Stimulated emission from GaN nanocolumns

Stimulated emission with very low threshold excitation power density was observed for GaN nanocolumns grown on (0001) sapphire substrate by RF‐plasma assisted molecular beam epitaxy. The photopump measurements were carried out under 355 nm Nd:YAG laser excitation with the surface emission configuration. The threshold excitation power density was 198 kW/cm2 at room temperature. The peak wavelength shifted from 370.2 to 370.9 nm when increasing the excitation power from 130 to 440 kW/cm2. The peak intensity increased nonlinearly with excitation power. For the lower excitation condition using a 325 nm He–Cd laser, the spontaneous emission peak was observed at 363.2 nm and the intensity was 20∼30 times stronger than for a 3.7 μm‐thick MOCVD‐grown GaN film with a dislocation density of 3∼5 × 109 cm–2. With this configuration the peak intensity was increased propotionally with excitation power. These results indicate that GaN nanocolumns have high potential to realize high performance optical devices. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)