High-power laser structures grown on bulk GaN crystals

Abstract

High-pressure-grown bulk GaN crystals have the best reported structural quality and the lowest defect density among all available GaN substrates. We report on MOVPE growth, device processing and properties of high-power laser structures on such substrates. In this work, we describe very high optical output power per laser facet of 1.9 W from single LD device with 15 μm×500 μm cavity. The measured value is up to our knowledge the highest nitride laser power reported. Also, the electrical and optical power densities, yet pulsed, are in the range of the highest reported for broad area lasers what confirms that nitride-based wide bandgap structures are capable of handling very high power. From thermally accelerated electrical ageing tests we extracted the activation energy of one of degradation mechanisms to be 0.32 eV. Catastrophic optical damage was not observed up to power density of 40 MW/cm 2. Demonstrated results show that the availability of very low defect density GaN substrates is clearly the key issue in fabrication of highly reliable devices and high power LDs.