a dopant concentration of 1 E19 / cm². 3 having is not limited to that.

[0040] In this embodiment, the hole transport layer 35 can be relatively thick and includes the doped intermediate layer 35b to achieve a significant increase in hole mobility, thus improving the hole injection rate into the active layer 29. This structure is described in more detail below.

[0041] Holes injected into the p-type contact layer 37 can spread across the hole transport layer 35 depending on the hole scattering distance. The hole scattering distance can be represented by Equation 1: Lp=u×t where Lp is a hole dispersion distance, u is the hole mobility, and t is the lifetime of a hole.

[0042] According to Equation 1, holes of the p-type contact layer 37 can spread into the hole transport layer 35, and the hole scattering distance is the distance from the p-type contact layer 37 to a point where the hole concentration becomes 0. Furthermore, if the hole concentration is sufficiently higher than an electron concentration, the hole concentration of the hole transport layer 35 can decrease with increasing distance from the p-type contact layer 37 or the hole injection layer 33. In the present disclosure, the hole transport layer 35 comprises the undoped layers 35a, and at least one of the undoped layers 35a can include a zone in which the hole concentration decreases proportionally with increasing distance from the p-type contact layer 37 or the hole injection layer 33.The zone in which the hole concentration decreases can include a region where the hole concentration decreases linearly with increasing distance from the p-type contact layer 37, but is not limited to it. The hole concentration can also decrease non-linearly. For example, the gradient of the hole concentration with increasing distance from the p-type contact layer 37 or the hole injection layer 33 in the hole transport layer 35 can increase or decrease. Furthermore, at least one of the undoped layers 35a can include a zone where the hole concentration increases with decreasing distance to the doped intermediate layer 35b. The zone where the hole concentration increases can include a region where the hole concentration decreases linearly with decreasing distance from the doped intermediate layer 35b, but is not limited to it.

[0043] For example, Fig. 2 a diagram showing profiles of a hole concentration and a Mg concentration of the lighting device according to the exemplary embodiment of the disclosure. In Fig. Figure 2 shows a lower diagram showing a concentration profile of p-type dopants, i.e., Mg, in the direction of increasing distance from the active layer, and an upper diagram showing a concentration profile of holes in the direction of increasing distance from the active layer.

[0044] Referring to Fig. 2. The hole injection layer 33, the p-type contact layer 37, and the doped intermediate layer 35b each contain a predetermined concentration of p-type dopants (Mg). The hole injection layer 33 may have a higher Mg concentration than the doped intermediate layer 35b, and the p-type contact layer 37 may have a higher Mg concentration than the hole injection layer 33. In contrast, the undoped layers 35a may have a significantly lower Mg concentration than the hole injection layer 33, the p-type contact layer 37, and the doped intermediate layer 35b, or may be essentially free of Mg. The undoped layers 35a can be developed by interrupting the supply of Mg, resulting in an effective Mg concentration of 0. This means that the undoped layers 35a are intended to contain no p-type dopants.In some embodiments, however, the undoped layers 35a may contain a trace amount of Mg because the Mg source remains in the coating chamber, and may also contain Mg released from at least one layer of the hole injection layer 33, the p-type contact layer 37, and the doped intermediate layer 35b due to Mg scattering. Accordingly, embodiments in which the undoped layers 35a unintentionally contain Mg are also within the scope of this disclosure.

[0045] As in Fig. As shown in Figure 2, the hole injection layer 33 has a predetermined hole concentration, and the hole concentration of the undoped layer 35a, which borders the hole injection layer 33, gradually decreases with increasing distance from the active layer. Here, the hole concentration can decrease linearly, at least in some zones. In the undoped layer 35a, the hole concentration gradually decreases with increasing distance from the hole injection layer 33 and then increases again with decreasing distance to the doped intermediate layer 35b. Similarly, the hole concentration of the undoped layer 35a near the p-type contact layer 37 can gradually decrease with increasing distance from the doped intermediate layer 35b and then increase again with decreasing distance to the p-type contact layer 37. Here, the hole concentration can decrease linearly, at least in some zones.

