1. Field of the Invention
The present invention relates to a vertical light emitting diode (LED) and a method of manufacturing the same, which can reduce contact resistance of an negative electrode formed on the surface of an n-type GaN layer and can enhance thermal stability.
2. Description of the Related Art
Generally, a nitride-based semiconductor LED is grown on a sapphire substrate, but the sapphire substrate is a rigid nonconductor and has poor thermal conductivity. Therefore, there is a limitation in reducing the manufacturing costs by reducing the size of a nitride-based semiconductor LED, or improving the optical power and chip characteristic. Particularly, because the application of a high current is essential for achieving high power LED, it is important to solve a heat-sink problem of the LED. To solve this problem, there has been proposed a vertical LED in which a sapphire substrate is removed using Laser Lift-Off (LLO).
Hereinafter, a conventional vertical LED will be described in detail with reference to FIG. 1. FIG. 1 is a cross-sectional view of a conventional vertical LED.
As shown in FIG. 1, the conventional vertical LED has a structure support layer 150 formed in the lowermost portion and a positive (p-) electrode 140 formed on the structure support layer 150. Preferably, the p-electrode 140 is formed of a conductive reflecting member serving as an electrode and a reflecting layer.
On the p-electrode 140, a p-type GaN layer 130, an active layer 120, and an n-type GaN layer 110 are sequentially formed, thereby forming a light emission structure.
An upper portion of the light emission structure, that is, the surface of the n-type GaN layer 110 has surface irregularities (not shown) for enhancing light emission efficiency. On the n-type GaN layer 110, a negative (n-) electrode 160 is formed.
In the conventional vertical LED, however, the surface of the n-type GaN layer 110 coming in contact with the n-electrode 160 is an N-face or N-polar surface which comes in contact with a sapphire substrate (not shown) on which the n-type GaN layer is formed.
When the n-electrode 160 is positioned on the n-type GaN layer 110 having an N-face or N-polar surface, the contact resistance of the n-electrode increases, and thus an operational voltage of the LED increases. As a result, a heating value increases.
As such, when a heating value increases so that the thermal stability of the vertical LED decreases, the contact resistance of the LED also continuously increases, thereby degrading characteristics and reliability of the vertical LED.