SELF-ORGANIZED InGaN/GaN MULTIPLE QUANTUM WELL NANOCOLUMN LIGHT EMITTING DIODES GROWN ON (111) Si SUBSTRATE

摘要

High optical quality GaN nanocolumns and InGaN/GaN multiple quantum well (MQW) nanocolumn LEDs were grown on n-type (111) Si substrates by rf-plasma assisted molecular beam epitaxy. Low and high excitation photoluminescence (PL) measurements were carried out to evaluate the optical quality of undoped GaN nanocolumns. The spontaneous emission intensity was 12 times stronger than that of GaN films grown by metalorganic chemical vapor deposition (MOCVD) with a dislocation density of 3～5 x l0~9 cm~(-2) and the threshold power density of stimulated emission was 290 kW/cm~2. These PL characteristics were comparable to that of the GaN nanocolumns grown on (0001) Al_2O_3 substrates. Nanocolumn LEDs were fabricated by forming Ni/Au transparent electrodes on the as-grown surface of p-n junction nanocolumns with an InGaN/GaN MQW active layer. The diodes showed clear rectifying behavior with a typical turn-on voltage of 2.5～3.0 V. A yellowish orange emission was observed through the transparent electrode under continuous-wave current operation at room temperature.