[0046] According to the present disclosure, the doped intermediate layer 35b in the hole transport layer 35 can overlap with a region of the hole transport layer where the hole concentration of the hole transport layer is 62% to 87% of the hole concentration of the p-type contact layer 37. That is, the doped intermediate layer 35b can be arranged to overlap at least partially with a region of the hole transport layer where the hole concentration of the hole transport layer is 62% to 87% of the hole concentration of the p-type contact layer 37. In this configuration, the doped intermediate layer 35b, containing dopant at a predetermined concentration in the hole transport layer 35, which includes the undoped layers 35a, is designed to enhance the hole mobility.That is, the doped intermediate layer 35b is positioned downstream of a zone where the concentration of holes supplied by the p-type contact layer 37 is reduced to a specific hole concentration, and it acts as a stepping stone, thereby increasing the hole mobility in the hole transport layer 35 to enhance the hole injection rate into the active layer 29, thus improving the internal quantum efficiency. In this embodiment, the doped intermediate layer 35b can be positioned closer to the hole injection layer 33 than to the p-type contact layer 37, without being restricted to it.

[0047] In the lighting device according to the embodiments described above, the doped intermediate layer 35b can have a relatively high resistance. Therefore, if static electricity is induced in the lighting device, the electric current resulting from the static electricity can be blocked by the doped intermediate layer 35b with its relatively high resistance, thereby improving the resistance properties of the electrostatic discharge of the lighting device.

[0048] Fig. Figure 3 is a diagram illustrating gas and temperature profiles for the purpose of producing the lighting device, in particular a method for growing a p-type semiconductor layer 40 according to an exemplary embodiment of the disclosure. In this embodiment, the p-type semiconductor layer 40 can be developed by metal-organic chemical vapor deposition, and a buffer layer 23, an n-type semiconductor layer 25, a superlattice layer 27, an active layer 29, and an electron-blocking layer 31 can also be developed in situ by metal-organic chemical vapor deposition in the same chamber.

[0049] Referring to Fig. 1 and Fig. In three stages, in which a substrate 21 is charged within the chamber, a metal source gas, an N source gas, and a carrier gas or gas atmosphere are introduced into the chamber to develop semiconductor layers, including the buffer layer 23, the n-type semiconductor layer 25, the superlattice layer 27, the active layer 29, the electron-blocking layer 31, and similar layers. A source gas of n-type dopants can be introduced into the chamber as needed.

[0050] The metal source gas contains at least one Ga source gas, Al source gas, or In source gas, and a suitable source gas is introduced depending on the metal components of a gallium nitride-based semiconductor layer to be developed in the chamber. For example, TMGa or TEGa can generally be used as the Ga source gas; TMAl or TEAl can be used as the Al source gas; and TMIn or TEIn can be used as the In source gas.

[0051] NH3 can generally be used as the nitrogen source gas, and SiH4 can be used as the source gas for n-type dopants. Furthermore, N2 and / or H2 can be used as the carrier gas or gas atmosphere.

[0052] After the electron-blocking layer 31 has grown, the p-type semiconductor layer 40 is developed within the chamber by metal-organic chemical vapor deposition. The p-type semiconductor layer 40 can generally be developed at a pressure of 133 mbar to 400 mbar.

[0053] First, a hole injection layer 33 is developed on the electron-blocking layer 31 at a temperature of, for example, 970°C to 990°C. The hole injection layer 33 can be developed by feeding the nitrogen source gas (for example, NH3) and the gallium source gas (for example, TMGa and / or TEGa) together with a magnesium source gas (for example, Cp2Mg), nitrogen gas, and hydrogen gas into the chamber. In this case, the nitrogen gas can be fed in at a flow rate of approximately 30 l / min to approximately 50 l / min, the hydrogen gas at a flow rate of approximately 140 l / min to approximately 160 l / min, and the NH3 gas at a flow rate of approximately 30 l / min to approximately 50 l / min. For example, the flow rate ratio of N2:H2:NH3 can be 1:3:1. Furthermore, the flow rate of the Mg source gas is selected so that a suitable dopant concentration is achieved, and the hole injection layer 33 can have a Mg concentration of about 1E20 / cm². 3 up to about 5E20 / cm 3 have.

