KR20050024078A - Method to Make Light Emitting Devices using p-ZnO - Google Patents

Abstract

PURPOSE: A method of manufacturing a ZnO short wavelength light emitting device is provided to acquire stable electrical properties by forming a P type ZnO thin film using a sputtering process instead of a growth process. CONSTITUTION: An N type ZnO thin film(102) is grown on a base substrate(101). A P type ZnO thin film(103) is deposited on the N type ZnO thin film by using sputtering. A heat treatment is performed on the resultant structure to activate the P type ZnO thin film. An electrode(104) is formed on the N type ZnO thin film and the P type ZnO thin film, simultaneously.

Description

Manufacture method of zinc oxide short wavelength light emitting device using ｐ type zinc oxide semiconductor {Method to Make Light Emitting Devices using p-ZnO}

The present invention relates to a method of forming a p-type zinc oxide on a zinc oxide thin film and a fabrication technique for a pn-bonded thin film, and more particularly, by depositing an n-type zinc oxide thin film on a base substrate using a sputtering method, After forming a p-type zinc oxide thin film doped with P), the present invention relates to a method for manufacturing a zinc oxide light emitting device having improved structural and electrical properties through heat treatment.

Light emitting diodes (LEDs) and laser diodes (LDs), which spontaneously emit light under forward bias conditions, have been used in the field of visual display, optical data storage, and optical fiber communication. As information usage in the field of information and communication expands exponentially, optical devices in the short wavelength range are needed to store more information.In the display industry, as one of the major industries, the energy consumption rate and light efficiency are high. Interest has increased, and as a result, interest in LEDs has exploded. The use of green and blue LEDs is becoming more common due to the development of p-type gallium nitride-based semiconductors, and efforts have been made to develop short-wavelength light emitting devices in the ultraviolet region, but there are still no clear achievements.

Gallium nitride-based semiconductors have disadvantages of difficulty in crystal growth and high device resistance that are made at high temperature (1000 ° C. or more). In particular, in the case of a p-type gallium nitride-based semiconductor, since the surface of the thin film is not good and the carrier density is low, there is a great difficulty in manufacturing a gallium nitride-based semiconductor device. For this reason, there is no current progress in optical device technology in the short wavelength region using gallium nitride-based semiconductors.

As a result, efforts are being made to find new short wavelength light emitting materials. Among them, zinc oxide (ZnO) is attracting attention as a representative material to replace gallium nitride-based semiconductors.

Zinc oxide, which has a very similar crystal structure and band gap to gallium nitride, has an exciton binding energy that is about three times higher than that of gallium nitride, and thus uses an optical device having high luminous efficiency using excitons which can be stably existed at room temperature and high temperature. I can make it.

In addition, it is considered a material that is likely to replace gallium nitride because of the advantages of the manufacturing method that can produce a high quality thin film at a relatively low temperature.

However, in spite of these advantages, zinc oxide is known to be very difficult to be a p-type material by nature, and very rare cases of overcoming the p-type material, and its electrical characteristics are also very unstable.

There are several groups that recently reported the development of p-type zinc oxide thin films using arsenic (As) and nitrogen (N) (Journal of Crystal Growth 219 (2000) 330, Applied Physics Letter 79 (2001) 4139, Applied Physics Letter) 80 (2002) 1195, Applied Physics Letter 81 (2002) 1830,).

And, there are examples of zinc oxide pn junctions (Journal of Crystal Growth 219 (2000) 419, Applied Physics Letter 76 (2000) 3257, Jpn. J. Appl. Physics Letter 40 (2001) L177). Its characteristics and efficiency are very low, making it impossible to manufacture a real device.

Thus, in order to overcome the difficulties in manufacturing the p-type zinc oxide thin film, a heterojunction light emitting device made by growing an n-type zinc oxide thin film on a p-type gallium nitride or p-type strontium oxide thin film instead of p-type zinc oxide Attempts have also been made to develop.

