Lateral electrical transport and photocurrent in single and multilayers of two-dimensional arrays of Si nanocrystals

Abstract

We have investigated electrical transport and photocurrent in single and multilayers of two-dimensional arrays of silicon nanocrystals (SiNCs) suitable for photovoltaic applications. The films were grown on quartz by low pressure chemical vapor deposition of Si and subsequent thermal oxidation steps. We found that at high voltages, electrical transport is governed by space charge limited currents due to the presence of traps. At low voltages, electrical transport is ohmic. Carrier mobility, carrier concentration, and trap density in the films were extracted from the electrical measurements. Combining photocurrent and absorption measurements for the films with different SiNC sizes, we found a remarkable similarity in the photon energy dependence of the photocurrent and of the absorbed light from the SiNCs, confirming a proportionality relation between the two quantities. Also, from the combined study of electrical transport and photocurrent, minority carrier lifetimes were extracted.