Excitation power dependent photolu‐ minescence of PECVD a‐SiO_x:H (x<2) thin films

Abstract

The excitation power dependent visible photoluminescence (PL) property of an a‐SiOx:H (x &lt; 2) sample prepared in a PECVD system is studied within a temperature range of 12 K and 400 K. An explicit PL band was observed at the photon energy of 2.1 eV. It was observed that the PL intensity increased with a power of the excitation intensity (IPL∝Lγ) changed between 1.3 mWcm‐2 and 25 mWcm‐2. γ was calculated to change between 0.8‐1.2 depending on the measurement temperature. The 2.1 eV PL band was found to show weak thermal activation energy around room temperature and calculated as about 1meV. The temperature dependence of PL for each excitation power was fitted to a function proposed due to the thermal activated radiative recombination and the defect related non‐radiative recombination mechanism. As a result of the model the ratio of the average distance between a carrier and the non‐radiative defect center to the decay length of the wave function of the defect was calculated to be varying between 21 and 33 with increased generation rate range of 1.75x1016 cm‐3/s‐3.5x1017 cm‐3/s. The results were discussed in terms of the separation of phases and the behavior of thermally activated incoherent hopping migration of electrons to combine with self trapped holes (STH) to form self trapped excitons (STE). (© 2010 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)