Among the prior arts for developing p-type zinc oxide and developing light emitting devices using the same, arsenic (As) is used as a p-type dopant by MBE (molecular beam epitaxy) method (US Patent. 2001. US 6410162B1, White et al. However, the electrical characteristics of the device fabricated through this method (IV curve) are similar to those of the diode, but the leakage current due to the defects of the thin films is so large that the electrical characteristics of the device are affected by the ohmic characteristics. It's close. In addition, this method is disadvantageous in that the manufacturing time is long, it is uneconomical by using expensive equipment, and the large area growth of the thin film is difficult.

'Method for manufacturing short wavelength zinc oxide light emitting device according to deposition temperature' (Special 2001-0070677. Lee Sang-yeol et al.) And 'Method for manufacturing short wavelength zinc oxide light emitting device for post-heat treatment' (Special 2001-0068017. ) Uses a zinc oxide (sapphire) substrate, which is an insulator, as a p-type semiconductor, and if this is possible, a method of manufacturing a p-type sapphire should be suggested, but it cannot be considered as practical.

In addition, since the current-voltage curve (I-V curve) obtained when the device is manufactured is not presented, the possibility of manufacturing the short wavelength light emitting device proposed by this patent may be doubted.

In 2002, Nikishigeru devised the ZnO compound semiconductor light emitting device and its manufacturing method (Special 2002-0048377), although there is a method of growing a high quality zinc oxide thin film and the structure of the light emitting device. There was no mention of the results of measuring the optical and electrical properties of the method and the zinc oxide light emitting device.

As such, there is no current p-type zinc oxide semiconductor manufacturing technology and device manufacturing technology with reproducibility and reliability.

In 2003, the development of p-type zinc oxide semiconductor with reproducibility and reliability using sputtering method was published in American Journal of Applied Physics Letters, 83 (2003) 62. It's happening.

An object of the present invention is to manufacture a p-type zinc oxide semiconductor showing a stable electrical characteristics by using a sputtering method, instead of the p-type zinc oxide semiconductor growth method of the conventional electrical characteristics are very unstable and poor reproducibility, The present invention provides a technique for making a zinc oxide short wavelength light emitting device.

In order to achieve the above object, the light emitting device fabrication method comprises the steps of growing an n-type zinc oxide thin film on the base substrate, a p-type zinc oxide thin film on the n-type zinc oxide thin film, and the p-type Activating the zinc oxide thin film by heat treatment, and forming an electrode on the n-type zinc oxide thin film and the p-type zinc oxide thin film.

Another light emitting device manufacturing method of the present invention comprises the steps of growing an n-type gallium nitride thin film on the base substrate, a p-type zinc oxide thin film on the n-type gallium nitride thin film and the p-type zinc oxide thin film Activating by heat treatment, and forming an electrode on the n-type zinc oxide thin film and the p-type zinc oxide thin film.

Another light emitting device manufacturing method of the present invention comprises the steps of growing a p-type zinc oxide thin film on the zinc oxide substrate, the step of thermally activating the p-type zinc oxide thin film, and the top of the zinc oxide substrate and the p-type zinc oxide thin film Forming an electrode in the.

Another light emitting device fabrication method of the present invention comprises the steps of growing an n-type zinc oxide thin film on the base substrate, and sequentially growing a p-type gallium nitride thin film and a p-type zinc oxide thin film on the n-type zinc oxide thin film; And thermally activating the p-type zinc oxide thin film, and forming an electrode on the n-type zinc oxide thin film and the p-type zinc oxide thin film.

Another light emitting device fabrication method of the present invention comprises the steps of growing an n-type gallium nitride thin film on the base substrate, and sequentially growing a p-type gallium nitride thin film and a p-type zinc oxide thin film on the n-type gallium nitride thin film; And activating the p-type zinc oxide thin film by heat treatment, and forming an electrode on the n-type gallium nitride thin film and the p-type zinc oxide thin film.

Another light emitting device fabrication method of the present invention comprises the steps of sequentially growing a p-type zinc nitride thin film and a p-type zinc oxide thin film on the zinc oxide substrate, the step of heat treatment to activate the p-type zinc oxide thin film, and zinc oxide substrate And forming an electrode on the top and the p-type zinc oxide thin film.

