Fabrication and characteristics of blue LED on GaN/Si (111) epitaxy grown with Al _0.3Ga _0.7N/GaN superlattice interlayer

In this study, we examine the growth of an Al _0.3Ga _0.7N/GaN superlattice as an intermediate layer between a n-GaN layer and A1N buffer layer, in order to control the tensile stress induced by cooling after growth. The purpose of this superlattice is to avoid the abrupt change in the thermal expansion coefficient between the GaN layer and Si substrate and to improve the structural and optical properties of the n-GaN layer. Next, we report on the fabrication and characterization of blue InGaN/GaN multiple-quantum well (MQW) light-emitting diodes (LEDs) on the GaN/Si(111) epitaxy-grown with this Al0.3Ga0.7N/GaN superlattice interlayer by metalorganic chemical vapor deposition (MOCVD). The turn-on voltage of the top-side contact of the LED is 4.1 V, and the operating voltage is 5.3 V at 20 mA. This LED had a fullwidth at half maximum (FWHM) of 40 nm for the electroluminescence (EL) peak shown at 488 nm and an optical output power of 6.7 μW under an applied current of 20 mA. It was found that the performance of the LED on GaN/Si(111) was poor compared with that on GaN/sapphire, which was the result of defects such as cracks and dislocations. In particular, we consider that the cracks are the main impediment to the growth of high quality LEDs on Si(111), as they act as current scattering centers for light propagation.