Investigation of GaN on Si(111) for optoelectronic applications

GaN-based optoelectronics allow covering the spectral range from green to UV. Silicon (Si) is an alternative substrate to the commonly used sapphire and silicon carbide (SiC) but requires sophisticated buffer structures. In this work, two high-temperature (HT) layer stacks and two low-temperature (LT) AlN layers were used for the growth of GaN buffers for optoelectronic devices on (111)-oriented Si substrates using AIXTRON metalorganic vapor phase epitaxy (MOVPE) reactors. AlN, AlGaN and GaN were grown as HT layer stack to form stress reduction layers. GaInN MQW (multi quantum wells), electroluminescence test structures (ELT) and AIN/GaN DBR (distributed Bragg reflectors) were deposited on these buffer structures on Si. The growth process was monitored by in-situ reflectivity measurements. Photoluminescence (PL), electroluminescence and the luminescence under high optical excitation of the samples on Si have been studied. Laser action at optical excitation was obtained in the MQW with a room temperature (RT) laser threshold of I_thr = 40 - 80 kW/cm ². Laser action was achieved up to 350 °C. Electroluminescence emission from the ELT InGaN/GaN heterostructures was observed and measured under a minimal DC voltage of about 4 V. AlN/GaN DBR with ten periods showed reflectivities of 60% for wavelengths of 436 nm and 537 nm, respective.