KR20010068015A - METHOD FOR PRODUCING SHORT WAVELENGTH ZnO LED ACCORDING TO THE TEMPERATURE OF DEPOSITION - Google Patents

Abstract

PURPOSE: A method for manufacturing a ZnO light emitting device with a short wavelength according to a deposition temperature is provided to improve a light emitting characteristic by controlling a deposition temperature when forming a p-type material. CONSTITUTION: A sapphire substrate is formed by using a p-type material. A ZnO layer of an n-type material is deposited on an upper portion the sapphire substrate under a predetermined temperature. A lower electrode and an upper electrode are formed on upper portions of the sapphire layer and the ZnO layer. In the process for depositing the ZnO on the sapphire substrate, the temperature for depositing the ZnO is 650 to 750 degrees centigrade.

Description

METHODS FOR PRODUCING SHORT WAVELENGTH ZnO LED ACCORDING TO THE TEMPERATURE OF DEPOSITION}

The present invention relates to a method for manufacturing a short-wavelength ZnO light emitting device according to the deposition temperature, and more specifically, to apply ZnO as an n-type and to form a p-type material to be bonded to the ZnO to generate short wavelengths. The present invention relates to a method for manufacturing a short wavelength ZnO light emitting device according to a deposition temperature which improves light emission characteristics by controlling temperature.

As is well known, displays in electronic devices and devices have an important function of acting as an interface between people by visualizing abstract information. Many applications have been realized in conventional displays, each with its own specific requirements. Accordingly, various display technologies have been developed, each of which has its own strengths and weaknesses in terms of the requirements of a particular display application, and a particular display technology is best suited for a particular kind of application.

BACKGROUND OF THE INVENTION Light emitting diodes (LEDs) which spontaneously emit light under forward bias conditions have various applications, such as indicators, visual display devices, light sources for optical data links, optical fiber communications, and the like.

In most applications, for light generation, direct electronic band-to-band transitions or impurity-induced indirect band transitions in the material forming the active region of the LED. -to-band transitions are used. In these cases, the energy gap of the material selected for the active area of the LED, ie the zone in which the electronic transition, which serves to generate light within the LED, determines the color of the particular LED. do.

Another known concept to exploit the energy of the dominant optical transition of a particular material and the wavelength of light generated therein is to include impurities that cause a deep trap in the energy gap. In this case, daylight transition can occur between the band-state of the host material and the energy level of the deep trap.

Therefore, an appropriate selection of impurities can cause optical radiation having photon energy below the energy gap of the host semiconductor.

Today, using these two concepts of adjusting the emission wavelength of an LED and using a III-V or II-VI compound semiconductor or an alloy thereof for the active area of the LED, discrete emission lines It can cover the optical spectrum between near infrared and blue with.

Blue light emitting MIS diodes have been realized in the GaN series. Examples of these have been published below:

H. blood. "Violet luminescence of Mg-doped GaN" Applied Physics Letters, Vol. 22, no. 6, pp. 303-305, 1973.

-Jay. I. Pankove, "Blue-Green Numeric Display Using Electroluminescent GaN" RCA Review, Vol. 34, pp. 336-343, 1973.

-M. egg. H. M. R. H. Khan et al. "Electric properties of GaN: Zn MIS-type light emitting diodes" Physica B 185, pp. 480-484, 1993.

-G. "GaN electroluminescent devices: preparation and studies" by G. Jacob et al. Journal of Luminescence Vol. 17, pp. 263-282, 1978.

EP-0-579 897 A1: "Light-emitting device of gallium nitride compoundsemiconductor".

Unfortunately, current LEDs have several drawbacks. Light emission in LEDs is spontaneous and is limited in size to about 1 to 10 nanoseconds in time. Therefore, the modulation rate of the LED is also limited by the natural life of the LED.

Thus, there have been several attempts to improve the performance of LEDs. One of them is the development of a short wavelength blue semiconductor light emitting device. As a characteristic material for realizing this, gallium nitride compound semiconductors, such as GaN, InGaN, GaAlN, InGaAlN, etc., are currently considered.

For example, room temperature pulse oscillations with wavelengths of 380 to 417 have been confirmed in semiconductor light emitting devices using GaN-based materials.

However, sufficient characteristics cannot be obtained in a semiconductor laser using a GaN-based material, and the variation of the threshold voltage and the value for the room temperature pulse oscillation region of 10 to 40 V becomes large.

This change is due to the difficulty of crystal growth and large device resistance of the gallium nitride compound semiconductor. In particular, it is not possible to form a p-type gallium nitride compound layer having a smooth surface and a high carrier density. Furthermore, the high contact resistance of the p-side electrode causes a large voltage drop, which causes the semiconductor layer to deteriorate due to heat generation and metal reaction even when pulse oscillation is operated. Taking into account the cheating value, room temperature continuous oscillation cannot be achieved until the threshold voltage is reduced below 10V.

