Visible light communication LED having a spiral inductance coil and a circle core and preparation method thereof

Abstract

A visible light communication LED having a spiral inductance coil and a circular core is provided, comprising a sapphire substrate provided with a positive electrode welding spot and a negative electrode welding spot, and a plurality of LED cores deposited on the sapphire substrate. The negative electrode of a former core is connected with the positive electrode of a latter core, and the positive electrode of the first core and the negative electrode of the last core are respectively connected to the positive electrode welding spot and the negative electrode welding spot on the substrate. According to the present invention, each of the LED cores is surrounded by a spiral inductance coil, and a pin of one end of the spiral inductance coil is connected via a connecting wire with the negative electrode of an adjacent LED core, while the other end is directly connected with the positive electrode of the LED core that is surrounded by the spiral inductance coil.

Claims

1. A visible light communication LED, comprising a sapphire substrate, a plurality of LED cores deposited on the sapphire substrate and connected to each other in series, wherein each of the plurality of LED cores includes a negative electrode and a positive electrode, and a plurality of spiral inductance coils disposed on the sapphire substrate, wherein each of the plurality of spiral inductance coils surrounds one of the plurality of LED cores and includes one end connected to the positive electrode of the one of the plurality of LED cores and another end connected to a negative electrode of the other one of the plurality of LED cores, which is next to the one of the plurality of LED cores.

2. The visible light communication LED according to claim 1, comprising sixteen LED cores which are configured to form a 44 matrix.

3. The visible light communication LED according to claim 1, wherein the LED core comprises a GaN/InGaN epitaxial wafer, a transparent conductive layer is provided on a p-type layer of the epitaxial wafer, an annular positive electrode is provided on the transparent conductive layer, and the core is divided into an inner annular emission region, a middle annular emission region and an outer annular emission region by the annular positive electrode.

4. The visible light communication LED according to claim 3, wherein the GaN/InGaN epitaxial wafer comprises from its bottom to top a buffer layer, an n-type layer, a multiple quantum well layer, and a p-type layer.

5. The visible light communication LED according to claim 1, wherein the spiral inductance coil has an inductance value in a range of 20 nH-200 nH.

6. The visible light communication LED according to claim 1, wherein the spiral inductance coil has an outer diameter of 300 m300 m, an inner diameter of 170 m170 m, a line width of 5 m, and a line distance of 10 m.

Description

BRIEF DESCRIPTION TO THE DRAWINGS

(1) FIG. 1 shows a schematic view of the structure of the visible light communication LED device of Example 1 according to the present invention.

(2) FIG. 2 shows a top view of the structure of a LED core.

(3) FIG. 3 shows a side view of the structure of a LED core.

LIST OF REFERENCE NUMBERS

(4) 1: Sapphire substrate of the epitaxial wafer 2: LED core 3: Spiral inductance coil 4: Positive electrode welding spot of the device 5: Negative electrode welding spot of the device 6: Silicon dioxide insulation protective layer 7: Connecting wire between the spiral inductance coil and the negative electrode of the core 8: Annular positive electrode 9: Transparent conductive layer 10: Annular negative electrode 11: Inner annular emission region 12: Middle annular emission region 13: Outer annular emission region 14: Buffer layer of the epitaxial wafer 15: N-type layer of the epitaxial wafer 16: Multiple quantum well layer of the epitaxial wafer 17: P-type layer of the epitaxial wafer 18: Pin of the outer end of the spiral inductance coil 19: Entrance of the connecting wire 20: Exit of the connecting wire

DETAILED DESCRIPTION OF THE INVENTION

(5) The present invention will be described in conjugation with embodiments and figures.

Example 1

(6) FIG. 1 shows a visible light communication LED having a spiral inductance coil and a circular core, comprising a sapphire substrate 1 provided with a positive electrode welding spot 4 and a negative electrode welding spot 5, and a plurality of LED cores 2 deposited on the sapphire substrate. The negative electrode 10 of a former core is connected with the positive electrode 8 of a latter core, and the positive electrode of the first core and the negative electrode of the last core are respectively connected to the positive electrode welding spot and the negative electrode welding spot on the substrate. Each of the LED cores is surrounded by a spiral inductance coil 3, and one end of the spiral inductance coil is connected with the negative electrode of the LED core that is surrounded by this spiral inductance coil, while the other end of this spiral inductance coil is connected with the positive electrode of an adjacent LED core.