[0054] After the hole injection layer 33 has grown, undoped layers 35a of the hole transport layer 35 are developed at a temperature of, for example, 940°C to 970°C. The undoped layers 35a are developed by feeding the nitrogen source gas (for example, NH3), the gallium source gas (for example, TMGa or TEGa), and nitrogen gas into the chamber while blocking the feed of the magnesium source gas and the hydrogen gas. For example, the nitrogen source gas can be fed in at a flow rate of approximately 140 l / min to approximately 160 l / min, the hydrogen source gas at a flow rate of approximately 0 l / min, and the NH3 gas at a flow rate of approximately 30 l / min to approximately 50 l / min. More precisely, the flow rate ratio of N2:H2:NH3 can be 3:0:1.

[0055] Generally, even if the Mg source gas is not injected, Mg is injected from the hole injection layer 33 into the undoped layer 35a during the growth of the undoped layer 35a. If H₂ gas is injected during the growth of the undoped layers 35a, the supply of Mg can be further enhanced. Accordingly, the dopant concentration of the undoped layers 35a can be reduced by blocking the injection of H₂ during the growth of the undoped layers 35a. On the other hand, the Mg source gas is supplied during the growth of the undoped layer 35a to develop a doped intermediate layer 35b. Then, after the growth of the doped intermediate layer 35b is complete, another undoped layer 35a is developed by blocking the Mg source gas onto it, thereby forming the hole transport layer 35 according to the exemplary embodiment of the disclosure.

[0056] Furthermore, the flow rate of the Mg source gas is selected such that a suitable dopant concentration is achieved, and the doped intermediate layer 35b of the hole transport layer 35 can have a Mg concentration of about 1E18 / cm². 3 up to about 1E20 / cm 3 Furthermore, the doped intermediate layer 35b has a Mg concentration that is higher than that of the undoped layers 35a and lower than that of the hole injection layer 33.

[0057] On the other hand, the atmosphere of the chamber can be changed to a nitrogen and NH3 atmosphere before the growth of the hole transport layer 35. For this purpose, a nitrogen source gas and nitrogen gas can be supplied before the growth of a low-concentration doped layer 33b, while the supply of gallium source gas, magnesium source gas, and hydrogen gas is blocked. A procedure for changing the atmosphere of the chamber to a nitrogen and NH3 atmosphere can be carried out over 3 to 10 minutes.

[0058] After the hole transport layer 35 has grown, a p-type contact layer 37 is developed at a temperature of, for example, 910°C to 940°C. The p-type contact layer 37 is developed on the hole transport layer 35 by feeding the N source gas (for example, NH3), the Ga source gas (for example, TMGa or TEGa), the Mg source gas (for example, Cp2Mg), N2 gas, and H2 gas into the chamber. For example, the N2 source gas can be fed in at a flow rate of approximately 30 l / min to approximately 50 l / min, the H2 source gas at a flow rate of approximately 140 l / min to approximately 160 l / min, and the NH3 gas at a flow rate of approximately 30 l / min to approximately 50 l / min. More precisely, the flow rate ratio of N2:H2:NH3 can be 1:3:1, and the growth conditions of the p-type contact layer 37 can be the same as those for the hole injection layer 33, except for the flow rate of the Mg source gas.On the other hand, the flow rate of the Mg source gas is chosen so that a suitable dopant concentration is achieved, and the p-type contact layer 37 can achieve a Mg concentration of about 4E20 / cm. 3 or have more.

[0059] After the growth of the p-type contact layer 37, the temperature of the chamber can be reduced to about 700°C to about 800°C to perform a heat treatment of the p-type semiconductor layer 40 in an N2 atmosphere.

