Silicon carbide blue light emitting diodes with improved external quantum efficiency

Abstract

The most relevant features in the fabrication and room temperature operation of blue light emitting 6H-SiC:Al,N diodes are reported. Epilayers are grown either on opaque Acheson substrates or on semi- to fully transparent substrate platelets obtained from larger ingots grown in our laboratory. The p-n junction is obtained by overcompensating Al acceptors with N donors. Electroluminescent light, which is mainly due to N-donor-Al-acceptor pair recombination is generated in the n region of the diode. The emission spectrum is saturated to about 90% at normal driving conditions, the hue of the diodes being slightly dependent on the current density. Optimization of diode preparation and design, especially the use of transparent substrates, yields external quantum efficiencies of 1.1×10−4 for unencapsulated samples, nearly triplicating the best quantum efficiency values for SiC:Al,N diodes reported so far.