Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
  • H01L33/02—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies
  • H01L33/26—Materials of the light emitting region
  • H01L33/30—Materials of the light emitting region containing only elements of Group III and Group V of the Periodic Table
  • H01L33/32—Materials of the light emitting region containing only elements of Group III and Group V of the Periodic Table containing nitrogen
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
  • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
  • H01L33/02—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies

Definitions

• the present invention relates to a light emitting device, and particularly,, to a light emitting device having an improved operational reliability and a manufacturing method of the same. More particularly, the present invention relates to a light emitting device providing an improved operational reliability by a structure in which it is protected from static electricity and its breakdown voltage is increased, and a manufacturing method of the same.
• a light emitting device is a kind of semiconductor device that converts electrical energy into light by using a characteristic of a compound semiconductor.
• the light emitting device is widely used for home appliances, a remote controller, an electronic display board, a display device, a variety of automation apparatuses, and the like.
• a typical example of the light emitting ' device is a light emitting diode (LED) .
• the LED is operated in such a way that electrons and holes are recombined with each other while moving through a PN-junction by a forward voltage applied to a semiconductor of a specific chemical element, and the fall of an energy level due to the electron-hole recombination causes light emission to occur.
• the LED is generally manufactured to have a very small size of 0.25 mm 2 and is fixed using a mold.
• the LED has lead frames for applying a source voltage thereto and is mounted on a printed circuit board (PCB) .
• PCB printed circuit board
• a typical example of a LED package is a plastic LED package of 5mm (T 1 3/4) , and a variety of LED packages are being developed in specific application fields. Meanwhile, with the trend of miniaturization and slimness of an information communication device, various components of the device such as a resistor, a condenser and a noise filter are being further miniaturized. In accordance with this trend, the LED is also manufactured in the form of a surface mounted device (SMD) so as to be directly mounted on a PCB .
• SMD surface mounted device
• a color of light emitted from the LED is determined according to its wavelength obtained depending on a combination of elements constituting a semiconductor chip. Recently, following red and green LEDs a blue LED has been developed, and the LED is being more widely used in various technical fields. For example, the LED is used as a white-light lamp or a light source for a display device. Moreover, the LED is further improved in its light luminance and thus is also used for an electronic display board and a camera of a mobile phone.
• a general blue LED is constructed to include a sapphire substrate, a buffer layer formed on the sapphire substrate, an undoped GaN layer formed on the buffer layer, an N-type GaN layer formed on the undoped GaN layer, an active layer formed on the N-type GaN layer, and a P-type GaN layer formed on the active layer.
• the active layer is a semiconductor layer made of luminescent material such as InGaN, and serves as a light- emitting region.
• the P-type GaN layer is in contrast with the N-type GaN layer.
• the electrons and the holes are then recombined with each other in the active layer to thereby cause light emission.
• the abovementioned light emitting device has a drawback in that its reliability is degraded when its light luminance is improved, and vice versa.
• the light emitting device must have a high reliability so as to be used for a high-luminance electronic display board and a mobile phone.
• each layer formed in the device must be improved in crystallinity .
• the light emitting device has limitations in reliability improvement because it has structural limitations for emitting light of a desired wavelength.
• an electrostatic discharge (ESD) generated from electronic components near the light emitting device or from a human body is applied to the light emitting device, the light emitting device (specifically, its active layer) is frequently damaged by the applied ESD.
• ESD electrostatic discharge
• an additional diode such as a Zener diode may be provided at a power input terminal of the light emitting device.
• this additional diode undesirably causes an increase in the manufacturing cost of the light emitting device.
• the present invention is directed to a light emitting device and a manufacturing method thereof that substantially obviate one or more of the problems due to limitations and disadvantages of the related art.