Moreover, when a current required for laser generation is applied, a high current flows locally and the carrier cannot be evenly injected into the active layer, resulting in a momentary breakdown of the device. As a result, continuous light emission becomes difficult.

The GaN-based light emitting device has a high p-side electrode contact resistance, which increases the operating voltage. Furthermore, nickel, which functions as the p-side electrode metal, and gallium, which forms the p-type semiconductor layer, react with each other to melt, resulting in lower electrical conductivity. As a result, it is very difficult to continuously emit light.

In addition, SiC and ZnO are known as light emitting materials having short wavelengths.

However, the SiC and ZnO described above also have disadvantages in that the chemical single crystal is very unstable or difficult to crystallize in order to be used as a compound semiconductor required for blue light emission. In the case of SiC, it is chemically stable, but there is a problem in that it is low in life and brightness for practical use.

On the other hand, in the case of ZnO, in the structure of the band gap and the crystal, it has similar characteristics to GaN, which is not only suitable as a material for blue light emission or shorter wavelength light emission, but also about 3 times (for example, 60 meV) GaN. Since it has excitation binding energy, it is considered to be a very suitable material as a material material for the next generation of short wavelength optical devices.

Nevertheless, although the ZnO is manufactured by p-n junction, there is a problem that the luminous efficiency is very low, so it is very unlikely to be used as an actual device, and that ZnO is very difficult to form a p-type material.

In addition, even when an appropriate short wavelength optical element material is selected, a difference in the manufacturing process greatly affects the short wavelength optical element, and therefore, a suitable manufacturing method must be selected in order to improve light emission characteristics. However, at present, research on short wavelength optical devices is very incomplete, and there is almost no research on a manufacturing method for improving the light emitting characteristics of the optical devices.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described prior art, by forming a sapphire substrate (Al ₂ O ₃ ) in a p-type and controlling the deposition temperature when depositing a ZnO thin film on the upper surface of the sapphire substrate. It is an object of the present invention to provide a method for manufacturing a short-wavelength ZnO light emitting device according to deposition temperature, which achieves stable crystal bonding and improves light emission characteristics thereof.

1 is a cross-sectional view illustrating a process of forming a p-n junction layer in a method of manufacturing a short wavelength ZnO light emitting device according to an embodiment of the present invention;

2A, 2B, 2C, and 2D illustrate changes in visible light emission characteristics according to deposition temperatures of short wavelength ZnO light emitting devices according to an exemplary embodiment of the present invention.

* Description of the symbols for the main parts of the drawings *

2: Al ₂ O ₃ substrate, 4: ZnO layer,

6: lower electrode, 8: upper electrode.

In order to achieve the above object, according to a preferred embodiment of the present invention, in the method of manufacturing a pn junction light emitting diode using ZnO as a main material, forming a sapphire substrate (Al ₂ O ₃ ) of the p-type material and ; Depositing a ZnO layer, which is an n-type material, on a sapphire substrate (Al ₂ O ₃ ) at a specific temperature; Provided is a method of manufacturing a short wavelength ZnO light emitting device according to deposition temperature, comprising forming a lower electrode and an upper electrode on an upper surface of the sapphire substrate (Al ₂ O ₃ ) and the ZnO layer.

Preferably, the temperature for depositing ZnO on the upper surface of the sapphire substrate (Al ₂ O ₃ ) is provided a method for manufacturing a short wavelength ZnO light emitting device according to the deposition temperature, characterized in that the deposition temperature.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail with reference to drawings.

1 is a cross-sectional view illustrating a process of forming a p-n junction layer in a method of manufacturing a short wavelength ZnO light emitting device according to an embodiment of the present invention.

Referring to this, the ZnO element 4 is deposited on the upper surface of the sapphire substrate (Al ₂ O _3: 2) to be used as the p-type to be used as the n-type region.

At this time, the short wavelength ZnO light emitting device is a p-n junction short wavelength light emitting device using ZnO, which is a group II-VI semiconductor having a wide band gap of 3.37 eV and having direct transition characteristics as a form of hexagonal WURTZITE coupling structure.

The n-type ZnO layer 4 is applied to the upper surface of the p-type substrate (eg, sapphire substrate: 2) formed in the above process and deposited in a mesa structure. As a result, a pn junction layer is formed, whereby visible light is only generated by the p-type substrate (sapphire substrate: 2) and the n-type layer (ZnO: 4) layer. It does not emit light by bonding the substrate: 2) and the n-type layer (ZnO: 4).

