Extraction Technique for Intrinsic Subgap DOS in a-IGZO TFTs by De-Embedding the Parasitic Capacitance Through the Photonic $C$– $V$ Measurement

Abstract

We report a technique for extraction of the intrinsic subgap density of states (gA,int(E)) by deembedding the parasitic capacitance in amorphous indium-gallium-zinc-oxide TFTs through the optical charge pumping method. As structure-dependent parameters in the proposed extraction technique, the overlap length LOV between the source/drain (S/D) and the active layer and the parasitic overlap area between the gate and the S/D metal (Cpar,S/Cpar,D) are considered under dark and subbandgap photonic states. We obtained gA,int(E) as a superposition of the exponential deep and tail states with NTA,int = 6.0 × 1016 eV-1·cm-3, kTTA,int = 0.16 eV,NDA,int = 1.8 × 1015 eV-1 · cm-3, and kTDA,int = 1.9 eV from samples with various parasitic areas.