1. Field of the Invention
This invention relates to a light emitting element with a wide bandgap enough to emit visible light to ultraviolet light and a method of making the same, and relates particularly to a light emitting element employing a colorless, transparent and conductive substrate that transmits emit visible light to ultraviolet light, offering a vertical structure in electrode configuration, and allowing emitted light to be outputted from the substrate side and a method of making the same.
2. Description of the Related Art
Conventionally, a light emitting element with a composition of SiC substrate/n-GaN/p-GaN is known (e.g., Japanese patent application laid-open No. 2002-255692).
SiC is brown and transparent material, and it transmits visible light up to about 427 nm. Therefore, a light emitting element employing the SiC substrate allows emitted light to be outputted from the substrate side.
The light emitting element employing a SiC substrate is manufactured by epitaxially growing SiC thin film on a SiC single crystal wafer to get the SiC substrate, then growing n-GaN and p-GaN layers on the substrate, cutting out light emitting element chips.
However, there is a serious problem in the light emitting element employing the SiC substrate. The SiC single crystal wafer has a bad crystalline quality such that there exist micro-pipe defects penetrating vertically in the SiC single crystal wafer. Therefore, it is required that, when making chips from a wafer having n-GaN and p-GaN layers grown thereon, the wafer must be carefully cut while avoiding the micro-pipe defect. This causes a bad efficiency in the manufacture of light emitting element.
On the other hand, SiC transmits up to light of blue region but does not transmit light of ultraviolet region. When GaN-emitted light including visible light to ultraviolet light is outputted from the substrate side, the light of ultraviolet region cannot be transmitted therethrough. Thus, ultraviolet light cannot be outputted from the substrate side. Furthermore, SiC is brown-colored and, therefore, when transmitting light through SiC, part of emitted light wavelength must be absorbed.