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  Silicon nitride layer for light emitting device, light emitting device using the same, and method of forming silicon nitride layer for light emitting deviceRelated Patent Categories: Active Solid-state Devices (e.g., Transistors, Solid-state Diodes), Incoherent Light Emitter Structure, With HeterojunctionThe Patent Description & Claims data below is from USPTO Patent Application 20080093609. Brief Patent Description - Full Patent Description - Patent Application Claims
BACKGROUND ART [0001] 1. Field of the Invention [0002] The present invention relates to a silicon nitride layer for a light emitting device, light emitting device using the same, and method of forming the silicon nitride layer for the light emitting device, and more specifically, to a silicon nitride layer for a light emitting device, which includes a silicon nitride matrix and silicon nanocrystals formed in the silicon nitride matrix. [0003] 2. Description of Related Art [0004] In order to obtain a light emitting effect using silicon as an indirect bandgap semiconductor, it is necessary to provoke a quantum confinement effect due to fine structures (Refer to Light Emission in Silicon: From Physics to Devices, edited by D. J. Lockwood (Academic Press, San Diego, 1998), Chap. 1). [0005] The quantum confinement effect involves forming fine crystalline or amorphous silicon structures having a size of several nm or less (e.g., quantum wells, quantum wires, and quantum dots) using a matrix or barrier formed of a material that has a larger energy gap than bulk silicon. In this case, as the fine structures become smaller, the wavelength of light they emit becomes shorter. Among the examples of the fine structures, the quantum dot nanostructures exhibit a particularly high quantum yield. [0006] In recent years, research for applications of silicon fine structures formed in a silicon oxide matrix to a silicon light emitting device has progressed (Refer to N. Lalic and J. Linnros, J. Lumin. 80, 263 (1999), S.-H. Choi and R. G. Elliman, Appl. Phys. Lett. 75, 968 (1999)). However, the silicon fine structures were obtained by annealing Si-rich silicon oxide at a high temperature of about 1100 ? or higher for about 30 minutes to 2 hours. [0007] The above-described method involves additional processes and takes much time. Also, problems caused by the high-temperature annealing process remain unsolved. For these reasons, it is difficult to directly apply conventional semiconductor processes to the method. [0008] Moreover, in manufacturing a light emitting device using silicon oxide, it is required to form a matrix or barrier to a very small thickness because of a high application voltage. SUMMARY OF THE INVENTION [0009] The present invention is directed to a silicon nitride layer for a light emitting device, which is obtained in relatively simple manners. For example, silicon nanocrystals are directly grown during formation of the silicon nitride layer. [0010] Also, the present invention is directed to a method of directly forming good, uniform silicon nanocrystals at a low temperature. [0011] One aspect of the present invention is to provide a silicon nitride layer for a light emitting device, which includes a silicon nitride matrix; and silicon nanocrystals formed in the silicon nitride matrix. [0012] Here, a silicon nanocrystal structure generically refers to a quantum dot nanostructure in which nano-sized crystalline silicon particles are scattered in a matrix. [0013] Typically, the silicon nanocrystal structure has a spherical shape but not limited thereto. [0014] In order to apply the silicon nanocrystal structure to the light emitting device, the silicon nanocrystals have a diameter of about 2 to 7 nm and a density of 10.sup.11 to 10.sup.13/cm.sup.2. [0015] In the present invention, the thickness of the silicon nitride layer including quantum dot nanostructures may be changed according to the type of device or desired emission extent but may be about 3 to 100 nm. [0016] Another aspect of the present invention is to provide a method of forming a silicon nitride layer for a light emitting device. The method includes loading a substrate for forming the silicon nitride layer into a chamber of a layer forming system; and growing a silicon nitride matrix and simultaneously forming silicon nanocrystals in the silicon nitride matrix using a silicon source gas and a nitrogen source gas. [0017] Here, the layer forming system should not be construed as limited to the embodiments set forth herein and refers to any system used for forming a layer as known in the art. Preferably, the layer forming system refers to a system that makes use of a chemical vapor deposition (CVD) process, a molecular beam epitaxy (MBE) process, or an ion implantation process. The MBE process employs a lump of solid silicon as a silicon source for silicon nitride, the ion implantation process employs proton or electron silicon particles as the silicon source, and the CVD process employs a silicon source gas, such as SiCl.sub.4, SiHCl.sub.3, SiH.sub.2Cl.sub.2, SiH.sub.4, and Si.sub.2H.sub.6 as the silicon source. In this case, the CVD process may be, but not limited to, an atmospheric pressure CVD (APCVD) process, a low-pressure CVD (LPCVD) process, a plasma enhanced CVD (PECVD) process, a metal organic CVD (MOCVD) process, or a thermal CVD process. Preferably, the CVD process is a PECVD process, which is in common use during manufacture of silicon devices. [0018] Meanwhile, silane gas may be used as a silicon source for silicon nitride, and a gas containing nitrogen atoms, for example, nitrogen gas or ammonia gas, may be mainly used as a nitrogen source for the silicon nitride. [0019] The silicon source gas and the nitrogen source gas may be supplied to the layer forming system in a ratio of 1:1000 to 1:4000 so that the silicon nitride layer for the light emitting device can be grown at a growth rate of 1.3 to 1.8 nm/min. Preferably, the silicon source gas and ammonia gas may be supplied to a thin-film growth system in a ratio of 1:1 to 1:5 so that the silicon nitride layer for the light emitting device can be grown at a growth rate of 5 to 10 nm/min. [0020] An MBE process uses solid silicon, an ion implantation process uses Si particles, and a CVD or PECVD process uses SiCl.sub.4, SiHCl.sub.3, SiH.sub.2Cl.sub.2, SiH.sub.4, or Si.sub.2H.sub.6 as a silicon source. Meanwhile, it is desirable to use a source gas containing H that forms silicon crystals. [0021] Another aspect of the present invention is to provide a silicon light emitting device, which is manufactured using a silicon nitride layer including a silicon nitride matrix and silicon nanocrystals formed in the silicon nitride matrix. Meanwhile, during the formation of silicon nitride, an emission wavelength can be appropriately controlled to a desired wavelength according to the flow rates of a silicon source (e.g., silane) and a nitrogen source (e.g., nitrogen or ammonia). The silicon light emitting device may be, for example, a p-type semiconductor/insulator/n-type semiconductor (PIN) structure, a metal/insulator/semiconductor (MIS) structure, or a conductive polymer/insulator/semiconductor junction structure. In this case, the insulator refers to a silicon nitride layer according to the present invention. BRIEF DESCRIPTION OF THE DRAWINGS Continue reading... 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