A contactless method to study carrier kinetics in SnS thin films

Contactless methods to study laser-induced carrier kinetics present important advantages for materials characterization without necessity for contact fabrication. For example, mobility and lifetime of photogenerated carriers are studied by the transient grating method and by the transient photoluminescence technique. In this report we will mainly discuss the Microwave Transient Reflection (MWTR) technique in the nanosecond time regime applied to thin films of undoped and Ga-doped tin sulphide, SnS. As described in detail in previous publications, the SnS thin films were produced by Chemical Bath Deposition (CBD) from appropriate precursor solutions, and characterized with respect to morphological, structural, and optoelectronic properties by optical transmission, SEM and AFM, XRD, XPS, and RBS. We also add a detailed analysis of the optical properties from Spectral Ellipsometry (SE). The kinetics of photoinduced carriers after high-power laser pulses was monitored for a series of SnS samples after different anneal procedures with temperatures up to 600 °C. Overall power law decays observed in the MWTR signals is discussed in relation to trap state distributions by applying a simple recombination and reemission model. The results are compared to conventional time-resolved photocurrent measurements, TPC, which show similar power law decays.