form a structure such as illustrated in fig2 the illuminant epitaxial structure 202 comprises an n type semiconductor layer 202 a an active layer 202 b and a p type semiconductor layer 202 c in which a material of the n type semiconductor layer 202 a can be n type algainp or n type gan the p type semiconductor layer 202 c can be p type algainp or p type gan and the active layer 202 b can be a multiple quantum well structure for example after the illuminant epitaxial structure 202 is formed a transparent conductive layer 204 is formed to cover the illuminant epitaxial structure 202 so as to form a structure such as illustrated in fig3 in which a material of the transparent conductive layer 204 can be for example indium tin oxide ito zno cadmium tin oxide cto tiwn in 2 o 3 sno 2 mgo znga 2 o 4 sno 2 sb ga 2 o 3 sn agino 2 sn in 2 o 3 zn cualo 2 lacuos nio cugao 2 or srcu 2 o 2 the transparent conductive layer 204 is also called a transparent electrode layer and the transparent conductive layer 204 not only can have a good ohmic contact with the illuminant epitaxial structure 202 but also have a current spreading function next a thin reflective layer 206 is formed by evaporation sputtering electroplating or electroless electroplating and a material of the reflective layer 206 can be a reflective material such as au ag al in sn pt ti zn pb aube ni pbsn or auzn after the reflective layer 206 is formed a metal substrate 208 of large thickness is formed to form the structure illustrated in fig4 by evaporation sputtering electroplating or electroless electroplating the thickness of the metal substrate.