Optical properties of GaN grown on porous silicon substrate

Abstract

A photoluminescence (PL) study of GaN grown on Si(100) substrate using porous silicon (PS) as an intermediate layer is reported. The samples were characterized using PL for the temperature range 5-300 K under various excitation powers from 5 to 50 mW. For growth temperatures below 800°C, the room temperature PL shows a broad peak located around cubic GaN emission. This is in clear contradiction with previous scanning electron microscopy and X-ray measurements. At low PL temperature, the observed lines located at 3.306 and 3.364 eV have a narrow full width at half maximum of about 6 and 10 meV, respectively. When the excitation power was varied, no peak shift was observed. These peaks were assigned as deeply localized excitons related to stacking faults near the PS/GaN interface. Quantum confinement (type I or II) due to the presence of nanometric cubic inclusions is another possible explanation for the low-temperature PL. © 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.