KR20090062348A - Method of forming p-type nitride semiconductor layer and light emitting device having the same - Google Patents

Abstract

A method of forming a p-type nitride semiconductor layer doped with Mg using a metal organic chemical vapor deposition method is disclosed. The method loads a substrate into a reactor, feeds source gases including Ga source gas, N source gas, and Mg source gas into the reactor to grow a first Mg doped nitride semiconductor layer on the substrate, and The growth of the nitride semiconductor layer is stopped by supplying Ga source gas and Mg source gas supplied into the reactor, supplying NH ₃ gas, and supplying In source gas and NH ₃ gas into the reactor to form the first nitride. Doping In to the semiconductor layer. Thereby, the electrical conductivity and crystallinity of the p-type nitride semiconductor layer can be improved.

Description

A method of forming a nitride nitride semiconductor layer and a light emitting device having the same {METHOD OF FORMING P-TYPE NITRIDE SEMICONDUCTOR LAYER AND LIGHT EMITTING DEVICE HAVING THE SAME}

The present invention relates to a method of manufacturing a nitride-based light emitting device and a light emitting device, and more particularly to a method of forming a p-type nitride semiconductor layer and a light emitting device having 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.

On the other hand, the p-type nitride semiconductor layer is mainly formed using Mg as a dopant, where Mg is bonded with hydrogen to deteriorate the crystallinity of the p-type nitride semiconductor layer and does not contribute to the electrical conductivity of the p-type nitride semiconductor layer. You may not be able to. 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, there is a need for a method of forming a p-type nitride semiconductor layer capable of sufficiently increasing 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.

The problem to be solved by the present invention is to provide a method for forming a p-type nitride semiconductor layer with improved electrical conductivity and / or crystallinity.

The problem to be solved by the present invention is to provide a light emitting device having a p-type nitride semiconductor layer with improved electrical conductivity and / or crystallinity.

In order to solve the above problems, the present invention provides a method of forming a p-type nitride semiconductor layer doped with Mg.

A method of forming a p-type nitride semiconductor layer according to an aspect of the present invention includes loading a substrate into a reactor. Source gases including Ga source gas, N source gas, and Mg source gas are supplied into the reactor to grow a first Mg doped nitride semiconductor layer on the substrate. Subsequently, the supply of the Ga source gas and the Mg source gas supplied into the reactor is stopped to stop the growth of the nitride semiconductor layer. However, NH ₃ gas is supplied. Thereafter, In source gas and NH ₃ gas are supplied into the reactor, and In is doped into the first nitride semiconductor layer. In doped with the first nitride semiconductor layer reduces spontaneous compensation caused by Mg doping to improve electrical conductivity. In addition, the NH ₃ gas supplied after the growth of the first nitride semiconductor layer is stopped reduces the N vacancy in the nitride semiconductor layer by supplying a nitrogen source to the first nitride semiconductor layer.

According to an embodiment of the present invention, after In is doped, source gases including Ga source gas, N source gas, and Mg source gas are supplied into the reactor to supply a second Mg-doped nitride semiconductor on the substrate. The layer can be grown.

Stopping growth of the first nitride semiconductor layer and the In doping may prevent crystal defects, such as dislocations, formed in the first nitride semiconductor layer from growing into the second nitride semiconductor layer, and thus, nitride semiconductor. The crystallinity of the layer can be improved.

While growing the second Mg doped nitride semiconductor layer, the supply of the In source gas may be stopped.

In embodiments of the present invention, the first Mg doped nitride semiconductor layer and / or the second Mg doped nitride semiconductor layer may be a p-GaN layer.

In addition, the N source gas may include NH ₃ . The NH ₃ may be continuously supplied into the reactor during the growth of the first nitride semiconductor layer, the growth stop, and the In doping process. The NH ₃ may also be supplied continuously during the growth of the second nitride semiconductor layer.

The growth of the first Mg-doped nitride semiconductor layer, stop growth of the nitride semiconductor layer, and In doping may be repeated at least twice. As a result, a p-type nitride semiconductor layer having improved spontaneous crystallinity can be formed by reducing spontaneous compensation.

