KR20010008571A - Gan semiconductor white light emitting device - Google Patents

Abstract

PURPOSE: A GaN semiconductor white light emitting device is provided to enhance luminescent efficiency in the form of direct light-emission from the inside of a light emitting device chip by adopting luminescent regions of the three primary colors in an active layer. CONSTITUTION: A GaN semiconductor white light emitting device includes a buffer layer(210) and an n-type contact layer(220) formed on a substrate(200) in sequence. The device further includes an n-type clad layer(230) formed on a portion of the n-type contact layer(220), the n-type clad layer(230) having three V-shaped grooves(a,b,c) formed thereon with different depth and width. On the n-type clad layer(230), an active layer(240) of InGaN, a low temperature crystal growth layer(250), a p-type clad layer(260) and a p-type contact layer(270) are formed in sequence. In addition, an n-type electrode(280) is formed on the other portion of the n-type contact layer(220), and a p-type electrode(290) is formed on the p-type contact layer(270). Particularly, the InGaN active layer(240) has the composition of indium formed differently in the respective grooves(a,b,c).

Description

Nitride Semiconductor White Light Emitting Device

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nitride semiconductor white light emitting device. In particular, a nitride semiconductor white light emitting device capable of increasing luminous efficiency by introducing red, green, and blue three-color light emitting regions into an active layer to emit light directly from inside a light emitting device chip. It is about.

Nitride semiconductor devices have recently attracted much attention as materials such as blue light emitting diodes (hereinafter referred to as LEDs), blue laser diodes (hereinafter referred to as LDs), or solar cells.

Among them, the short wavelength blue LEDs in the 400 nm range for the AlGaAs LEDs and LDs in the 800 to 830 nm region enable the information recording density to be increased by four times or more, thus foretelling the arrival of the digital video disc (DVD) era.

In particular, the development of a blue LED achieves the three primary colors of light together with red and green to facilitate the implementation of all natural colors.

1 is a cross-sectional view schematically showing a nitride semiconductor white light emitting device according to the prior art.

As shown in FIG. 1, a device 110 formed by stacking a multilayer nitride semiconductor thin film on an insulating substrate 100 such as sapphire or SiC, and a lower surface of the substrate 100 on which the device 110 is not formed. In order to prevent light from entering the synthetic resin for die bonding, coating metal such as In, Cu, Pd, Rh, W, Mo, Ti, Ni, Al and Ag or conductive materials such as TiO ₂ , SiO ₂ and BaF ₂ And a die-bonding synthetic resin layer 130 formed using an epoxy resin, a silicon resin, or the like containing Au, Ag, Al, and Cu in order to increase thermal conductivity between the chip and the lead frame. And wires 120 and 125 for connecting the device to the lead frames 135 and 145, and a silicone resin and an amorphous fluorine resin in a gel form. or light-transmitting polyimide (polymide) a color conversion material with a resin and a Y ₃ Al ₅ O type consisting of _two Material layer 150 is formed so as to cover the element 110.

By using the fluorescent material Y ₃ Al ₅ O ₂ in the blue light emitting device having a wavelength of 450 nm as excitation light it is possible to obtain light in the visible light region of 530 ~ 580 nm. It is also possible to replace Al with Ga to shorten the light emission wavelength and to replace Y with Gd to make the long wavelength.

As described above, the white light emitting device manufactured by using the conventional blue light as the excitation light source has a low luminous efficiency and uses a secondary transition material, so that the overall size of the device is large, which limits the miniaturization of the packaged white light emitting device. There is also a growing problem. In addition, high power and ultra-short wavelength light source of 300 nm or less are required for the development of the conventional white light emitting device, but the development of the ultra-short wavelength light emitting device is a research and development stage, which requires a little time to be put into practical use.

Accordingly, an object of the present invention is to directly emit light by controlling the In composition of the InGaN active layer, which is a ternary nitride semiconductor, instead of a transition method using a fluorescent material in a conventional blue light emitting device, thereby increasing luminous efficiency, and a low-cost, high-output nitride semiconductor white light emitting device. In providing.

The nitride semiconductor white light emitting device according to the present invention for achieving the above object is formed by sequentially stacking an n-type contact layer, n-type cladding layer, InGaN active layer, low-temperature crystal growth layer, p-type cladding layer and a contact layer on the substrate In the nitride semiconductor device to be formed, the In composition of the InGaN active layer formed in each groove is formed differently by forming the V-shaped first to third grooves having different depths and widths in the upper layer of the n-type cladding layer. It features.

1 is a cross-sectional view schematically showing a nitride semiconductor white light emitting device according to the prior art.

2 is a cross-sectional view showing a nitride semiconductor white light emitting device according to an embodiment of the present invention.

3 is a partial cross-sectional view showing InGaN deposited on an n-type cladding layer.

<Detailed description of the reference numerals of the main parts of the drawings>

200: substrate 210: buffer layer

220: n-type contact layer 230: n-type cladding layer having a V-shaped groove

240: active layer 250: low temperature crystal growth layer

260 p-type cladding layer 270 p-type contact layer

a: first groove b:: second groove

c: third groove

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

FIG. 2 is a cross-sectional view illustrating a nitride semiconductor white light emitting device according to an exemplary embodiment of the present invention, and FIG. 3 is a cross-sectional view illustrating InGaN grown on an n-type cladding layer having V-shaped first to third grooves.

InGaN, a ternary compound semiconductor, is a direct transition solid solution formed by mixing InN having an energy band gap of 1.9 eV and GaN having 3.4 eV. Therefore, the energy band gap can vary from 1.9 eV to 3.4 eV by the composition of In.

