Simulation of hydrogenated amorphous silicon: temperature dependence of nonequilibrium distribution functions for trap states

Abstract

The nonequilibrium distribution functions (NDF) for the trap states in the mobility-gap under photo illumination and zero bias voltage are derived by the constructed self-consistent drift-diffusion simulator consisted of the Poisson equation and current continuity equations for hydrogenated amorphous silicon (a-Si:H). As for the temperature dependence of the NDF, we find that the values of the NDF decrease with increasing temperature (the negative temperature dependence) in the energy region near the conduction band for p-type a-Si:H. That is the reverse of the temperature dependence of the equilibrium distribution functions (EDF) for the trap states in the mobility-gap. Furthermore, we show that the new physical characteristic is applicable to the explanation of the temperature characteristic of the photoconductivity caused by the electron hopping in the conduction band tail for a-Si:H. The photoconductivity of a-Si:H decreases with increasing temperature, which is called the thermal quenching (TQ).We show that the TQ observed in a low temperature around 200K for p-type a-Si:H can be explained by the electron hopping model with the p-type NDF having the negative temperature dependence.

Thin-film transistor arrays for biological sensing systems

“…Among them, a-Si:H TFT, LTPS TFT and metal oxide TFT has achieved a wide range of commercial applications, while the OTFT still remain in the laboratory stage [16]. The common fabrication process of a-Si:H TFT is plasma-enhanced chemical vapor deposition (PECVD); the a-Si:H TFT device has a well uniformity, but its carrier mobility is relatively lower [17,18]. The common fabrication process of OTFT is solution process or thermal evaporation; the OTFT device has the advantages of low cost and flexibility, but insufficient in the performance uniformity and device stability [19][20][21].…”