LIGHT EMITTING DIODE STRUCTURE

A light emitting diode structure includes a metal reflective layer, a first transparent electrically-conductive layer, a dielectric layer, second transparent electrically-conductive layers, a first type semiconductor layer, an active layer and a second type semiconductor layer. The metal reflective layer has first concave sections. The first transparent electrically-conductive layer is conformally formed over the first concave sections of the metal reflective layer. The dielectric layer is formed over the first transparent electrically-conductive layer and has through holes to expose the first transparent electrically-conductive layer. The second transparent electrically-conductive layers are formed over the dielectric layer, and connected with the first transparent electrically-conductive layer via the through holes. Each second transparent electrically-conductive layer is connected to the first transparent electrically-conductive layer to form a T-shaped cross section in each first concave section.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to China Application Serial Number 202110177331.2, filed Feb. 9, 2021, which is herein incorporated by reference in its entirety.

BACKGROUND

Field of Invention

The present disclosure relates to a light emitting diode structure.

Description of Related Art

Light emitting diode is a light-emitting element made of semiconductor material that can convert electrical energy into light. It has the advantages of small size, high energy conversion efficiency, long life, power saving, etc., so it can be widely used as light source in various electronic applications.

Light emitting diodes with metal reflective layers often fail to achieve proper light extraction efficiency due to structural factors. In view of this, suppliers need various solutions to improve the light reflection efficiency of the metal reflective layer so as to achieve better light extraction efficiency.

SUMMARY

One aspect of the present disclosure is to provide a light emitting diode structure, which includes a metal reflective layer, a first transparent electrically-conductive layer, a dielectric layer, a plurality of second transparent electrically-conductive layers, a first type semiconductor layer, an active layer and a second type semiconductor layer. The metal reflective layer has a plurality of first concave sections, and a convex portion is formed within each first concave section. The first transparent electrically-conductive layer is conformally formed over the first concave sections and the convex portions of the metal reflective layer. The dielectric layer is formed over the first transparent electrically-conductive layer and has a plurality of second concave sections, each second concave section having a through hole to a portion of the first transparent electrically-conductive layer that is aligned with the convex portion. The second transparent electrically-conductive layers are formed within the second concave sections respectively, and connected with the first transparent electrically-conductive layer via the through hole. The first type semiconductor layer, an active layer and a second type semiconductor layer are serially formed over the dielectric layer and the second transparent electrically-conductive layers.

Another aspect of the present disclosure is to provide a light emitting diode structure, which includes a metal reflective layer, a first transparent electrically-conductive layer, a dielectric layer, a plurality of second transparent electrically-conductive layers, a first type semiconductor layer, an active layer and a second type semiconductor layer. The metal reflective layer has a plurality of first concave sections. The first transparent electrically-conductive layer is conformally formed over the first concave sections of the metal reflective layer. The dielectric layer is formed over the first transparent electrically-conductive layer and has a plurality of through holes to expose the first transparent electrically-conductive layer. The second transparent electrically-conductive layers are formed over the dielectric layer, and connected with the first transparent electrically-conductive layer via the through holes, wherein each second transparent electrically-conductive layer is connected to the first transparent electrically-conductive layer to form a T-shaped cross section in each first concave section. The first type semiconductor layer, an active layer and a second type semiconductor layer are serially formed over the dielectric layer and the second transparent electrically-conductive layers.

In one or more embodiments, each second transparent electrically-conductive layer has a grain size larger than that of the first transparent electrically-conductive layer.

In one or more embodiments, an area sum of all the second transparent electrically-conductive layers is smaller than one-third of a total area of the first transparent electrically-conductive layer.

In one or more embodiments, an area of each second concave section is smaller than an area of each first concave section.

In one or more embodiments, an area of each second transparent electrically-conductive layer is smaller than an area of each first concave section.

In one or more embodiments, an area of the through hole is smaller or equal to an area of each second transparent electrically-conductive layer.

In one or more embodiments, each second transparent electrically-conductive layer has a grain size that is 2 to 5 times larger than that of the first transparent electrically-conductive layer.

In one or more embodiments, a convex portion is formed within each first concave section, and the convex portion is aligned with a corresponding one of the through holes.

In one or more embodiments, a convex portion is formed within each first concave section, and the convex portion is connected to the T-shaped cross section.

In summary, the light emitting diode structure disclosed herein reduces an area of the relatively rough transparent electrically-conductive layer so that it can still perform its ohmic contact function, while covering a thicker dielectric layer to reduce its roughness. The other transparent electrically-conductive layer with a relatively smooth surface covers the dielectric layer, and is connected to the relatively rough transparent electrically-conductive layer via the through hole on the dielectric layer such that the subsequently formed metal reflective layer has a larger flat and smooth area in order to increase the light reflection efficiency and light extraction efficiency.

