JP2010283125A - Light emitting diode - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light emitting diode capable of sufficiently exhibiting the light emitting capability of an element. <P>SOLUTION: The light emitting diode includes an n-type nitride semiconductor layer laminated on an upper surface of a sapphire substrate via a buffer layer, a p-type nitride semiconductor layer laminated on the n-type nitride semiconductor layer, an n electrode connected to the n-type nitride semiconductor layer, and a p electrode connected to the p-type nitride semiconductor layer, wherein the n-type nitride semiconductor layer is laminated on the buffer layer so as to cover a part of a side wall of the sapphire substrate, the n electrode is arranged on the n-type nitride semiconductor layer laminated on the side wall of the sapphire substrate, the p-type nitride semiconductor layer is laminated on the n-type nitride semiconductor layer so as to cover a side wall portion of the n-type nitride semiconductor layer, and the p electrode is arranged on the p-type nitride semiconductor layer laminated on the side wall portion of the n-type nitride semiconductor layer. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates generally to light emitting diodes (LEDs), and more particularly to electrode arrangements for light emitting diodes.

  A light emitting diode is a semiconductor element that emits light when a voltage is applied in the forward direction, and the principle of light emission utilizes an electroluminescence (EL) effect. The light emitting diode has a semiconductor PN junction structure, and light emission is performed by directly converting the energy of electrons into light energy.

  Holes and electrons injected into the semiconductor from the p-electrode and n-electrode flow through different energy bands (a valence band and a conduction band) and recombine beyond the forbidden band near the PN junction. During recombination, energy corresponding to the forbidden bandwidth (band gap) is emitted as light.

  The wavelength of the emitted light is determined by the band gap of the material and is basically a single color with a low degree of freedom, but the white light is extracted by applying the blue light emitted from the blue light emitting diode to the phosphor. Recently, it has been used as a backlight light source for liquid crystal display devices.

  Furthermore, since it consumes significantly less power than light emitters such as light bulbs and fluorescent lamps and has a long service life, it is actively used as a traffic light or household lighting. Recently, it is also used in automobile headlights.

JP 2004-111909 A

  The electrode arrangement of a conventional light emitting diode is generally such that an n electrode is arranged on the n type nitride semiconductor layer and a p electrode is arranged on the p type nitride semiconductor layer. However, in such an electrode arrangement, there is a problem that light is blocked by the electrode and the light emission ability is not sufficiently exhibited.

  This invention is made | formed in view of such a point, The place made into the objective is providing the light emitting diode which can fully exhibit the light emission capability.

  According to the present invention, an n-type nitride semiconductor layer stacked on a top surface of a sapphire substrate via a buffer layer, a p-type nitride semiconductor layer stacked on the n-type nitride semiconductor layer, and the n-type nitride And a p-electrode connected to the p-type nitride semiconductor layer, wherein the n-type nitride semiconductor layer is a part of a side wall of the sapphire substrate. The n-electrode is disposed on the n-type nitride semiconductor layer stacked on the sidewall of the sapphire substrate, and the p-type nitride semiconductor layer is the n-type The p-type nitride semiconductor is stacked on the n-type nitride semiconductor layer so as to cover the side wall of the nitride semiconductor layer, and the p-electrode is stacked on the side wall of the n-type nitride semiconductor layer. There is provided a light emitting diode characterized in that it is disposed on a layer.

  According to the present invention, the n electrode and the p electrode are respectively disposed on the side wall portion of the n-type nitride semiconductor layer and the side wall portion of the p-type nitride semiconductor layer stacked on the side wall of the sapphire substrate. The light emission ability of the light emitting diode can be sufficiently exhibited without hindering light emission.

It is a perspective view of LED concerning this invention embodiment. It is a drive circuit diagram of LED concerning this invention embodiment. It is explanatory drawing for demonstrating the manufacturing method of LED.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Referring to FIG. 1, a perspective view of a light emitting diode (LED) 2 according to an embodiment of the present invention is shown. The light emitting diode (LED) 2 is formed by laminating a nitride semiconductor layer on a sapphire substrate 4.

  With reference to FIG. 3, the manufacturing method of LED2 is demonstrated. First, a rectangular groove 4 a is formed in the sapphire substrate 4. The rectangular groove 4a can be formed, for example, by laser processing that irradiates the sapphire substrate 4 with a laser beam having a wavelength that is absorptive with respect to the sapphire substrate 4.