In order to solve the above problems, another aspect of the present invention provides a light emitting device having an Mg-doped p-type nitride semiconductor layer. The light emitting device includes a substrate, an n-type nitride semiconductor layer, a p-type nitride semiconductor layer doped with Mg and In, and an active layer interposed between the n-type nitride semiconductor layer and the p-type nitride semiconductor layer. In this case, In doped in the p-type nitride semiconductor layer has a concentration peak at the same height in the thickness direction of the p-type nitride semiconductor layer.

In some embodiments of the present invention, the concentration peak of In may appear at at least two height positions in the thickness direction of the p-type nitride semiconductor layer.

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

According to embodiments of the present invention, a nitride semiconductor grown by supplying an In source in an NH ₃ atmosphere and stopping supply of Ga and Mg sources in an NH ₃ atmosphere at a predetermined interval when the Mg-doped p-type nitride semiconductor layer is grown. By doping In to the layer, the spontaneous compensation caused by Mg doping can be reduced to improve electrical conductivity, and the crystal defect density such as dislocation density can be reduced to improve the crystallinity of the p-type nitride semiconductor layer. . Accordingly, a light emitting device having a low driving voltage and improved luminous efficiency and luminous output can be provided.

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, 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, and in the case of a multi quantum well structure, the quantum barrier layer and the quantum well layer may be alternately repeated two or more times and ten 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 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 and contains In therein. In is distributed uniformly so as to have a peak distribution at the same height in the thickness direction of the p-type nitride semiconductor layer 29, rather than uniformly distributed in the p-type nitride semiconductor layer 29. Based on the height of In having a peak distribution, the p-type nitride semiconductor layer may be divided into a first p-type nitride semiconductor layer 29a and a second p-type nitride semiconductor layer 29b. The first p-type nitride semiconductor layer 29a and the second p-type nitride semiconductor layer 29b may be nitride semiconductor layers having the same composition, but are not limited thereto and may have different compositions. In addition, in the p-type nitride semiconductor layer 29, there may be at least one height at which In has a peak distribution.

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 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 phase 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.

FIG. 2 is a flowchart illustrating a method of forming a p-type nitride semiconductor layer according to an embodiment of the present invention, and FIG. 3 illustrates a method of forming a p-type nitride semiconductor layer according to an embodiment of the present invention. Is a timing diagram.

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-based 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 Si source. Can be. 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.

In the active layer 27, an In _x Ga1 _{1- x} N (0.1 <x <1) quantum well layer and an In _y Ga _1-y N (0 <y <0.5) quantum barrier layer are twice or more times in a nitrogen atmosphere. It may be formed as a multi-quantum well structure repeated below. Preferably, each quantum well layer may be formed of 1 ~ 4nm thickness and In content (0.1 <x <0.4), each quantum barrier layer is formed of 5 ~ 20nm thickness and In content (0 <y <0.2) Can be.

2 and 3, the Ga source, the N source gas, and the Mg source gases are supplied into the reactor to grow the first Mg-doped p-type nitride semiconductor layer 29a (S03). The supply of source gases is done for T1 time.

Trimethylgallium (TMGa) or triethylgallium (TEGa) may be used as the Ga source, and ammonia (NH ₃ ) or dimethylhydrazine (DMHy) may be used as the N source gas, and CP ₂ Mg or DMZn may be used as the Mg source. Can be used. The Mg doping concentration in the first p-type nitride semiconductor layer 29a may be in the range of 3 to 8 × 10 ¹⁷ / cm 3, and may be formed to a thickness of 5-50 nm. The T1 time is set to the time required to form the first p-type nitride semiconductor layer of the required thickness.

Thereafter, the supply of the Ga source gas and the Mg source gas supplied into the reactor is stopped to stop the growth of the nitride semiconductor 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, most of the Ga source gas and the Mg source gas remaining in the reactor are discharged to the outside. The T2 time may be 1 to 60 seconds as a time for discharging the Ga source gas and the Mg 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 Ga source gas and the Mg 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, In source gas and NH ₃ gas are supplied into the reactor to dope In into the first nitride semiconductor layer (S07). The In doping is performed for a time T3, T3 may be in the range of 1 to 60 seconds.

