KR20000074447A - GaN Semiconductor Light Emitting Device - Google Patents

Abstract

PURPOSE: A nitride semiconductor light emitting device is provided to prevent light emitting efficiency caused by lattice mismatch from being deteriorated and to prevent variation of a light emitting wavelength caused by varied composition of an active layer, by minimizing the lattice mismatch. CONSTITUTION: A nitride semiconductor light emitting device comprises a substrate(200), a buffer layer(210), an n-type contact layer(220), an n-type clad layer(230), an active layer(240), a GaN or AlGaN layer(250), a p-type clad layer(260)/a p-type contact layer(270) and n-type and p-type electrodes(280,290). The buffer layer, n-type contact layer and n-type clad layer are sequentially formed on the substrate. The active layer is formed on the n-type clad layer. The GaN or AlGaN layer is crystallization-grown on the active layer at a low temperature. The p-type clad layer and p-type contact layer are formed on the GaN or AlGaN layer. The n-type and p-type electrodes each is formed in a predetermined portion on the n-type and p-type contact layers.

Description

Nitride Semiconductor Light Emitting Device

The present invention relates to a nitride semiconductor light emitting device, and more particularly, to a nitride semiconductor light emitting device capable of obtaining high efficiency and high output by reducing crystal defects due to lattice mismatch and maximizing light emission efficiency of an active layer.

Nitride semiconductor light emitting 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 LED of 400 nm in the AlGaN LEDs and LDs in the 800 to 830 nm region makes it possible to increase the information recording density by four times or more, thus foretelling the arrival of the digital video disc (DVD) era. In particular, with the development of blue LEDs, the three primary colors of light together with red and green have been achieved, enabling all natural colors to be realized.

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

In the conventional nitride semiconductor light emitting device, as shown in FIG. 1, the substrate 100, the buffer layer 110 and the n-type contact layer 120 sequentially formed on the substrate 100, and the n-type contact layer An n-type clad layer 130 formed on a predetermined portion of the 120, an active layer 140, a p-type cladding layer 160, and a p-type contact sequentially formed on the n-type cladding layer 130. N-type and p formed on the predetermined portion of the layer 170 and the n-type contact layer 120 and the p-type contact layer 170 of the portion where the n-type cladding layer 130 is not formed, respectively. Type electrodes 180 and 190.

Subsequently, although not shown, a nitride semiconductor light emitting device chip which is driven by wire-bonding each of the n-type and p-type electrodes to contact a heat-dissipating heat-sink to flow a current through the electrode portion of the device is provided. To make.

The substrate may be formed of sapphire, GaN, SiC, ZnO, GaAs, or Si, and the buffer layer may be GaN, AlN, AlGaN, or InGaN, but is generally deposited on a sapphire substrate. Vapor Deposition: It is formed by depositing GaN using the MOCVD method).

The n-type and p-type contact layers are GaN by n-type and p-type doping, respectively, and the n-type and p-type cladding layers are AlGaN by n-type and p-type doping, respectively. Is Ti / Al, and Ni / Au is used as the p-type electrode, and the p-type doping for forming the p-type contact layer is formed by doping with Mg.

There are some problems with the conventional conventional nitride semiconductor light emitting device as described above.

First, since the nitride semiconductor light emitting device grows a pn junction nitride semiconductor thin film on a sapphire insulating substrate having a different lattice structure, a lattice mismatch exists between the substrate and the upper crystal growth layer. It is difficult to obtain a high quality crystal growth layer by having a crystal defect (dislocation).

Second, due to the lattice defects of the crystal-grown thin film, n-type is naturally exhibited, and H and Mg of ammonia (NH ₃ ) gas are combined to electrically insulate Mg to form a p-type contact layer. It is difficult to obtain a high concentration of p-type GaN by forming an Mg-H conjugated.

Third, in forming the n-type and p-type electrodes for introducing current into the GaN light emitting device, the driving voltage of the device is consumed because most of the driving voltage is consumed through this because of the band gap offset between the GaN surface and the electrode. There is a problem of getting higher.

The second and third problems have been improved by various studies. However, in order to improve the third problem, a study on p-type activation for minimizing the voltage consumed through the interface between the surface of the GaN and the metal electrode has been conducted. Active progress is being made to lower the voltage, but electrode materials that are not commercially available have yet to be released.