(7) The visible light communication LED of the present example comprises sixteen LED cores which are configured to form a 44 matrix.

(8) The sixteen LED cores, each having a voltage of 3V and through-current of 5-30 mA, making a total voltage of 163V=48V, are connected in series. Although this configuration increases resistance R of the whole device, it also reduces capacity C of the whole device to the same proportion, and reduces time constant in the circuit. In comparison with a core of a single annular structure, this configuration provides an increased response frequency and at the same time facilitates arrangement and manufacturing of the spiral inductance.

(9) The LED core comprises a GaN/InGaN epitaxial wafer. A transparent conductive layer 9 is provided on a p-type layer of the epitaxial wafer. An annular positive electrode 8 is provided on the transparent conductive layer. The core is divided into an inner annular emission region 11, a middle annular emission region 12 and an outer annular emission region 13 by the annular positive electrode.

(10) The GaN/InGaN epitaxial wafer comprises from its bottom to top a buffer layer 14, an n-type layer 15, a multiple quantum well layer 16, and a p-type layer 17.

(11) The spiral inductance coil has an inductance value in the range of 20 nH-200 nH.

(12) It has been demonstrated by experiments of the present invention that in a circuit having the frequency of 10 MHz-100 MHz, adding an inductance of 20 nH-200 nH can effectively reduce impedance in the circuit, and increase response frequency of the visible light emitting device. Further, as the frequency increases, the inductance required by the resonance decreases gradually.

(13) The spiral inductance coil has the outer diameter of 300 m300 m, the inner diameter of 170 m170 m, the line width of 5 m, and the line distance of 10 m.

Example 2

(14) A preparation method for a visible light communication LED having a spiral inductance coil and a circular core is provided, comprising:

(15) growing a plurality of independent GaN/InGaN epitaxial wafers on a sapphire substrate, and forming a positive electrode welding spot and a negative electrode welding spot on the substrate;

(16) depositing a transparent conductive layer on a p-type layer of the epitaxial wafer by magnetron sputtering, and forming N annular positive electrodes on the transparent conductive layer, thereby providing a plurality of LED cores;

(17) connecting the negative electrode of a former core with the positive electrode of a latter core, and connecting the positive electrode of the first core and the negative electrode of the last core respectively to the positive electrode welding spot and the negative electrode welding spot on the substrate, thereby allowing the plurality of LED cores to form a matrix, and connecting the plurality of LED cores in series;

(18) evaporate plating a spiral inductance coil at the periphery of each of the LED cores;

(19) connecting one end of the spiral inductance coil directly with the negative electrode of the LED core that is surrounded by this spiral inductance coil, and connecting a pin of the other end of this spiral inductance coil with the positive electrode of an adjacent LED core.

(20) Growing a GaN/InGaN epitaxial wafer on a sapphire substrate comprises:

(21) using trimethyl gallium, trimethyl indium and NH.sub.3 as the Ga source, the In source and the N source respectively, and SiH.sub.4 and CP.sub.2Mg as the n-type doping source and the p-type doping source,

(22) performing heat treatment at 1100 C. in a H.sub.2 atmosphere on the sapphire substrate,

(23) growing a buffer layer at 550 C.,

(24) heating to 1070 C. to grow a n-type layer of the epitaxial wafer,

(25) cooling to 760 C. to grow a quantum well layer,

(26) heating to 970 C. to grow a p-type layer, and

(27) annealing at 750 C. in a N.sub.2 atmosphere.

(28) Evaporate plating a spiral inductance coil at the periphery of a core comprises:

(29) sputtering a layer of metal as a marker at the back side of the substrate according to a pre-determined position where the spiral inductance coil is to be installed;

(30) sputtering a seed layer at the front side of the substrate, applying a photoresist, and evaporate plating the spiral inductance coil and an annular electrode after exposing and developing;

(31) removing the photoresist, and removing the seed layer by dry etching;

(32) sputtering another seed layer at the front side of the substrate, applying a photoresist, plating a pin of the spiral inductance coil after exposing and developing, removing the photoresist, and removing the seed layer by dry etching;

(33) applying an insulation protective layer while keeping the pin of the inductance coil uncovered; and

(34) evaporate plating a metal connecting wire on the insulation protective layer, to respectively connect with the negative electrode of a former LED core and a pin of an outer end of a latter spiral inductance coil.

(35) The insulation protective layer is a silicon dioxide insulation protective layer.