Accordingly, in the present invention, when the p-type substrate (sapphire substrate: 2) and the n-type layer (ZnO: 4) are bonded to each other, the light emission characteristics due to the control of the deposition temperature are considered to emit visible light of a desired color. To make a device.

Hereinafter, a manufacturing method according to the deposition temperature of the short wavelength ZnO light emitting device will be described in detail with reference to the accompanying drawings.

2A, 2B, 2C, and 2D illustrate changes in visible light emission characteristics according to deposition temperatures of short wavelength ZnO light emitting devices according to an exemplary embodiment of the present invention.

Referring to this, the present invention is a manufacturing process to check the visible light emission characteristics according to the change value at the deposition temperature of the short wavelength ZnO light emitting device, and to improve the light emission characteristics of the short wavelength ZnO light emitting device.

That is, the present invention is a method for manufacturing a short-wavelength ZnO light emitting device by controlling the wavelength region by changing the deposition temperature during the formation of the light emitting thin film as a preliminary step for forming a pn junction light emitting device in the visible light region using ZnO. Contains various natural defects.

For example, -0.05 eV or -0.2 eV is reported at the induction band edge in the case of invasive Zn, and -0.05 eV or -0.2 eV in the case of O-vacancy. According to Gopel and Egelhaaf et al, they act as donors in the O vacancy and are located at -0.04 eV or -0.19 eV at the conduction band edge, and -2.5 eV in the Zn vacancy.

In the present invention, it is possible to control the visible light emission characteristics without the doping process by adjusting the deposition temperature for the above-mentioned natural defects.

Accordingly, in the present invention, when the deposition conditions of 400 ℃ and 500 ℃ are applied as a result of considering the emission characteristics by applying the deposition temperature within the range of 300 ℃ to 1000 ℃ in the same configuration and other conditions in the present invention 2A and FIG. As shown in 2b, the light density graph with respect to the wavelength is not linear at about 400 nm or less, and almost no light emission is performed at more than that.

Figure 2c is a graph of the light emission characteristics while changing the deposition temperature of the thin film from 550 ℃ to 650 ℃, the blue and yellow light emission with a very high light density is achieved.

On the other hand, when the deposition temperature of the thin film was changed from 650 ° C. to 750 ° C., blue and yellow light emission occurred similarly to the deposition temperature of 550 ° C. to 650 ° C., but the light density was slightly decreased. .

Therefore, the manufacturing of the short wavelength ZnO light emitting device according to the present invention exhibits excellent blue light emission characteristics, which is desirable to maintain the deposition temperature of the thin film at 550 ° C to 650 ° C. This is because when the ZnO device having a natural defect is deposited at a deposition temperature of 650 ° C to 750 ° C, the defect level is formed inside the band gap.

In addition, a ZnO layer 4 is deposited on the top surface of the sapphire substrate (Al ₂ O ₃ ) at a deposition temperature of 650 ° C. to 750 ° C., and then a lower electrode 6 is formed on the sapphire substrate (Al ₂ O ₃ ). When the upper electrode 8 is formed on the ZnO 4 and the forward bias voltage is applied, the desired blue light is emitted with excellent light emission characteristics.

On the other hand, the manufacturing method of the short-wavelength ZnO light emitting device according to the deposition temperature according to the embodiment of the present invention is not limited only to the above embodiment, but various modifications can be made without departing from the technical gist of the present invention.

As described above, the manufacturing method of the short wavelength ZnO light emitting device according to the deposition temperature according to the present invention has a similar characteristic as GaN and is a material material in the next generation short wavelength optical device for emitting blue light or shorter wavelength. In the previous step for fabricating ZnO-based LEDs, which are considered suitable materials, the short-wavelength ZnO light emitting devices manufactured by maintaining a specific deposition temperature (650 ° C. to 750 ° C.) during the fabrication of ZnO-based short wavelength semiconductor light emitting devices may emit light. There is an effect that the characteristic becomes better and the blue light density becomes higher.

Claims (2)

In the manufacturing method of p-n junction light emitting diode using ZnO as a main material, forming a sapphire substrate (Al ₂ O ₃ ) from a p-type material; Depositing a ZnO layer, which is an n-type material, on a sapphire substrate (Al ₂ O ₃ ) at a specific temperature; A method of manufacturing a short wavelength ZnO light emitting device according to deposition temperature, comprising forming a lower electrode and an upper electrode on an upper surface of the sapphire substrate (Al ₂ O ₃ ) and the ZnO layer. 2. The method of claim 1, wherein the temperature of depositing ZnO on the top surface of the sapphire substrate (Al ₂ O ₃ ) is 650 ° C. to 750 ° C. 6.