In the present invention, the base substrate preferably includes at least one element or compound selected from aluminum oxide (sapphire), silicon (Si), gallium arsenide (GaAs), silicon carbide (SiC), and zinc oxide (ZnO). .

In the present invention, the dopant material used for depositing the n-type zinc oxide thin film is preferably made of at least one element selected from aluminum (Al), gallium (Ga), and indium (In).

The dopant material used to deposit the p-type zinc oxide thin film in the present invention is phosphorus (P), rhenium (Re), lithium (Li), sodium (Na) potassium (K), cesium (Cs), antimony (Sb) ) And one or more elements selected from lead (Pb).

Between the step of depositing the n-type zinc oxide thin film and the step of depositing a p-type zinc oxide thin film in the present invention, the step of depositing a zinc oxide thin film doped with a photoluminescent active layer on the n-type zinc oxide thin film It includes more.

In the present invention, between depositing the n-type zinc oxide thin film and depositing the p-type zinc oxide thin film, gallium nitride containing indium (In) or aluminum (Al) on the n-type zinc oxide thin film ( And depositing a single or multiple quantum well layer comprising at least one compound selected from GaN), gallium nitride (GaN), zinc magnesium oxide (ZnMgO), and zinc cadmium oxide (ZnCdO) containing no impurities. May be included.

In the present invention, the heat treatment is preferably made for 1 to 1000 seconds at 300 ~ 1500 ℃.

In the present invention, the thickness of the thin film layer is preferably 1 to 1,000 nm.

Hereinafter, the present invention will be described in more detail with reference to the accompanying surface.

1 is a view showing the structure of a zinc oxide light emitting device according to an embodiment of the present invention.

In the above embodiment, the light emitting device includes a substrate layer, an n-type zinc oxide layer, a p-type zinc oxide layer, and an electrode layer.

2 is a flowchart illustrating a manufacturing process of a light emitting device according to an embodiment of the present invention.

Referring to FIG. 2, the light emitting device fabrication process includes growing an n-type zinc oxide thin film on a base substrate to a thickness of about 0.5 to 2 μm at 200 to 1000 ° C., and about 0.3 to 20 μm at 200 to 1000 ° C. Growing p-type zinc oxide thin film doped with phosphorus (P) to the upper layer, heat-treating for 1 to 3 minutes at 300 to 1000 ° C or higher, and n-type zinc oxide layer and p-type zinc oxide layer, respectively. Forming an electrode.

3 is a measurement result showing a change in current value (I-V curve) according to the voltage of a short wavelength zinc oxide light emitting device manufactured according to an embodiment of the present invention.

Referring to FIG. 3, this shows a change in current value according to a change in voltage of a short wavelength zinc oxide light emitting device manufactured by the method according to the present invention, and is a typical diode unlike the shape of a current-voltage curve of conventional diodes. Show the characteristics well.

Hereinafter, the present invention will be described in more detail with reference to preferred embodiments. However, this embodiment is only presented to understand the content of the present invention and should not be construed that the scope of the present invention is limited to these embodiments.

< Example>

4 is a schematic diagram of a sputtering method apparatus used in the present invention. The sputtering apparatus has a plurality of targets (2, 3 and 4 in FIG. 4) capable of depositing a multilayer thin film in a chamber filled with vacuum or reactive gas, and can control the distance between the target holder and the substrate (5 in FIG. 4). have.

The pressure inside the sputter chamber is 10mTorr ~ 20mTorr, while maintaining the ratio of argon and oxygen at 1: 1 ~ 3: 1, while maintaining the temperature of the base substrate at 200 ~ 1200 ℃, the n-type zinc oxide thin film is changed to AC power 60 Supply ~ 150W to deposit. At this time, when the AC power is not sufficiently supplied or excessively high, a thin film of good quality cannot be formed.