However, since InN and GaN have a very large lattice constant difference of about 11%, there is a range of miscibility gaps in mixing GaN and InN. InGaN solid solution in this mixed gap region is thermodynamically unstable, causing spontaneous decomposition into two thermodynamically stable phases. This phase separation results in spatially disordered distribution of a high In content phase in a matrix having a low In content.

The composition of the two phases separated from the GaN-In state gradient at the growth temperature of 760 ° C is approximately 22% and 80%. The phases of the composition may emit light in purple and red regions, respectively, when viewed at energy intervals.

Another composition predicted from the state diagram is about 44% of indium (In) content, which corresponds to the intermediate phase in thermodynamic quasi-stable state, and may emit light in the green region.

Therefore, by controlling the growth conditions during InGaN growth, the In composition ratio of the separated phases can be adjusted to fabricate a white light emitting device based on the color sum of the basic three primary colors of blue, green, and red.

In the present invention, a nitride semiconductor white light emitting device fabricated using the above In phase separation phenomenon is illustrated in FIG. 2.

As shown in FIG. 2, the substrate 200, the buffer layer 210 and the n-type contact layer 220 sequentially formed on the substrate 200, and a predetermined portion on the n-type contact layer 220 are disposed on the substrate 200. And an n-type clad layer 230 having V-shaped first to third grooves (a) (b) (c) having different depths and widths formed thereon, and the first to third grooves ( a) (b) (c) formed sequentially on the n-type cladding layer 230, the active layer 240, low temperature crystal growth layer 250, p-type cladding layer 260 and p-type contact layer 270 It has a double hetero structure consisting of a predetermined portion on the n-type contact layer 220, the n-type cladding layer 230 is not formed and a predetermined portion on the p-type contact layer 270, respectively and n-type and p-type electrodes 280 and 290.

Although not shown, a nitride semiconductor white light emitting device chip is driven by wire-bonding each n-type and p-type electrode to contact a heat-dissipating heat-sink to apply a current to the electrode portion. do.

The n-type cladding layer is formed by sequentially stacking a buffer layer, an n-type contact layer, and an n-type cladding layer on a substrate, and performing dry etching or a scriber on the formed n-type cladding layer. In the upper portion of the n-type cladding layer, a plurality of V-shaped first to third grooves having different depths and widths were formed.

In the nitride semiconductor white light emitting device having the above-described structure, sapphire, GaN, SiC, ZnO, GaAs, or Si is used as the substrate, and GaN, AlN, AlGaN, or InGaN is used as the buffer layer. The buffer layer formed by depositing GaN using a method of metal organic chemical vapor deposition (Metal Organic Chemical Vapor Deposition) is used.

In addition, the active layer is formed of InGaN causing a phase separation phenomenon, the low temperature crystal growth layer formed between the active layer and the p-type cladding layer is formed of GaN to buffer the lattice mismatch between the active layer and the p-type cladding layer. .

The low temperature crystal growth layer is to control the precise In composition in the active layer formed on the n-type cladding layer having the plurality of V-shaped grooves, and forms a p-type cladding layer which is a high temperature crystal growth process of 1000 ° C. or more on the active layer. When the low melting point In in the active layer evaporates, it becomes difficult to control the In composition. In addition, when the low temperature crystal growth layer is formed, the low temperature crystal growth layer may minimize lattice mismatch of the p-type crystal growth layer formed on the active layer to prevent a decrease in luminous efficiency caused by lattice mismatch.

FIG. 3 is a cross-sectional view illustrating a crystal growth process of InGaN for forming an active layer on an n-type cladding layer having V-shaped first to third grooves.

As shown in FIG. 3, the first to third InGaN 240a formed in the respective grooves on the n-type cladding layer 230 having the V-shaped first to third grooves (a) (b) (c) having different depths and widths. 240b and 240c, which are formed on the cladding layer 230 having the first to third grooves (a), (b) and (c) having different depths and widths. In compositions of InGaN 240a, 240b, and 240c are formed differently.

That is, the crystal growth rate of the InGaN active layer formed on the V-shaped first to third grooves (a) (b) (c) having different depths and widths is the lowest in the third grooves (c) having the deepest valleys. Since it is faster than the first groove (a), the composition of In is different according to the shape of the groove, and the time when the third groove (c) having a deep valley of the V-shaped groove is the same as the first groove (a) having a low valley, Since the composition has a relatively high In composition at the same temperature, red, green, and blue light emission from each of the first to third grooves (a), (b), and (c) are induced, and the single color combination effect of the three primary colors A white light emitting device in which white light is emitted therein is formed.

Accordingly, the nitride semiconductor white light emitting device according to the present invention is a type of directly emitting light by introducing a three primary color light emitting region into the active layer, and thus does not use a conventional phosphor or other secondary transition material, and thus has a high luminous efficiency and a simple device manufacturing process. It is possible to manufacture a white light emitting device having a high output, high-quality single chip form of size.

Claims (1)

In a nitride semiconductor device formed by sequentially stacking an n-type contact layer, an n-type cladding layer, an InGaN active layer, a low temperature crystal growth layer, a p-type cladding layer and a contact layer on a substrate, A nitride semiconductor white light emitting device, characterized in that V-shaped first to third grooves having different depths and widths are formed in an upper portion of the n-type cladding layer so that In compositions of the InGaN active layers formed in the respective grooves are different from each other. device.