KR20060062418A - Method for fabricating iii-v nitride compound semiconductor ultraviolet light-emitting device - Google Patents

Abstract

A method for manufacturing a III-V nitride semiconductor ultraviolet light emitting device is disclosed. In the present invention, the absorption of ultraviolet light from the p-type upper contact layer is minimized when the ultraviolet light is emitted by the electric field, and the loss of transition from the conduction band of the single or multi-quantum well structure to the acceptor level of the p-type upper contact layer is reduced. In order to minimize, the amount of the p-type dopant is increased as the p-type upper contact layer growth process proceeds. According to the present invention, it is possible to minimize the absorption of light in the p-type gallium nitride contact layer, and to minimize the loss of transition from the conduction band of the multi-quantum well to the acceptor level in the p-type gallium nitride contact layer, high efficiency ultraviolet light emitting device Can be produced.

UV light emitting device, multi-quantum well structure, p-type upper contact layer, dopant

Description

Method for fabricating III-V nitride compound semiconductor ultraviolet light-emitting device             

1 is a schematic view showing a conventional conventional nitride ultraviolet semiconductor light emitting device;

2 is a graph measuring the intensity of light emission according to the p-type gallium nitride contact layer thickness;

Figure 3 is a graph measuring the intensity of luminescence according to the temperature in the case of the conventional case of uniformly doped with magnesium and the case of the present invention;

Figure 4 is a graph measuring the intensity of light emission for each wavelength in the case of the conventional doped with magnesium uniformly and in the case of the present invention; And

Figure 5 is a graph measuring the intensity of light emission for each input current in the case of the conventional doping and uniformly doped with magnesium.

The present invention relates to a method of manufacturing a III-V nitride semiconductor ultraviolet light emitting device, and more particularly, to a method of manufacturing a III-V nitride semiconductor semiconductor light emitting device in which a p-type upper contact layer is formed while increasing the amount of dopant. .

Recently, much attention has been paid to high-brightness white light emitting devices using nitride semiconductors and their economic value is also great.

 There are three ways to implement a high brightness white light emitting device.

First, a method of implementing white by combining three light emitting devices emitting three primary colors of red, green, and blue. In order to make a single white high luminance light emitting device by this method, a technique of individually controlling light emission characteristics such as temperature life and device life of three color light emitting devices must be preceded, which makes it difficult to implement a white light source.

Second, white is achieved by exciting a yellow phosphor using a blue light emitting device as a light source. When using this method, the luminous efficiency is excellent, the color rendering index (CRI) is low, and the color rendering index changes according to the current density. Therefore, there is a problem in obtaining a white high luminance light emitting device close to sunlight. .

Lastly, a white light is generated by exciting three primary color phosphors by using an ultraviolet light emitting diode (LED) as a light source. This method is most feasible because it has excellent luminescence properties and color rendering index properties, so that a high brightness white light emitting device close to sunlight can be realized. At this time, the problem of increasing the efficiency of the ultraviolet light emitting element is considered to be the most important problem.

1 is a schematic view showing a conventional conventional nitride ultraviolet semiconductor light emitting device.

Referring to FIG. 1, the buffer layer 20, the undoped intermediate layer 30, the uniformly doped n-type contact layer 40, the n-type cladding layer 50, the active layer, and the p-type cladding are formed on the substrate 10. The layer 70 and the p-type contact layer 80 are sequentially stacked. In this case, the n-type contact layer 40 is made of GaN, the n-type cladding layer 50 is made of Al _x Ga _1-x N (0≤x≤1), the active layer is Ga _1-xy In _x Al _y well layer of the N (0≤x, y≤1, x + y <1) of the barrier layer 61 and a _{Ga 1-xy in x Al y} N (0≤x, y≤1, x + y <1) It consists of 62. The p-type cladding layer 70 is made of Al _x Ga _1-x N (0 ≦ _x ≦ 1) and the p-type contact layer 80 is made of GaN. At this time, the n-type cladding layer 50 and the p-type cladding layer 70 made of Al _x Ga _1-x N (0 ≦ _x ≦ 1) may be omitted. In addition, the n-type cladding layer 50 and the p-type cladding layer 70 made of AlGaN may use a superlattice layer made of GaN and Al _x Ga _1-x N (0 ≦ _x ≦ 1). As the substrate, GaN, SiC, GaAs, Si, ZnO and the like can be used. Generally, sapphire is mainly used because the GaN thin film grown on sapphire has good crystallinity and is economical.

In this case, in order to improve electrical characteristics in a multi-quantum well structure of a general light emitting device, a p-type gallium nitride contact layer 80 having a high hole concentration is essential. In general, in the multi-quantum well structure of the ultraviolet light emitting device, a hole concentration of 10 ¹⁸ or more is required for good electrical characteristics, and the energy level due to the deep donor and acceptor is about 2.8 to 2.6 eV. Considering that the energy of light generated in the multi-quantum well structure of the ultraviolet light emitting device is 3eV or more, this is caused by the deep level donor and acceptor when the light generated in the multi-quantum well structure is emitted through the p-type gallium nitride contact layer. It means that the absorption of light occurs by the level.