[0060] According to this exemplary embodiment, during the growth of the hole transport layer 35, the supply of H₂ gas is blocked to reduce the dopant concentration of the undoped layers 35a in the hole transport layer 35. Furthermore, N₂ gas and H₂ gas can be introduced during the growth of the hole injection layer 33 and the p-type contact layer 37 to prevent impairment of the crystal quality of the p-type semiconductor layer 40. Additionally, during the growth of the hole transport layer 35, the doped intermediate layer 35b is developed to increase the hole mobility from the p-type contact layer 37 to the hole transport layer 35.

[0061] Next, the electrodes contacting the n-type semiconductor layer 25 and the p-type semiconductor layer 40 are formed, and the resulting structure is divided into individual light-device chips, creating a lateral-type or semiconductor chip-type light-device. A support substrate (not shown) can then be formed on the p-type semiconductor layer 40, and the substrate 21 can be removed, resulting in a vertical-type light-device from which the growth substrate is removed.

[0062] Fig. Figure 4 is a diagram showing the power and forward voltage of lighting devices of an example according to the invention and of a comparative example, and Fig. Figure 5 is a diagram showing the resistance yield of the electrostatic discharge for an example according to the invention and a comparative example.

[0063] In this experiment, the light-emitting device of the inventive example was a lateral-type light-emitting device with a hole transport layer 35 including a doped intermediate layer 35b, and the light-emitting device of the comparison example was a lateral-type light-emitting device with a hole transport layer without the doped intermediate layer. In the inventive example and the comparison example, data from 40,000 light-emitting devices, each produced from separate wafers, were collected. Accordingly, the data in Fig. The 4 specified values ​​of power and forward voltage (Vf) are average values ​​of the lighting devices according to the examples according to the invention and average values ​​of the lighting devices according to the comparative examples. Fig. Figure 5 further shows the resistance yield of the electrostatic discharge as a ratio of non-failed lighting devices to all lighting devices after the electrostatic discharge test. That is, the electrostatic discharge yield shows a ratio of non-failed lighting devices to 40,000 lighting devices according to the inventive example and a ratio of non-failed lighting devices to 40,000 lighting devices according to the comparative example. In the electrostatic discharge test, a voltage of 3 kV was applied in HBM mode.

[0064] As in Fig. As shown in Figure 4, the luminaire of the inventive example exhibited lower forward voltage values ​​and higher luminous efficacy than the luminaires of the comparison example. This means that it can be seen that the luminaires of the inventive example, each having the doped intermediate layer 35b, have a higher luminous efficiency and allow for simpler recombination of holes and electrons than the luminaires of the comparison example, which do not have the doped intermediate layer. Furthermore, as shown in Figure 4, the luminaires of the inventive example exhibit lower forward voltage values ​​and higher luminous efficacy than the luminaires of the comparison example. Fig. Figure 5 shows that the lighting devices of the example according to the invention had higher resistance voltages of the electrostatic discharge than the lighting devices of the comparison example.