When growing the nitride semiconductor layers using MOCVD, the n-type nitride semiconductor layer 25, the active layer 27 and the p-type nitride semiconductor layer 29 can be grown in the same reactor. Therefore, the flow rate of the In source is preferably in the process stability of the flow rate of the In source used in the growth of the active layer 27.

After In is doped, the second Mg-doped p-type nitride semiconductor layer 29b is grown by supplying Ga source gas, N source gas, and Mg source gas into the reactor (S09). The second nitride semiconductor layer 29b may be grown for a time T4, and T4 may be the same as T1, but is not limited thereto. In addition, the second nitride semiconductor layer 29b may be grown in the same composition as the first nitride semiconductor layer 29a, but is not limited thereto.

Meanwhile, while growing the second nitride semiconductor layer 29b, the supply of the In source gas may be stopped. In this case, after a predetermined time elapses after the In source gas is stopped, the second nitride semiconductor layer 29b may be grown.

In the present embodiment, although the p-type nitride semiconductor layer 29 is formed and described by the first nitride semiconductor layer 29a and the second nitride semiconductor layer 29b, growth of the nitride semiconductor layer, growth stop, In doping steps may be repeated several times. In this case, each of the grown p-type nitride semiconductor layers may be formed to a thickness of 5-50nm, the entire p-type nitride semiconductor layer may be formed to have a thickness of 0.1-5um.

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, self-compensation is reduced by stopping growth during the growth of the Mg-doped p-type nitride semiconductor layer 29, supplying NH3 gas and also doping In. The electrical conductivity of the type nitride semiconductor layer 29 can be improved. In addition, by doping In during the growth of the p-type nitride semiconductor layer 29, it is possible to prevent the potential from growing in the nitride semiconductor layer grown thereon, thereby improving the crystallinity of the p-type nitride semiconductor layer 29.

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.

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

2 is a flowchart illustrating a method of forming a p-type nitride semiconductor layer according to an embodiment of the present invention.

3 is a timing diagram illustrating a method of forming a p-type nitride semiconductor layer according to an embodiment of the present invention.

Claims (9)

In the method of forming a p-type nitride semiconductor layer doped with Mg, Load the substrate into the reactor, Supplying source gases including Ga source gas, N source gas, and Mg source gas into the reactor to grow a first Mg doped nitride semiconductor layer on the substrate, To stop the growth of the nitride semiconductor layer by stopping the supply of Ga source gas and Mg source gas supplied into the reactor, supplying NH ₃ gas, A method of forming a p-type nitride semiconductor layer comprising supplying In source gas and NH ₃ gas into the reactor and doping In to the first nitride semiconductor layer. The method according to claim 1, After the In doped, p-type comprising supplying source gases including Ga source gas, N source gas, and Mg source gas into the reactor to grow a second Mg doped nitride semiconductor layer on the substrate. Nitride semiconductor layer formation method. The method according to claim 2, While growing the second Mg doped nitride semiconductor layer, the supply of In source gas is stopped. The method according to claim 2, And the first Mg doped nitride semiconductor layer and the second Mg doped nitride semiconductor layer are p-GaN layers. The method according to claim 1, And the N source gas comprises NH ₃ . The method according to claim 1, Growing the first Mg doped nitride semiconductor layer, stopping growth of the nitride semiconductor layer, and repeating the In doping steps at least twice. Board; an n-type nitride semiconductor layer; A p-type nitride semiconductor layer doped with Mg and In; And An active layer interposed between the n-type nitride semiconductor layer and the p-type nitride semiconductor layer, And In which is doped in the p-type nitride semiconductor layer is distributed to have a concentration peak at the same height in the thickness direction of the p-type nitride semiconductor layer. The method according to claim 7, Wherein the concentration peak of In appears at at least two height positions in the thickness direction of the p-type nitride semiconductor layer. The method according to claim 7, The p-type nitride semiconductor layer is GaN.

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