  Next, a low-temperature buffer layer 6 is laminated on the sapphire substrate 4. As the low-temperature buffer layer 6, gallium nitride (GaN) or aluminum nitride (AlN) is suitable. In this embodiment, GaN is grown on the sapphire substrate 4 at a low temperature of about 500 ° C.

  An n-type gallium nitride layer (GaN layer) 8 is stacked on the low-temperature buffer layer 6, and a p-type gallium nitride layer 10 is stacked on the n-type gallium nitride layer 8. In the present embodiment, the n-type gallium nitride layer 8 and the p-type gallium nitride layer 10 are grown by MOCVD.

  The p-type gallium nitride layer 10 is formed by doping magnesium (Mg) into a gallium nitride source gas to form an n-type gallium nitride layer, and then heating to about 500 ° C. in a nitrogen atmosphere. The type gallium nitride layer 10 can be obtained.

  Thus, after each layer 6, 8, 10 is laminated | stacked on the sapphire substrate 4, the sapphire substrate 4 is cut | disconnected by the A line shown in FIG. For this cutting, it is possible to use cutting with a cutting blade or laser processing with a laser beam having a wavelength that is absorptive with respect to the sapphire substrate 4. The cutting in the direction orthogonal to the rectangular groove 4a may be performed at a predetermined interval (depth length of the LED 2) using a cutting blade or a laser beam.

  After the laminate is cut along the line A in FIG. 3, the side wall portion of the p-type gallium nitride layer 10 is obtained by grinding the sapphire substrate 4 and the p-type gallium nitride layer 10 on one side to a predetermined depth and then polishing. And the side wall of the n-type gallium nitride layer 8 is exposed.

  Next, as shown in FIG. 2, a p-electrode 12 is disposed on the side wall of the p-type gallium nitride layer 10 that has not been ground / polished, and the n-type gallium nitride layer 8 exposed by grinding / polishing is formed on the side wall. An n-electrode 14 is provided.

  As shown in FIG. 2, the driving method of the light emitting diode (LED) 2 of the present embodiment is such that the p-electrode 12 is connected to the positive side of the DC power source 16 via the resistor R, and the n-electrode 14 is connected to the negative side of the DC power source 16. The LED 2 is driven by applying a predetermined voltage.

  As a result, electrons injected from the n-electrode 14 flow through the conduction band of the n-type GaN layer 8, and holes injected from the p-electrode 12 flow through the valence band of the p-type GaN layer 10 to form a pn junction. Recombine across the forbidden band in the vicinity.

  Upon recombination, energy substantially corresponding to the forbidden bandwidth (band gap) is emitted as photons, that is, light. Since the band gap of gallium nitride is about 3.4 electron volts (eV), the LED 2 of this embodiment emits ultraviolet light having a center wavelength of about 360 nm.

  In the present embodiment, as shown in FIG. 2, light is emitted from the LED 2 in the direction of arrow A, but the p-electrode 12 and the n-electrode 14 are p-type GaN layers 10 stacked on the side wall of the sapphire substrate 4. Therefore, the electrodes 12 and 14 do not hinder light emission, and the light emission capability of the LED 2 can be fully exhibited.

2 Light emitting diode (LED)
4 Sapphire substrate 6 Low-temperature buffer layer 8 n-type GaN layer 10 p-type GaN layer 12 p-electrode 14 n-electrode

Claims (1)

An n-type nitride semiconductor layer stacked on the upper surface of the sapphire substrate via a buffer layer, a p-type nitride semiconductor layer stacked on the n-type nitride semiconductor layer, and connected to the n-type nitride semiconductor layer A light emitting diode comprising an n electrode formed and a p electrode connected to the p-type nitride semiconductor layer,
The n-type nitride semiconductor layer is laminated on the buffer layer so as to cover a part of the side wall of the sapphire substrate, and the n-type nitride semiconductor layer is laminated on the side wall of the sapphire substrate. Arranged in
The p-type nitride semiconductor layer is stacked on the n-type nitride semiconductor layer so as to cover the sidewall portion of the n-type nitride semiconductor layer, and the p-electrode is formed on the sidewall of the n-type nitride semiconductor layer. A light emitting diode, wherein the light emitting diode is disposed on the p-type nitride semiconductor layer stacked on the portion.

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