Photoluminescence imaging under applied bias for characterization of Si surface passivation layers

• Published in: Solar energy materials and solar cells 2012-11, Vol.106, p.60-65
• Main Authors: Haug, Halvard, Nordseth, Ørnulf, Monakhov, Edouard V., Marstein, Erik Stensrud
• Format: Article
• Language: English
• Subjects: Applied sciences; Bias; Depletion; Electrical engineering. Electrical power engineering; Exact sciences and technology; Field-effect; Illumination; Imaging; Insulators; Inversions; Passivation; Photoluminescence; Silicon; Silicon nitride; Various equipment and components
• ISSN: 0927-0248; 1879-3398
• DOI: 10.1016/j.solmat.2012.05.041

In this work, we present a novel characterization technique for the analysis of Si surface passivation layers, using a photoluminescence imaging setup. In this technique the effective lifetime of passivated Si wafers is measured while applying an external bias over a rear side dielectric film. We demonstrate that this method can be used to analyze the passivation of silicon surfaces in inversion, depletion and accumulation conditions. In this paper the method is illustrated by characterization of a-SiNx:H passivation layers deposited by plasma enhanced chemical vapor deposition. The characterization results are interpreted both in the framework of the extended Shockley–Read–Hall theory and by PC1D simulations. For the a-SiNx:H layers, the effective surface recombination velocity parameter is found to be 5 to 7 times larger for electrons than for holes and the fixed insulator charge density is found to be 6.1−6.5×1011cm−2 under illumination, in agreement with results from capacitance–voltage measurements. ► A novel characterization technique for analyzing Si passivation layers is presented. ► Lifetime is measured by PL imaging while applying voltage to a gate electrode. ► Measurements are presented for PECVD a-SiNx:H layers. ► Results are compared to a one-dimensional SRH model. ► Simulation parameters are in agreement with complementary C–V measurements.