In addition, in the p-type gallium nitride contact layer having a hole concentration of 10 ¹⁸ or more, the acceptor level is generally higher than the valence band of the multi-quantum well structure that emits ultraviolet light. Therefore, light is generated by the recombination of electrons and holes in the multi-quantum well structure. At this time, since the acceptor level is higher than the valence band of the multi-quantum well structure, the light is recombined with the acceptor level before recombination of some electrons and holes. This phenomenon also reduces the luminous efficiency of ultraviolet light.

Therefore, the technical problem to be achieved by the present invention is to improve the luminous efficiency by reducing the transition to the acceptor level in the p-type gallium nitride contact layer and the absorption of light in the p-type gallium nitride contact layer in the conduction band of the multi-quantum well structure. The present invention provides a method of manufacturing a III-V nitride semiconductor ultraviolet light emitting device.

In order to achieve the above technical problem, a method of manufacturing a III-V nitride semiconductor ultraviolet light emitting device according to the present invention includes: a lower contact layer including n-type Al _x Ga _y In _Z N (0 ≦ x, y, z ≦ 1) And an upper contact layer composed of p-type Al _x Ga _y In _Z N (0≤x, y, z≤1), the Al _x Ga _y In _Z N (0≤x, y, z≤1) barrier In the manufacturing method of III-V nitride-based ultraviolet light-emitting device comprising a layer and an active layer consisting of a single or multi-quantum well structure of Al _x Ga _y In _Z N (0≤x, y, z≤1) well layer,

When the ultraviolet light is emitted by an electric field, absorption of the ultraviolet light in the p-type upper contact layer is minimized and loss of transition from the conduction band of the single or multi-quantum well structure to the acceptor level of the p-type upper contact layer is minimized. Preferably, as the p-type upper contact layer growth process proceeds, the amount of the p-type dopant is increased.

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

Since the III-V nitride based ultraviolet light emitting device according to the embodiment of the present invention and the light emitting device shown in the prior art have the same structure, a manufacturing method according to the embodiment of the present invention will be described in detail with reference to FIG. 1.

Referring to FIG. 1, first, 10000 sccm of hydrogen gas is introduced into a growth apparatus at a high temperature of 1030 ° C. or more for 10 minutes to remove organic substances remaining on the sapphire (0001) surface used as the substrate 10. Then, trimethylgallium at a flow rate of 94 micromoles / minute and ammonia are introduced at a flow rate of 13000 sccm, respectively, and a 25 nm thick gallium nitride (GaN) buffer layer 20 is grown on the substrate 10 for 0.9 minutes. The process temperature at this time is 550 degreeC, and time is 0.9 minutes.

Next, trimethylgallium at a flow rate of 105.5 micromol / min and ammonia at a flow rate of 7600 sccm were respectively introduced to grow the undoped intermediate layer 30 on the gallium nitride (GaN) buffer layer 20 to a thickness of 2 to 3 µm. Let's do it. The process temperature at this time is 1020 degreeC, and a growth time is 1 hour.

Next, an n-type gallium nitride contact layer 40 having a thickness of 1 to 2 mu m is formed. At this time, silicon tetrahydride (SiH ₄ ) diluted to 10% by volume in hydrogen gas as a dopant is flowed at a flow rate of 10 to 30 sccm. This corresponds to a hall measurement concentration of 3 x ^{10 18 to 7} x 10 ¹⁸ / cm ³ of n-type gallium nitride.

In the light emitting device of this embodiment, a structure in which the n-type cladding layer and the p-type cladding layer were omitted was used. In addition, the n-type cladding layer and the p-type cladding layer are omitted in the conventional light emitting device to be compared with the present embodiment.

Subsequently, trimethylgallium at a flow rate of 25.4 micromoles / minute and ammonia at a flow rate of 4400 sccm are respectively introduced to grow a gallium nitride (GaN) barrier layer 61 on the n-type gallium nitride contact layer 40.

Subsequently, trimethylgallium at a flow rate of 10.8 micromoles / minute, trimethylindium at a flow rate of 11.08 micromoles / minute, and ammonia at a flow rate of 4400 sccm were respectively introduced to indium nitride (InGaN) having a thickness of 2 nm on the barrier layer 61. The well layer 62 is grown. At this time, the process temperature is 800 ° C.

The barrier layer 61 is formed again on the well layer 62.

In this embodiment, the barrier layer and the well layer are repeated five times.

And a p-type gallium nitride contact layer having a thickness of 0.1 μm on the multi-quantum well structure by introducing trimethyl gallium at a flow rate of 105.5 micromol / min, ammonia at a flow rate of 7600 smm, and bicyclocyclodienyl magnesium; 80) is grown using organometallic chemical vapor deposition or molecular beam epitaxy. At this time, the process time is 5 minutes, and the amount of bicyclocyclodienyl magnesium is increased linearly or stepwise from 0 to 0.35 micromoles per minute. On the other hand, the amount of bicyclocyclodienyl magnesium may be increased exponentially or discontinuously.