• An object of the present invention is to provide a light emitting device having an improved operational reliability and a manufacturing method thereof.
• Another object of the present invention is to provide a light emitting device having an improved light luminance without degradation in its reliability and a manufacturing method thereof.
• a further object of the present invention is to provide a light emitting device that can be simply mounted on a desired apparatus because a separate diode need not be provided at its power input terminal and a manufacturing method thereof.
• a light emitting device includes: a substrate; a gallium nitride layer provided above the substrate; an N-type gallium nitride layer provided above the gallium nitride layer; at least one In x Ga ⁇ _ x N/In y Ga ⁇ -. y N multi- layer (0 ⁇ x,y ⁇ l) provided above the N-type gallium nitride layer, x being different from y; and a P-type gallium nitride layer provided above the In x Ga ⁇ - ⁇ N/In y Ga ⁇ _yN multi-layer.
• a light emitting device in another aspect of the present invention, includes: a first gallium nitride layer; a second gallium nitride layer; an active layer formed between the first gallium nitride layer and the second gallium nitride layer; and a multi-layer formed between the second gallium nitride layer and the active layer to intercept an applied electrostatic discharge.
• a method for manufacturing a light emitting device includes the steps of: forming a buffer layer above a substrate; forming an N- type gallium nitride layer above the buffer layer; forming a multi-layer above the N-type gallium nitride layer, the multi-layer including layers of different ' growth temperatures; forming an active layer above the multi-layer; and forming a P-type gallium nitride layer above the active layer.
• the present invention makes it possible to improve the breakdown voltage characteristic and reliability of a light emitting device. Also, the present invention makes it ' possible to protect a light emitting device (specifically, its active layer) from an electrostatic discharge and a high voltage applied thereto. Furthermore, the present invention makes it possible to improve the operational reliability of a light emitting device without degradation in the light efficiency thereof. Moreover, the present invention makes it possible to reduce the manufacturing cost and volume of a light emitting device package because a separate diode for intercepting an applied ESD need not be provided at a power input terminal of the light emitting device.
• FIGs 1 to 4 are sectional ⁇ views illustrating a method for manufacturing a light emitting device according to an embodiment of the present invention.
• FIG. 5 is a sectional view of a light emitting device according to an embodiment of the present invention.
• FIG. 6 is an AFM image of a related art N-type GaN layer.
• FIG. 7 is an AFM image of a multi-layer according to the present invention.
• FIGs. 1 to 4 are sectional views illustrating a method for manufacturing a light emitting device according to an embodiment of the present invention
• FIG. 5 is a sectional view of a light emitting device according to an embodiment of the present invention.
• the inventive manufacturing method for the light emitting device will now be described with reference to FIGs. 1 to 5. Referring first to FIGs. 1 and 2, a GaN buffer layer 201 is formed on a sapphire substrate 200 at a predetermined temperature and then a slow-growth GaN layer 203 is formed on the buffer layer 201.
• the buffer layer 201 may be grown at 500-600 °C .
• the GaN layer 203 is formed to prevent the defects of the buffer layer 201 from being transmitted to an undoped GaN layer (see 205 of FIG. 3) that is to be formed on the GaN layer 203 and to a nitride layer near the undoped GaN layer
• the undoped GaN 205 is grown on the GaN layer 203 at a predetermined temperature and then a doped N-type GaN layer 207 is formed on the undoped GaN layer
• the undoped GaN layer 205 may . be grown at
• an InGaN/InGaN multi-layer 209 for protecting the light emitting device from an ESD to thereby improve the operational reliability of the device is formed on the doped N-type GaN layer 207 prior to forming an active layer (see 211 of FIG. 5) .
• the InGaN/InGaN multi-layer 209 is constructed to include a first InGaN layer 209a formed on the doped N-type GaN layer 207 at a high temperature, and a second InGaN layer
• the first InGaN layer 209a may be grown to a thickness of 1-3000 A at about 900 °C
• the second InGaN layer 209b may be grown to a thickness of 1-3000 at about 800 °C.
• the first and second InGaN layers 209a and 209b each may be grown in plurality.
• the second InGaN layer 209b may be first formed on the doped N-type GaN layer 207 and then the first InGaN layer 209a may be formed on the second InGaN layer 209b.
• the InGaN/InGaN multi-layer 209 may be formed to have a super lattice structure.
• a method for forming the InGaN/InGaN multi-layer 209 will now be described in detail.
