A method for fabricating GaN-based LED is provided. The substrate, which is made of a dielectric material or a magnetic material, has a first surface. Stabilizing agents may be any biodegradable material such as starches, modified starches, cellulose, dextran, polymers, proteins, and collagen. As a result, even in the case of directly overwriting data recorded in either of the L0 layer 20 or the L1 layer 30, a sufficiently high erasing efficiency can be ensured.