2 is a graph measuring the intensity of light emission according to the p-type gallium nitride contact layer thickness.

Referring to FIG. 2, it can be seen that the emission wavelength is 385 nm and is an ultraviolet region. In addition, while the thickness of the p-type gallium nitride contact layer was reduced from 0.25 μm to 0.1 μm, the intensity of light generated in the multi-quantum well structure increased significantly. When the thickness of the p-type gallium nitride contact layer became 0.1 μm, the wavelength was 385 nm. It can be seen that the peak in the ultraviolet region is significant. This is because as the thickness of the p-type gallium nitride contact layer decreases, absorption of light is significantly reduced by the energy band formed by the deep level donor and acceptor energy level in the p-type gallium nitride contact layer. That is, the deep level donor and acceptor energy level in the p-type gallium nitride contact layer act as an absorbing layer of light generated in the multi-quantum well structure. As shown in the present invention, the p-type gallium nitride contact is gradually increased while increasing the amount of dopant. Growing a layer can reduce the absorption of light.

Figure 3 is a graph measuring the intensity of luminescence according to the temperature in the case of the conventional case of uniformly doped with magnesium and the case of the present invention.

Referring to FIG. 3, in the conventional case, when the temperature is raised, electrons or holes that are bound to the well layer are released from the well layer by thermal energy, and thus the light intensity decreases. However, in the case of the present invention, it can be seen that the reduction is smaller than that of the conventional case. This is because, in the multi-quantum well structure, the amount of escaped from the well layer by the thermal energy is the same, and as described above, the phenomenon in which the transition from the conduction band of the multi-quantum well structure to the acceptor level in the p-type gallium nitride contact layer occurs. In case of, the reduction is proved.

Figure 4 is a graph measuring the intensity of light emission for each wavelength in the case of the conventional doping of magnesium uniformly and in the case of the present invention.

Referring to FIG. 4, it can be seen that yellow light emission of 600 nm wavelength, which is known to be caused by a defect in gallium nitride, is generally larger than that of the light emitting device according to the present invention.

Figure 5 is a graph measuring the intensity of light emission for each input current in the case of the conventional doping and uniformly doped with magnesium.

Referring to FIG. 5, it can be seen that when the same current is input, the intensity of light emission is greater than in the case of the present invention. That is, in the case of the present invention, it can be seen that the light extraction efficiency is greatly increased than the conventional case.

According to the method of manufacturing the III-V nitride semiconductor ultraviolet light emitting device according to the present invention as described above, the absorption of light can be minimized by using a method of doping with increasing dopant during growth of the p-type gallium nitride contact layer. In this case, a highly efficient ultraviolet light emitting device can be fabricated by minimizing the loss transition from the conduction band of the multi-quantum well to the acceptor level in the p-type gallium nitride contact layer.

The present invention is not limited to the above embodiments, and it is apparent that many modifications are possible by those skilled in the art within the technical spirit of the present invention.

Claims (9)

a bottom contact layer consisting of n-type Al _x Ga _y In _Z N (0≤x, y, z≤1) and a top contact consisting of p-type Al _x Ga _y In _Z N (0≤x, y, z≤1) doedoe interposed between the _{layer, Al x Ga y in Z N} (0≤x, y, z≤1) barrier layer and the _{Al x Ga y in Z N (} 0≤x, y, z≤1) a single well layer, or In the manufacturing method of III-V nitride-based ultraviolet light-emitting device comprising an active layer consisting of a multi-quantum well structure, When the ultraviolet light is emitted by an electric field, absorption of the ultraviolet light in the p-type upper contact layer is minimized and loss of transition from the conduction band of the single or multi-quantum well structure to the acceptor level of the p-type upper contact layer is minimized. The method of manufacturing a III-V nitride semiconductor UV light emitting device according to claim 1, wherein the amount of the p-type dopant is increased as the p-type upper contact layer growth process is performed. The method of claim 1, wherein the p-type upper contact layer is grown using an organometallic chemical vapor deposition method or molecular beam epitaxy. The method of manufacturing a III-V nitride semiconductor UV light emitting device according to claim 1, wherein the upper contact layer has a thickness of 0.1 to 0.3 µm. The method of claim 1, wherein the dopant is bicyclocyclodienyl magnesium. The method of manufacturing a III-V nitride based semiconductor ultraviolet light emitting device according to claim 1, wherein the amount of the dopant is linearly increased. The method of manufacturing a III-V nitride semiconductor ultraviolet light emitting device according to claim 1, wherein the amount of the dopant is increased stepwise. The method of claim 1, wherein the amount of the dopant is exponentially increased. The method of claim 1, wherein the amount of the dopant is discontinuously increased. The method of claim 5, wherein when the p-type upper contact layer is grown to a thickness of 0.1 μm for 5 minutes, the amount of dopant is increased from 0 to 0.35 micromoles per minute. A method of manufacturing a III-V nitride semiconductor ultraviolet light emitting device.

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