Density Of Acceptor-like States Research Articles

Single-Scan Monochromatic Photonic Capacitance-Voltage Technique for Extraction of Subgap DOS Over the Bandgap in Amorphous Semiconductor TFTs

We report a novel technique for simultaneous extraction of subgap donor- and acceptor-like density of states [gD(E) and gA(E)] over the subgap energy range (EV <;E<;EC) using a single-scan monochromatic photonic capacitance-voltage technique in n-channel amorphous indium-gallium-zinc-oxide thin-film transistors. In the proposed technique, we applied two different equivalent circuit models for the photoresponsive carriers excited from gD(E) and gA(E) under depletion (VGS <; VFB) and accumulation (VGS <; VFB) bias by employing a sub-bandgap optical source that includes a relation between photon energy (Eph) and bandgap energy (Eg) as hv = Eph <; Eg.

Investigation on mechanism for instability under drain current stress in amorphous Si–In–Zn–O thin-film transistors

The mechanism for instability against positive bias stress (PBS) in amorphous Si–In–Zn–O (SIZO) thin-film transistors has been investigated by analyzing the subgap density of states (DOSs), which was extracted from multi-frequency method using direct capacitance–voltage measurements. It was found that DOSs including shallow tail states and deep trap states are constant in density as PBS time increases. It indicates that the bulk traps in the SIZO channel layer and the channel/dielectric interfacial traps are not created during the PBS duration. Therefore, the instability against PBS in SIZO thin-film transistors is attributed to the charge trapping by the acceptor-like DOSs.

Modeling of amorphous InGaZnO thin-film transistors based on the density of states extracted from the optical response of capacitance-voltage characteristics

In order to model dc characteristics of n-channel amorphous InGaZnO thin-film transistors from experimentally obtained density of states (DOS), the acceptorlike DOS is extracted from the optical response of capacitance-voltage characteristics and confirmed by the technology computer-aided design (TCAD) simulation comparing with the measured data. Extracted DOS is a linear superposition of two exponential functions (tail and deep states), and its incorporation into TCAD model reproduces well the experimental current-voltage characteristics over the wide range of the gate and drain voltages. The discrepancy at higher gate voltage is expected to be improved by incorporating a gate voltage-dependent mobility in the model.