Influence of MOVPE growth temperature on the structural and optical properties of InGaN MQW laser diodes

The morphological and optical properties of InGaN multiple quantum wells (MQWs) emitting at 405 nm are studied with respect to the MQW growth temperature. The latter was varied between 760 and 840 °C in structures grown on c-plane sapphire substrates by metal-organic vapor-phase epitaxy (MOVPE). The indium content in the quantum well was kept constant for all temperatures by adjusting the trimethylindium supply. The MQWs were inserted as active region in both optically pumped laser heterostructures and laser diodes (LDs). We found that low growth temperatures result in a reduced spatial uniformity of the luminescence emission wavelength due to well thickness variations, whereas at higher temperatures it is difficult to obtain a spatially homogeneous indium concentration. A minimum threshold power density for optically pumped lasing was found for growth temperatures of the active region between 780 and 820 °C. LDs with an MQW grown at these conditions showed an onset of lasing at a current density of 6.5 kA/cm2 with output powers of more than 350 mW.