DETAILED DESCRIPTION

It is to be noted that the following descriptions of preferred embodiments of this disclosure are presented herein for purpose of illustration and description only. It is not intended to be exhaustive or to be limited to the precise form disclosed. Also, it is also important to point out that there may be other features, elements, steps and parameters for implementing the embodiments of the present disclosure which are not specifically illustrated. Thus, the specification and the drawings are to be regard as an illustrative sense rather than a restrictive sense. Various modifications and similar arrangements may be provided by the persons skilled in the art within the spirit and scope of the present disclosure. In addition, the illustrations may not necessarily be drawn to scale, and the identical elements of the embodiments are designated with the same reference numerals.

Reference is made toFIG. 1, which illustrates a cross sectional view of a light emitting diode structure in accordance with an embodiment of the present disclosure. The light emitting diode structure100includes a substrate102, a metal reflective layer106, a transparent electrically-conductive layer108, a dielectric layer110, a transparent electrically-conductive layer112, a semiconductor layer114, an active layer116, and a semiconductor layer118. In some embodiments of the present disclosure, the metal reflective layer106is made from materials that may include copper (Cu), aluminum (Al), indium (In), ruthenium (Ru), tin (Sn), gold (Au), platinum (Pt) , Zinc (Zn), silver (Ag), titanium (Ti), lead (Pb), nickel (Ni), chromium (Cr), magnesium (Mg), palladium (Pd) or any combinations thereof, but not being limited thereto. In some embodiments of the present disclosure, the metal reflective layer106has a plurality of concave sections106a,and each concave section106ahas a convex portion106b.In some embodiments of the present disclosure, the transparent electrically-conductive layer108is conformally formed over the concave sections106aand the convex portions106bof the metal reflective layer106. The materials of the transparent electrically-conductive layer108may include transparent conductive oxide (TCO) or thin metal layer. For example, the transparent conductive oxide may include indium oxide (In2O3), indium tin oxide (ITO), tin oxide (SnO2), Zinc oxide (ZnO), aluminum zinc oxide (AZO) or indium zinc oxide (IZO), but not being limited to this. The thin metal layer may include copper (Cu), aluminum (Al), indium (In), ruthenium (Ru), tin (Sn), gold (Au), platinum (Pt), zinc (Zn), silver (Ag), Titanium (Ti), lead (Pb), nickel (Ni), chromium (Cr), magnesium (Mg), palladium (Pd) or a combination thereof, but not being limited thereto.

In some embodiments of the present disclosure, the dielectric layer110is formed on the transparent electrically-conductive layer108and has a plurality of concave sections110a,and each concave section110ahas a through hole110bto expose the transparent electrically-conductive layer108and aligned with the raised portion108aover the convex portion106b.In some embodiments of the present disclosure, a plurality of transparent electrically-conductive layers112are located in these concave sections110arespectively, and are connected to the raised portion108aof the transparent electrically-conductive layer108via the through hole110b.

In some embodiments of the present disclosure, the semiconductor layer114, the active layer116, and the semiconductor layer118are sequentially formed on the dielectric layer110and these transparent electrically-conductive layers112. A portion of light beams emitted by the active layer116are directly output through an upper surface of the semiconductor layer118, and the other portion of light beams are reflected by the metal reflective layer106, and then output through the upper surface of the semiconductor layer118.

In some embodiments of the present disclosure, the transparent electrically-conductive layer108has a smaller (crystal) grain size (i.e., compared with the transparent electrically-conductive layer112) such that its surface is smoother. The metal reflective layer106that is in contact with the transparent electrically-conductive layer108also forms a smoother surface, which effectively reflects the light beams emitted by the active layer116, thereby enhancing a light-emitting efficiency of the light emitting diode structure.

In some embodiments of the present disclosure, the transparent electrically-conductive layer112has a larger (crystal) grain size and serves as an ohmic contact layer with the semiconductor layer114. Therefore, the transparent electrically-conductive layer112has a (crystal) grain size larger than that of the transparent electrically-conductive layer108.

In some embodiments of the present disclosure, an area sum of all the transparent electrically-conductive layers112is less or smaller than one-third of a total area of the transparent electrically-conductive layer108such that a negative effect of the transparent electrically-conductive layer112with a larger (crystal) grain size on light emission can be reduced, but not being limited thereto.