The target used to make the n-type zinc oxide thin film is a mixture of zinc oxide and Al ₂ O ₃ , Ga ₂ O ₃ , In ₂ O ₃ in a mass ratio of 97: 3 ~ 99.9: 0.1. The higher the mass ratio of the dopant materials, the worse the characteristics of the thin film, and less than the suggested amount has a disadvantage that the amount of the dopant is not supplied enough.

While maintaining a constant pressure inside the sputter reactor, the AC power is maintained between 60-150W, the temperature between 200-1000 ° C, and a phosphorus (P) -doped p-type zinc oxide thin film is deposited on the thin film layer. Silver zinc oxide is mixed with P ₂ O ₅ , P, Zn ₂ P ₂ O ₇ and Zn ₃ P ₂ in a mass ratio of 97: 3 to 99.9: 0.1.

The produced device is heat-treated for 1 to 3 minutes in a temperature of 300 ~ 1000 ℃, nitrogen and air atmosphere. As a result, the zinc oxide thin film doped with P becomes electrically p-type due to the activation of phosphorus (P), and the hole concentration is about 1 x 10 ¹⁸ to 1.7 x 10 ¹⁹ cm ^-3 , and the hole mobility is about 0.5. It becomes -3.5 cm <2> / V * s. In addition, the electron concentration of the n-type zinc oxide layer formed on the sapphire is also about 1 x 10 ¹⁸ -1 x 10 ²¹ cm ^-3 , and the electron mobility is about 1-100 cm 2 / Vs. When the heat treatment method is used, the crystallinity of the thin film is also greatly improved, and thus the efficiency of the light emitting device can be increased because non-emitting center defects are reduced.

As described above, according to the present invention, a p-type zinc oxide thin film which can stably exist even at high temperature for a long time can be economically manufactured by sputtering method, and the operation time is long and the electrical property is stable based on this. And, there is an advantage that can be produced a short wavelength light emitting device excellent in light efficiency.

      As described above, although described with reference to a preferred embodiment of the present invention, those skilled in the art will be variously modified and modified within the scope of the present invention without departing from the spirit and scope of the present invention described in the claims below. It will be appreciated that it can be changed.

1 is a cross-sectional view illustrating a structure of a p-n junction layer mainly composed of zinc oxide on a base substrate of a short wavelength ZnO light emitting device according to an exemplary embodiment of the present invention.

2 is a flowchart illustrating a manufacturing process of a short wavelength zinc oxide light emitting device according to an exemplary embodiment of the present invention.

3 is a measurement result showing a change in the current value (I-V curve) according to the voltage of the short wavelength zinc oxide light emitting device according to the embodiment of the present invention.

4 is a schematic diagram of a sputtering apparatus used in the present invention.

{Description of major symbols in the drawing}

101: base substrate 102: n-type zinc oxide

103: p-type zinc oxide 104: electrode

Claims (20)