Claims

[1] A lighting device comprising: an n-type semiconductor layer (25); a p-type semiconductor layer (40); an active layer (29) arranged between the n-type semiconductor layer (25) and the p-type semiconductor layer (40); and an electron-blocking layer (31) located between the p-type semiconductor layer (40) and the active layer (29), where: the p-type semiconductor layer (40) comprises a hole injection layer (33), a p-type contact layer (37) and a hole transport layer (35) arranged between the hole injection layer (33) and the p-type contact layer (37), the hole transport layer (35) comprises several undoped layers (35a) and at least one doped intermediate layer (35b) between the undoped layers (35a), at least one of the undoped layers (35a) comprises a zone in which the hole concentration decreases with increasing distance to the hole injection layer (33) or the p-type contact layer (37), and the doped intermediate layer (35b) is arranged such that it overlaps at least partially with a region of the hole transport layer (35) in which the hole concentration of the hole transport layer (35) is 62% to 87% of the hole concentration of the p-type contact layer (37), and at least one of the undoped layers (35a) furthermore comprises a zone in which the hole concentration increases with decreasing distance to the doped intermediate layer (35b), wherein the zone in which the hole concentration increases with decreasing distance from the doped intermediate layer (35b) includes a region in which the hole concentration increases linearly. [2] Lighting device according to claim 1, wherein the hole injection layer (33) has a dopant concentration of 1E20 / cm² 3 up to 5E20 / cm 3 The p-type contact layer (37) has a dopant concentration of 4E20 / cm² 3 or more, and the doped intermediate layer (35b) has a dopant concentration of 1E18 / cm² 3 up to 1E20 / cm 3 has. [3] Lighting device according to claim 1 or 2, wherein the hole transport layer has a greater thickness than the total thickness of the hole injection layer (33) and the p-type contact layer (37). [4] Lighting device according to claim 3, wherein the doped intermediate layer (35b) has a thickness of 10 nm to 20 nm and the undoped layers (35a) have a thickness of 15 nm to 30 nm. [5] Lighting device according to one or more of claims 1 to 4, wherein the hole injection layer (33) borders the electron blocking layer (31). [6] Lighting device according to one or more of claims 1 to 5, wherein the zone in which the hole concentration decreases with increasing distance from the hole injection layer (33) or the p-type contact layer (37) comprises a region in which the hole concentration decreases linearly. [7] Lighting device according to one or more of claims 1 to 6, wherein the doped intermediate layer (35b) has a higher electrical resistance than the undoped layers (35a). [8] Method wherein a lighting device is manufactured according to any one of claims 1 to 7, including: Growth of the n-type semiconductor layer (25), the active layer (29), the electron blocking layer (31) and the p-type semiconductor layer (40) on a substrate within a chamber by means of metal-organic chemical vapor deposition, wherein the growth of the p-type semiconductor layer (40) comprises the following: Growth of the hole injection layer (33) on the substrate inside the chamber by feeding an N source gas, a Ga source gas, a Mg source gas, N2 gas and H2 gas into the chamber; Growth of the undoped layer (35a) on the hole injection layer (33) by feeding an N source gas, a Ga source gas and N2 gas into the chamber while simultaneously blocking the feeding of the Mg source gas and the H2 gas; Growth of the doped intermediate layer (35b) on the undoped layer (35a) by feeding an N source gas, a Ga source gas, N2 gas and an Mg source gas into the chamber; Growth of the undoped layer (35a) on the doped intermediate layer (35b) by supplying an N source gas, a Ga source gas and N2 gas into the chamber while simultaneously blocking the supply of the Mg source gas; and growth of the p-type contact layer (37) on the undoped layers (35a) by supplying an N source gas, a Ga source gas, a Mg source gas, N2 gas and H2 gas into the chamber. [9] Method according to claim 8, further comprising: the injection of an N source gas and N2 gas into the chamber while simultaneously blocking the injection of a Ga source gas, a Mg source gas and H2 gas to change the atmosphere of the chamber into an atmosphere of nitrogen and NH3 before the hole injection layer (33) is developed. [10] Method according to claim 8 or 9, wherein during the growth of the hole injection layer (33) and the p-type contact layer (37) a flow rate of H2 gas is higher than a flow rate of N2 gas. [11] Method according to claim 10, wherein during the growth of the hole injection layer (33) and the p-type contact layer (37) the flow rate of the H2 gas is three to five times higher than the flow rate of the N2 gas. [12] Method according to claim 11, wherein during the growth of the hole injection layer (33) and the p-type contact layer (37) the flow rate of the NH3 gas is lower than the flow rate of the H2 gas, and during the growth of the hole transport layer (35) the flow rate of the N2 gas is higher than the flow rate of the NH3 gas. [13] Method according to one or more of claims 8 to 12, wherein the hole injection layer (33) has a dopant concentration of 1E20 / cm² 3 up to 5E20 / cm 3The p-type contact layer (37) has a dopant concentration of 4E20 / cm² 3 or more and the doped intermediate layer (35b) has a dopant concentration of 1E18 / cm 3 up to 1E20 / cm 3 has.

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