KR20010076808A - III-Nitride Semiconductor device - Google Patents

Abstract

PURPOSE: A nitrite semiconductor device is provided to improve the crystal characteristic of a nitrite semiconductor film formed on a buffer layer by improving the characteristic of the buffer layer. CONSTITUTION: The nitrite semiconductor device includes a buffer layer(110). The nitrite semiconductor film is formed on a hetero-substrate. The buffer layer has a chemical expression of InxAl(1-x)N(0<x=<1). Furthermore, the InxAl(1-x)N(0<x=<1) buffer layer further includes an InxAl(1-x)N grown with a component ratio same to that of x while x satisfies (0<x=<1) or InxAl(1-x)N whose combination is slanted linearly or non-linearly. The buffer layer is formed at a temperature in the range of 300 to 900 degrees. Alternatively, InxAlyGa(1-x-y)N(0 smaller than or equal to (x+y) smaller than 1) buffer layer is further included between the InxAl(1-x) buffer layer and the nitrite semiconductor film.

Description

Nitride semiconductor device {III-Nitride Semiconductor device}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nitride semiconductor device, and more particularly to a nitride semiconductor device having a low driving voltage and high luminous efficiency in a nitride semiconductor light emitting device by increasing the crystallinity of a nitride semiconductor formed on a heterogeneous substrate by using an InAlN buffer layer. It is about.

Nitride semiconductors GaN, AlN, and InN have a wide band gap ranging from 1.9 to 6.2 eV, and thus, bandgap engineering using them is very much in terms of obtaining three primary colors of light through semiconductors. Research and investment are being made.

In fact, the development of blue and green light emitting devices using nitride semiconductors has revolutionized the optical display market and is considered as one of the most promising industries that can create high added value in the future. However, in order to achieve the smooth industrialization of such nitride-based light emitting devices, it is essential to lower the driving voltage of the device and to increase the light emission luminance.

In addition, until the same type of substrate for growing a nitride semiconductor has not been developed until now, there is a problem that a heterogeneous material such as sapphire, Si, GaAs, SiC, or ZnO should be used as the substrate. Therefore, in order to grow a thin film having good characteristics on the substrate materials, a buffer layer composed of a nitride semiconductor series is formed in a temperature range of 400 ° C to 900 ° C.

The formation of the buffer layer mitigates the deformation force caused by the difference in lattice constant and thermal expansion coefficient between the substrate and the nitride semiconductor thin film, and serves as a nucleus for forming the nitride semiconductor thin film to provide an appropriate surface structure. Known. In the case where the nitride semiconductor thin film is formed without actually forming the buffer layer, the surface of the nitride semiconductor thin film is formed in a pattern having a hexagonal structure, whereas the thin film grown after the buffer layer is formed in a pattern having a smooth surface structure. do.

Therefore, in order to form a high quality nitride semiconductor thin film on a substrate having a difference in lattice constant and thermal expansion coefficient in a high efficiency nitride semiconductor light emitting device, it is necessary to form a buffer layer that can provide optimum conditions.

Buffer layers used in nitride light emitting devices that are commercially available to date include GaN (Jpn. J. Appl. Phys. 30, L1750 (1991)), AlN (Appl. Phys. Lett. 48, 353 (1986) grown at low temperatures. ), AlGaN (J. Appl. Phys. 28, 2378 (1997)) or InGaN (2nd International Symposium Proceeding on "Blue Laser and LED", 433 (1998)) and the like.

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

As shown in FIG. 1, a heterogeneous material such as sapphire, Si, GaAs, SiC, or ZnO is used as a substrate 10 to form a nitride semiconductor device, and thus, a high quality nitride semiconductor thin film 30 is formed on the substrate 10. GaN, AlN, AlGaN, or InGaN is deposited and used as the buffer layer 20 to form a. As described above, the buffer layer 20 serves to alleviate the lattice mismatch difference and thermal expansion coefficient difference between the heterogeneous material substrate 10 and the nitride semiconductor thin film 30 to be formed on the substrate 10.

As described above, the conventional nitride semiconductor light emitting device using a buffer layer such as GaN, AlN, AlGaN or InGaN still has a dynamic resistance of 25Ω, an external quantum efficiency of 5%, and an operating voltage of 3.5V at a driving current of 20 mA. It shows a high value and it is considered very difficult to lower the driving voltage even at 0.1V above.

Therefore, it is very important to improve the performance of the light emitting device by improving the crystallinity of the nitride semiconductor thin film by improving the characteristics of the buffer layer.

Accordingly, an object of the present invention is to provide a nitride semiconductor device capable of improving the crystallinity of a nitride semiconductor thin film formed on the buffer layer by improving the characteristics of the buffer layer.

In the nitride semiconductor device according to the present invention for achieving the above object, in forming a nitride semiconductor thin film on a dissimilar substrate, to further form an In _x Al _1-x N (0 <x ≤ 1) buffer layer on the substrate It is characterized by.