In the formation of a junction light emitting diode, growing an n-type zinc oxide thin film on the base substrate, growing a p-type zinc oxide thin film on the n-type zinc oxide thin film, heat treatment of the p-type zinc oxide thin film is activated And forming an electrode on the n-type zinc oxide thin film and the p-type zinc oxide thin film. In forming a junction light emitting diode, growing an n-type gallium nitride thin film on the base substrate, growing a p-type zinc oxide thin film on the n-type gallium nitride thin film, heat treatment of the p-type zinc oxide thin film is activated And forming an electrode on the n-type zinc oxide thin film and the p-type zinc oxide thin film. The base substrate of claim 1, wherein the base substrate includes one or more elements or compounds selected from aluminum oxide (sapphire), silicon (Si), gallium arsenide (GaAs), silicon carbide (SiC), and zinc oxide (ZnO). Light emitting device manufacturing method characterized in that. The light emitting device of claim 1, wherein the dopant material used for depositing the n-type zinc oxide thin film includes at least one element selected from aluminum (Al), gallium (Ga), and indium (In). How to make. The dopant material used for depositing a p-type zinc oxide thin film is a phosphorus (P), rhenium (Re), lithium (Li), sodium (Na) potassium (K), cesium (Cs), anti A light emitting device manufacturing method comprising at least one element selected from moni (Sb) and lead (Pb). 2. The zinc oxide thin film of claim 1, further comprising depositing an undoped zinc oxide thin film on the n-type zinc oxide thin film between the depositing the n-type zinc oxide thin film and the p-type zinc oxide thin film. Light emitting device manufacturing method characterized in that it further comprises a step. According to claim 1, Between the step of depositing the n-type zinc oxide thin film and the step of depositing a p-type zinc oxide thin film, indium (In) or aluminum (Al) is included on the n-type zinc oxide thin film Deposition of single or multiple quantum well layers comprising at least one compound selected from gallium nitride (GaN), gallium nitride (GaN) containing no impurities, zinc magnesium oxide (ZnMgO), and zinc cadmium oxide (ZnCdO) Light emitting device manufacturing method characterized in that it further comprises a step. The method of claim 1, wherein the heat treatment is performed at 300 to 1500 ° C. for 1 to 1000 seconds. The thickness of the thin film layer is 1-1,000 nm, The manufacturing method of the light emitting element in any one of Claims 1-5 characterized by the above-mentioned. In the formation of the junction light emitting diode, a step of growing a p-type zinc oxide thin film on the zinc oxide substrate, the step of heat treatment to activate the p-type zinc oxide thin film, and an electrode on the zinc oxide substrate and the p-type zinc oxide thin film Light emitting device manufacturing method comprising the step of forming a. In forming a junction light emitting diode, growing an n-type zinc oxide thin film on the base substrate, sequentially growing a p-type gallium nitride thin film and a p-type zinc oxide thin film on the n-type zinc oxide thin film, the p Activating the zinc oxide thin film by heat treatment, and forming an electrode on the n-type zinc oxide thin film and the p-type zinc oxide thin film. In forming a junction light emitting diode, growing an n-type gallium nitride thin film on the base substrate, sequentially growing a p-type gallium nitride thin film and a p-type zinc oxide thin film on the n-type gallium nitride thin film, the p Activating the zinc oxide thin film by heat treatment, and forming an electrode on the n-type gallium nitride thin film and the p-type zinc oxide thin film. The base substrate of claim 11, wherein the base substrate includes at least one element or compound selected from aluminum oxide (sapphire), silicon (Si), gallium arsenide (GaAs), silicon carbide (SiC), and zinc oxide (ZnO). Light emitting device manufacturing method characterized in that. The light emitting device of claim 11, wherein the dopant material used for depositing the n-type zinc oxide thin film includes at least one element selected from aluminum (Al), gallium (Ga), and indium (In). Way. The dopant material used in depositing a p-type zinc oxide thin film is phosphor (P), rhenium (Re), lithium (Li), sodium (Na) potassium (K), cesium (Cs), antimony (Sb), the light emitting element manufacturing method characterized by including 1 or more types of elements chosen from lead (Pb). 12. The zinc oxide thin film of claim 11, wherein the undoped zinc oxide thin film is deposited on the n-type zinc oxide thin film between the depositing the n-type zinc oxide thin film and the p-type gallium nitride thin film. Light emitting device manufacturing method characterized in that it further comprises a step. The method of claim 11, wherein indium (In) or aluminum (Al) is included on the n-type zinc oxide thin film between the depositing the n-type zinc oxide thin film and the p-type gallium nitride thin film. And depositing a single or multiple quantum well layer comprising at least one compound selected from gallium nitride (GaN) or gallium nitride (GaN) containing no impurities. The method of claim 11, wherein the heat treatment is performed at 300 to 1500 ° C. for 1 to 1000 seconds. The method of manufacturing a light emitting device according to any one of claims 11 to 15, wherein the thickness of the thin film layer is 1 to 1,000 nm. In the formation of the junction light emitting diode, a step of sequentially growing a p-type zinc nitride thin film and a p-type zinc oxide thin film on the zinc oxide substrate, the step of thermally activating the p-type zinc oxide thin film, and the top of the zinc oxide substrate Light-emitting device manufacturing method comprising the step of forming an electrode on the p-type zinc oxide thin film.