• the InGaN/InGaN multi-layer 209 is grown using an alkyl source including TMGa and TMIn and a hydride gas including NH 3 and N 2 .
• TMGa is 50-500 ⁇ mol
• TMIn is 25-500 ⁇ mol
• NH 3 and N 2 are 1-100 liter.
• the InGaN/InGaN multi-layer 209 is grown with H 2 being removed.
• H 2 is not included in the InGaN/InGaN multi-layer 209.
• the first and second InGaN layers 209a and 209b have different In-Ga ratios because they are grown at different temperatures.
• a layer contains less In when it is grown at a higher temperature.
• the first InGaN layer 209a contains less In than the second InGaN layer 209b.
• In content of the layers 209a and 209b can be expressed as Equation (1) below.
• the InGaN/InGaN multi-layer 209 has a plurality of hexagonal pits (see 10 of FIG. 7) formed thereon due to dislocation and defects resulting from the doped N-type GaN layer 207 and defects resulting from the super lattice structure .
• the number, of the hexagonal pits 10 is preferably 50 or less per area of 5 ⁇ mX-5 ⁇ m.
• the hexagonal pits 10 primarily reduce a current when a reverse voltage is applied to the light emitting device, and thus protects the active layer 211 from a high voltage applied thereto. Also, the hexagonal pits 10 can provide a bypath through which a current flows, thereby preventing the current from flowing through the active layer 211.
• the hexagonal pits 10 serves as a kind of capacitor. That is, the capacitor (the hexagonal pits 10) is charged with a forward voltage when a forward voltage is applied to the light emitting device, and is charged with a reverse voltage when a reverse voltage due to an ESD is instantaneously applied thereto. Accordingly, a high ESD can be prevented from being applied to the active layer 211.
• the active layer 211 having an InGaN/InGaN structure of a multi-quantum well structure is grown on the InGaN/InGaN multi-layer 209.
• the active layer may be grown at about 600-800 °C.
• a P-type GaN layer 220 doped with impurities of Mg is grown on the active layer 211.
• FIG. 6 is an AFM image of a related art N-type GaN layer
• FIG. 7 is an AFM image of a multi-layer according to the present invention. Referring to FIGs.
• a plurality of hexagonal pits 10 are formed on the InGaN/InGaN multi-layer 209.
• the hexagonal pits 10 serve to remove a reverse current applied to the light emitting device or to provide a bypath through which a current flows, thereby preventing the active layer 211 being damaged by an externally-applied ESD. Consequently, the light emitting device can be protected from an externally-applied high voltage.
• Table 1 below compares an anti-ESD durability of the inventive light emitting device with that of the related art light emitting device. Table 1
• the inventive light emitting device equipped with the InGaN/InGaN multi-layer 209 can normally operate even when an about-20-time higher revere voltage is applied thereto.
• the present invention increases a breakdown voltage of the light emitting device and thus prevents an externally-applied ESD from affecting the light emitting device.
• the present invention can provide a high breakdown voltage of the light emitting device by merely forming the InGaN/InGaN multi-layer 209 in the device.
• InGaN/InGaN multi-layer 209 is maintained at a yellow band intensity/N-doped GaN intensity ratio of 0.4 or below, whereby the operational reliability of the light emitting device can be further improved.
• the present invention can improve an anti-ESD durability of a light emitting device while maintaining the light efficiency of the device. Also, .the present invention can improve the operational reliability of a light emitting device while maintaining the light efficiency of the device. Furthermore, the inventive light emitting device can stably operate even when a high voltage is applied thereto so as to increase its light luminance . Moreover, the present invention can reduce the manufacturing cost of a light emitting device package because a separate diode for intercepting an applied ESD need not be provided at a power input terminal of the light emitting device .

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• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Computer Hardware Design (AREA)
• Microelectronics & Electronic Packaging (AREA)
• Power Engineering (AREA)
• Led Devices (AREA)
• Semiconductor Lasers (AREA)

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• 2004
  • 2004-04-13 KR KR1020040025310A patent/KR100678854B1/ko not_active IP Right Cessation
• 2005
  • 2005-04-12 CA CA2528720A patent/CA2528720C/en not_active Expired - Fee Related
  • 2005-04-12 WO PCT/KR2005/001045 patent/WO2005101534A1/en active Application Filing
  • 2005-04-12 DE DE112005000703.0T patent/DE112005000703B4/de active Active
  • 2005-04-12 JP JP2006516972A patent/JP2006527503A/ja active Pending
  • 2005-04-12 CN CNA2005800003687A patent/CN1788360A/zh active Pending
  • 2005-04-12 US US10/564,486 patent/US8134167B2/en not_active Expired - Fee Related

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