A Light-Emitting Diode device is a well-known solid state lighting element, which emits light once if a voltage is applied thereto. The Light-Emitting Diode device generally includes a diode region (which is usually called as an epitaxial layer) which includes an N-type layer, a P-type layer and a P-N junction, where an anode contact is in ohmic contact with the P-type layer and a cathode contact is in ohmic contact with the N-type layer. Typically, the diode region, i.e. the epitaxial layer, may be formed epitaxially on a substrate and the epitaxial layer is generally made of gallium nitride-based material. Moreover, a sapphire is typically chosen as a substrate for growth of the epitaxial layer due to the restriction by a crystal structure and growth conditions of gallium nitride.
However, there exist the following problems in the technical solutions of the prior art. Due to the poor thermal conductivity and electrical conductivity of the sapphire, the Light-Emitting Diode device made of the gallium nitride-based material has a poor heat dissipation property, a short lifespan and a complicated manufacturing process, thus limiting the application of the sapphire in high power (i.e., high brightness) Light-Emitting Diodes. Furthermore, for a gallium nitride-based Light-Emitting Diode (GaN-based LED) device having a structure with a horizontal formal electrode, a P-type electrode will block light, thus the P-type electrode is required to have a good ITO extension layer, resulting in a low light efficiency and a complicated manufacturing process of the GaN-based LED device.
In order to solve the above problems, one of the existing improved solutions adopts silicon carbide (SiC) as a substrate and utilizes a structure with electrodes one above the other. However, although the improved solution effectively solves the above problems of heat dissipation and light blocking, silicon carbide is difficult to process and is even more costly than the sapphire, thereby restricting the application and promotion of the improved solution.
Further, another one of the existing improved solutions adopts a combination of a bonding technology and a peel-off technology, thus the epitaxial layer of the gallium nitride-based Light-Emitting Diode device is transferred to other substrate with high electrical conductivity and high thermal conductivity (which is for example made of an alloy material based on silicon (Si), copper (Cu) and aluminum (Al)). This improved solution eliminates the adverse effects of the sapphire substrate on the gallium nitride-base Light-Emitting Diode device. However, since a bonding substrate has a low light reflectivity, a reflective metallic layer must be deposited beyond an ITO extension layer of an LED chip in order to improve the light extraction efficiency. However, due to the use of the reflective metallic layer and the bonding technology, the another one of the existing improved solutions is defective in that: process difficulty and costs are increased, a chip of a structure with formal electrodes cannot be used for manufacturing the Light-Emitting Diode device, an electrode in the light emitting surface blocks light to be emitted so that the light extraction efficiency is reduced, and the wiring for the LED chip is difficult.
Therefore, there exists a need to provide a Light-Emitting Diode device (especially a high power Light-Emitting Diode device) with an improved light efficiency and an improved electrode structure and a manufacturing method thereof.