In detail, the first problem of the above problems is that the nitride semiconductor light emitting device has a lattice mismatch between the sapphire substrate and the upper crystal growth layer because crystals grow a pn-junction semiconductor thin film on an insulating sapphire substrate having a completely different lattice structure. (lattice mismatch) is present, it is difficult to obtain a good crystal growth layer due to the crystallization (dislocation) of crystal growth in the crystal grown upper layer and do not do any impurity doping for the production of n-type and p-type GaN Also, since the n-type conductivity is exhibited by surface nitrogen depletion formed during high temperature crystal growth, it is difficult to fabricate a p-type GaN layer having a high carrier concentration.

In addition, the nitride semiconductor light emitting device having a conventional structure has a low melting point of In evaporating in the process of forming a p-type cladding layer which is grown at high temperature on the InGaN active layer, thereby changing the In composition of the active layer. There is a problem that changes.

Accordingly, an object of the present invention is to provide a nitride semiconductor light emitting device capable of minimizing lattice mismatch of a thin film layer formed on an active layer to prevent a decrease in luminous efficiency and to prevent a change in emission wavelength due to a change in In composition.

The nitride semiconductor light emitting device according to the present invention for achieving the above object comprises a substrate, a buffer layer, an n-type contact layer and an n-type cladding layer sequentially formed on the substrate, and an active layer formed on the n-type cladding layer; A low-temperature crystal grown GaN or AlGaN layer on the active layer, a p-type cladding layer and a p-type contact layer formed on the low-temperature crystal grown GaN or AlGaN layer, and the n-type contact layer and the p-type contact layer Each of the n-type and p-type electrodes formed on the predetermined portion.

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

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

<Brief description of symbols for the main parts of the drawings>

200: substrate 210: buffer layer

220: n type contact layer 230: n type clad layer

240: active layer 250: low temperature crystal growth GaN or AlGaN layer

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

280 n-type electrode 290 p-type electrode

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 light emitting device according to an embodiment of the present invention.

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 the n-type contact layer 220 may be provided. N-type cladding layer 230 and active layer 240 sequentially formed in portions, GaN or AlGaN layer 250 formed by low-temperature crystal growth method on the active layer 240, and the low-temperature crystal growth GaN or AlGaN layer The p-type cladding layer 260 and the p-type contact layer 270 sequentially formed on the 250 and the predetermined portion on the n-type contact layer 220 of the portion where the n-type cladding layer 230 is not formed. And n-type and p-type electrodes 280 and 290 formed at predetermined portions on the p-type contact layer 270, respectively.

Subsequently, although not shown, a nitride semiconductor light emitting device chip which is driven by wire-bonding each of the n-type and p-type electrodes to contact a heat-dissipating heat-sink to flow a current through the electrode portion of the device is provided. To make.

The substrate may be formed of sapphire, GaN, SiC, ZnO, GaAs, or Si, and GaN, AlN, AlGaN, or InGaN may be used as the buffer layer, but generally, GaN is deposited on a sapphire substrate by MOCVD. A buffer layer is formed.

The p-type contact layer is p-type GaN by p-type doping, the p-type cladding layer is p-type AlGaN by p-type doping, Ti / Al is the n-type electrode, and the p-type electrode It forms using Ni / Au.

In addition, the growth temperature of the GaN or AlGaN layer by the low temperature crystal growth method of the present invention is 400 ~ 800 ℃, characterized in that lower than the growth temperature of the InGaN active layer.

As described above, in the nitride semiconductor light emitting device of the present invention, a GaN or AlGaN layer is further formed between the active layer and the p-type cladding layer by a low temperature crystal growth method to minimize lattice mismatch of the upper portion of the active layer, and the low temperature process is performed on the active layer. By proceeding to prevent the evaporation of the low melting point caused by the formation of a high temperature layer on the active layer.

Accordingly, the nitride semiconductor light emitting device according to the present invention has the advantage of preventing the reduction of the luminous efficiency due to the lattice mismatch by minimizing the lattice mismatch and the change of the emission wavelength due to the change of the composition of the active layer.

Claims (2)

In a nitride semiconductor light emitting device comprising the formation of a nitride semiconductor multilayer thin film on a substrate, Substrate, A buffer layer, an n-type contact layer and an n-type cladding layer sequentially formed on the substrate; An active layer formed on the n-type cladding layer, A GaN or AlGaN layer grown at low temperature on the active layer; A p-type cladding layer and a p-type contact layer formed on the low temperature crystal grown GaN or AlGaN layer; And n-type and p-type electrodes respectively formed in predetermined portions on the n-type contact layer and the p-type contact layer. The nitride semiconductor light emitting device of claim 1, wherein the low-temperature crystal-grown GaN or AlGaN layer is formed at a temperature in the range of 400 to 800 ° C. lower than the crystal growth temperature of the active layer.