In some embodiments of the present disclosure, an area of each concave section110ais smaller than an area of a corresponding concave section106a,but not being limited thereto. In some embodiments of the present disclosure, an area of each transparent electrically-conductive layer112is smaller than an area of a corresponding concave section106a,but is not limited thereto.

In some embodiments of the present disclosure, a size, e.g., area, of the through hole110bis smaller than or equal to an area of each transparent electrically-conductive layer112. In some embodiments of the present disclosure, the (crystal) grain size of the transparent electrically-conductive layers112may be2to5times the (crystal) grain size of the transparent electrically-conductive layer108, but not being limited thereto.

In some embodiments of the present disclosure, each transparent electrically-conductive layer112is connected to the raised portion108aof the transparent electrically-conductive layer108to form a T-shaped cross section in each concave section106aof the metal reflective layer106. In some embodiments of the present disclosure, the convex portion106bin the concave section106ais connected to the T-shaped cross section.

Reference is made toFIGS. 2-9, which illustrate manufacturing steps of cross sectional views of a light emitting diode structure in accordance with various embodiments of the present disclosure. InFIG. 2, a semiconductor layer118, an active layer116, and a semiconductor layer114are sequentially formed on a native substrate122. In some embodiments of the present disclosure, the semiconductor layer118may be an N-type semiconductor layer, the active layer116may be a multiple-quantum well (MQW) layer, and the semiconductor layer114may be a P-type semiconductor layer.

InFIG. 3, a transparent conductive film is formed on a surface of the semiconductor layer114, and patterned into a plurality of transparent electrically-conductive layers112each of which serves as an ohmic contact layer with the semiconductor layer114. In some embodiments of the present disclosure, a shape (a top view shape) of each transparent electrically-conductive layer112may be a circle or an arbitrary polygon. In some embodiments of the present disclosure, a thickness of the transparent electrically-conductive layer112is at least 30 Angstroms or more, but not being limited thereto. The transparent electrically-conductive layer112has the characteristics of a larger (crystal) grain size and a large surface roughness, and serves as an ohmic contact layer with the semiconductor layer114.

InFIG. 4, the dielectric layer110is conformally formed over the semiconductor layer114and those transparent electrically-conductive layers112, thereby forming a plurality of concave sections110afor accommodating those transparent electrically-conductive layers112respectively, and a through hole110bis formed in each concave section110a.In some embodiments of the present disclosure, a thickness of the dielectric layer110is at least 400 Angstroms or more, but not being limited thereto. A thicker dielectric layer110over the larger surface roughness of the transparent electrically-conductive layer112forms a smoother surface for an opposite side of the dielectric layer110.

InFIG. 5, the transparent electrically-conductive layer108is conformally formed over a surface of the dielectric layer110to form a raised portion108a,and the raised portion108ais connected to the transparent electrically-conductive layer112via the through hole110b.In some embodiments of the present disclosure, a thickness of the transparent electrically-conductive layer108is at least 50 Angstroms or more, but not being limited thereto.

InFIG. 6, the metal reflective layer106is formed on the surface of the transparent electrically-conductive layer108, thereby forming a plurality of concave sections106aand convex portions106bof the metal reflective layer106, and each convex portion106bis located in each concave section106a.Because the transparent electrically-conductive layer108has a smaller (crystal) grain size and a smoother surface (compared with the transparent electrically-conductive layer112), the metal reflective layer106has a surface that is in contact with the transparent electrically-conductive layer108and has a flatter and smoother surface for reflecting light beams.

InFIG. 7, a conductive bonding layer104is used to bond a metal substrate102to the metal reflective layer106.

InFIG. 8, the structure completed inFIG. 7is turned upside down, and the native substrate122is removed.

InFIG. 9, a multi-metal electrode layer (120a,120b,120c) is formed on the semiconductor layer118, and a back metal layer102ais formed under the metal substrate102.

Referring toFIG. 1, a rough surface118ais finally formed on the surface of the semiconductor layer118to increase the light extraction efficiency, and the light emitting diode structure100is completed.

In summary, the light emitting diode structure disclosed herein reduces an area of the relatively rough transparent electrically-conductive layer so that it can still perform its ohmic contact function, while covering a thicker dielectric layer to reduce its roughness. The other transparent electrically-conductive layer with a relatively smooth surface covers the dielectric layer, and is connected to the relatively rough transparent electrically-conductive layer via the through hole on the dielectric layer such that the subsequently formed metal reflective layer has a larger flat and smooth area in order to increase the light reflection efficiency and light extraction efficiency.