1 is a partial sectional view schematically showing a nitride semiconductor element according to the prior art.

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

3 is a graph showing x-ray diffraction curves of undoped GaN thin films formed on different buffer layers.

4 is a graph showing the half widths of the x-ray diffraction curves of undoped GaN thin films formed on different buffer layers.

<Explanation of symbols for the main parts of the drawings>

100 substrate 110 first buffer layer

120: second buffer layer 130: nitride semiconductor thin film

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

2 is a partial cross-sectional view of a nitride semiconductor device according to an embodiment of the present invention, Figure 3 is a comparative graph showing the x-ray diffraction curve when a nitride semiconductor thin film is formed using a conventional buffer layer and the buffer layer of the present invention. 4 is a graph comparing half-width values of the x-ray diffraction curve of FIG. 3.

In the present invention, as shown in FIG. 2, the In _x Al _1-x N first buffer layer 110 is generally deposited on a heterogeneous substrate 100 for forming a nitride semiconductor device at a temperature of 300 to 900 ° C. (Metal Organic Chemical Vapor Deposition: hereafter referred to as MOCVD) to form a thickness of 20 ~ 1000 mm by using a method. Wherein the first buffer layer 110 is a composition ratio of In 0 <x ≤ If the composition in the growth of the same composition ratio of In _x Al _1-x N and a linear or non-linear picture in the range of 1, In _x Al _{1 -x} Include N. The composition of In may be controlled by controlling the flow rates of trimethylindium and trimethylaluminum during growth of In _x Al _1-x N.

Subsequently, In _x Al _y Ga _1-xy N (0) to prevent dissociation of In of the first buffer layer 110 when the temperature increases to form a nitride semiconductor thin film on the first buffer layer 110. ≦ x + y ≦ 1) is deposited using a MOCVD method to a thickness in the range of 5 to 1000 GPa to form the second buffer layer 120.

Subsequently, the nitride semiconductor thin film 130 is formed on the second buffer layer 120 at a high temperature of 1000 ° C. or more. At this time, regardless of the buffer layer according to the present invention or the prior art, since all the nitride semiconductor thin films 130 have almost the same electron concentration as about 1 × 10 ¹⁷ / cm 3, the In _x Al _1-x N buffer layer 110 is It does not contribute to increasing the background electron concentration.

As a means of evaluating the quality of a GaN thin film, the x-ray diffraction curve half-width is often used. Since the half width of the (002) x-ray diffraction curve indicates the density of dislocation defects present in the thin film, it can be used as an index indicating direct thin film crystallinity. The smaller the half-width of the x-ray diffraction curve means that the crystallinity is better.

3 and 4 are comparative graphs of X-ray diffraction measurements of a nitride semiconductor thin film using a conventional GaN buffer layer and a nitride semiconductor thin film using an In _x Al _1-x N buffer layer according to the same conditions, respectively. It is a graph comparing half width of.

X-ray diffraction measurements of the nitride semiconductor thin film (a) using the conventional GaN buffer layer formed in the same conditions of Figure 3 and the nitride semiconductor thin film (b) using the In _x Al _1-x N buffer layer of the present invention As a comparative graph performed, the measurement result of the nitride semiconductor thin film (b) using the InAlN buffer layer rather than the nitride semiconductor thin film (a) using the GaN buffer layer is as shown.

FIG. 4 shows that the nitride semiconductor thin film (a) using the GaN buffer layer has a half width larger than that of the nitride semiconductor thin film (b) using the InAlN buffer layer, as shown in FIG. 4. You can see the big picture. That is, it can be seen that the crystallinity is better than that of the nitride semiconductor thin film (a) using the GaN buffer layer of the nitride semiconductor thin film (b) using InAlN as the buffer layer.

Accordingly, the nitride semiconductor device according to the present invention uses an InAlN buffer layer to effectively relieve stress between the hetero substrate and the nitride semiconductor thin film, thereby increasing the mobility of the carrier, thereby enabling low driving voltage and high luminous efficiency. There is this.

Claims (4)

In forming a nitride semiconductor thin film on a dissimilar substrate, And forming an In _x Al _1-x N (0 <x ≤ 1) buffer layer on the substrate. The method of claim 1, wherein the In _x Al _1-x N buffer layer is In _x Al _1-x N and a linear or nonlinear composition of In _x Al _1-x N grown in the same composition ratio within the range of 0 <x ≤ 1. A nitride semiconductor device comprising a picture In _x Al _1-x N. The nitride semiconductor device according to claim 1, wherein the buffer layer is formed at a temperature in the range of 300 to 900 ° C. The method according to claim 1, nitride between said buffer layer In _x Al _1-x N and the nitride semiconductor thin film characterized by forming an additional buffer layer _{In x Al y Ga 1-xy} N (0 ≤ x + y ≤1) semiconductor device.