Proof-of-Concept Framework to Separate Recombination Processes in Thin Silicon Wafers using Transient Free-Carrier Absorption Spectroscopy

We present a proof-of-concept framework to independently determine the bulk Shockley-Read-Hall (SRH) lifetime and surface recombination velocity in silicon wafers self-consistently. We measure the transient decay of free-carrier absorption (FCA) using two different excitation wavelengths (1050 and 750 nm) for p-type crystalline Si (c-Si) wafers over a wide injection range and fit the FCA transients for the two excitation wavelengths in a coupled manner. In this way, we can estimate the surface recombination lifetime accurately. However, we find that the capability to uniquely measure extrinsic bulk-SRH recombination is challenging in the presence of other recombination processes and can be broadly categorized into five different regimes depending on the relative strengths of each recombination pathway.