Laser direct writing and doping has already been successfully demonstrated for fabrication of PIN diodes, Ohmic and Schottky contacts and other optical structures in silicon carbide (SiC). Although SiC is an indirect bandgap semiconductor a SiC green light emitting diode (LED) has been recently shown to perform better than a GaN green LED. This observation is primarily due to 1) a simple device structure in SiC as opposed to the multilayered structure in GaN and other high bandgap semiconductor compounds and 2) high thermal conductivity. This initial phase focuses on the fabrication of reference SiC LED's to baseline this novel laser direct writing and doping process.

6H:SiC (n-type) wafer samples were used for fabrication of LED's. A Nd:YAG laser (1064nm wavelength) was used in continuous wave mode as well as pulsed mode for doping. Doping process iterations were carried out to obtain a uniform doped layer. Two different techniques were employed for patterning: 1) top doping where the incident laser beam assists in doping on the top surface and 2) bottom doping where the bottom surface is doped using the same top incident laser beam. Different structures were synthesized using these two doping techniques. P-type dopants such as boron (in powder form) and aluminum (metalorganic compound tri-methyl aluminum) and n-type dopant (pure nitrogen gas) were used. The doped structures were characterized for I-V characteristics, C-V characteristics and electroluminescence.

Electroluminescence (EL) spectrum of the doped samples showed the output in the range of blue to blue green for different samples and the different doped structures. The feasibility of wavelength tuning using nanostructure patterning has also been explored.