KR20010009602A - Gan semiconductor white light emitting device - Google Patents

Abstract

PURPOSE: GaN semiconductor white light emitting device is provided to increase a light emitting efficiency by controlling In composition of InGaN active layer instead of a transition method using a fluorescent material. CONSTITUTION: GaN semiconductor white light emitting device includes an insulation substrate(200), N-type contact layer(220), N-type clad layer(230), a current limit layer(240), InGaN active layer, a low-temperature crystal growing layer(260), P-type clad layer(270), and a contact layer. The N-type contact layer and the N-type clad layer are sequentially formed on the insulation substrate. The current limit layer having a different depth and different width form many V-shape grooves on the N-type clad layer. The InGaN active layer, the low-temperature crystal growing layer(260), the P-type clad layer(270), and the contact layer are sequentially formed on the current limit layer having V-shaped grooves. Thereby, the GaN semiconductor white light emitting device increases a light emitting efficiency by controlling In composition of InGaN active layer instead of a transition method using a fluorescent material.

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 has a depth and width on the insulating substrate, the n-type contact layer, the n-type cladding layer and the n-type cladding layer sequentially formed on the insulating substrate And a current limiting layer in which a plurality of V-shaped grooves are formed, and an InGaN active layer, a low temperature crystal growth layer, a p-type cladding layer, and a contact layer sequentially formed on the current limiting layer in which the plurality of V-shaped grooves are formed.

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.

3A to 3C are cross-sectional process diagrams illustrating a process of forming an active layer on an n-type cladding layer in a method of manufacturing a nitride semiconductor white light emitting device according to the present invention;

<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 clad layer

240: current limiting layer with a V-shaped groove

250: active layer 260: low temperature crystal growth layer

270 p-type cladding layer 280 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.

2 is a cross-sectional view illustrating a nitride semiconductor white light emitting device according to an exemplary embodiment of the present invention, and FIGS. 3A to 3C illustrate an active layer formed on an n-type clad layer in a method of manufacturing a nitride semiconductor white light emitting device according to the present invention. It is a cross-sectional process chart which shows a process.

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.

2, a substrate 200, a buffer layer 210, an n-type contact layer 220 and an n-type clad layer 230 sequentially formed on the substrate 200, A current limiting layer 240 having first to third grooves (a) (b) (c) having different depths and widths on the n-type cladding layer, and sequentially on the current limiting layer 240 The active layer 250, the low temperature crystal growth layer 260, the p-type cladding layer 270, and the p-type contact layer 280 have a double hetero structure, and the n-type cladding layer 230 is formed. And n-type and p-type electrodes 290 and 295 formed at predetermined portions on the non-formed n-type contact layer 220 and predetermined portions on the p-type contact layer 280, respectively.

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 current limiting layer is formed by depositing GaAs on the n-type cladding layer and wet etching the GaAs to form a V-shaped mesa having a width of 5 to 10 μm.

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 for controlling the precise In composition in the active layer formed on the current limiting layer. When the p-type cladding layer, which is a high temperature crystal growth process of 1000 ° C. or more, is formed on the active layer, the low melting point In in the active layer evaporates. In composition becomes difficult to control. 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.

3A to 3C are cross-sectional process views illustrating a process of forming an active layer on an n-type cladding layer in the method of manufacturing a nitride semiconductor white light emitting device according to the present invention.

After growing GaAs on GaN or growing GaN on GaAs as shown in FIG. 3A, the back surface of the GaAs is polished and smoothly processed, and then photoresist is formed on the upper GaN or GaAs layer 320 described above. ), And a plurality of photoresist patterns 330 are formed on the GaN or GaAs layer 320 to expose surfaces of different widths W1, W2, and W3.

As shown in FIG. 3B, the GaAs layer 320 is opened by using the photoresist pattern 330 as an etching mask and using an etching solution such as H ₂ SO ₄ or NH ₄ OH, which is a general GaAs etching solution. After the wet portion is wet etched, the photoresist pattern 330 is removed to form a mesa current limiting layer 340 having V-shaped first to third grooves a, b, and c.

As shown in FIG. 3C, InGaN is deposited on the current limiting layer 340 to form an active layer 350. At this time, the In composition of InGaN deposited on the V groove of the current limiting layer 340 having different widths is formed differently. That is, the crystal growth rate of the InGaN active layer 350 formed on the V-shaped first to third grooves (a) (b) (c) having different depths and widths is the highest in the third grooves c having the deepest valleys. Since the valley is faster than the lower first groove (a), the composition of In is different according to the shape of the groove, and the third groove (c) having a deep valley of the V-shaped groove is smaller than the lower groove (a). At the same time and at the same temperature, the composition has a relatively high In composition, thereby inducing red, green, and blue light emission from each of the first to third grooves (a), (b), and (c). As a result, a white light emitting device is formed in which white light is emitted within a single chip.

That is, the nitride semiconductor white light emitting device according to the present invention introduces a V-shaped current limiting layer by depositing and patterning GaAs, which is easily wet-etched, between the n-type cladding layer and the active layer, thereby operating current flowing through the device when driving the device. By limiting the flow to the inside of the V-shaped with a limited width, not only the current limit in the transverse direction perpendicular to the crystal growth direction was induced, but also the current limitation in the longitudinal direction, which is the crystal growth direction due to the thickness limitation of the InGsN active layer, was simultaneously induced.

Accordingly, in the nitride semiconductor white light emitting device according to the present invention, by introducing a V-shaped current limiting layer between the n-type cladding layer and the active layer, it is possible to lower the threshold current value required for driving the device and to form a V-shaped groove. The wet etching method has the advantage of simplifying the device manufacturing process and improving reproducibility. In addition, the light emission efficiency is high by adopting three primary color light emitting regions inside the active layer and does not use existing phosphors or other secondary transition materials, and it is possible to manufacture small size, high output, high quality single chip type white light emitting devices. There is an advantage.

Claims (2)

With insulation board, An n-type contact layer and an n-type cladding layer sequentially formed on the insulating substrate; A current limiting layer in which a plurality of V-shaped grooves having different depths and widths are formed on the n-type cladding layer; A nitride semiconductor white light emitting device comprising an InGaN active layer, a low temperature crystal growth layer, a p-type cladding layer, and a contact layer sequentially formed on a current limiting layer having a plurality of V-shaped grooves. The method of manufacturing a nitride semiconductor white light emitting device according to claim 1, wherein the V-shaped groove spacing of the current limiting layer is 5 to 10 µm.