Self-Consistent Technique for Extracting Density of States in Amorphous InGaZnO Thin Film Transistors.

The self-consistent technique for extracting density of states [DOS: g(E)] in an amorphous indium gallium zinc oxide (a-IGZO) thin film transistor is proposed and demonstrated. The key parameters are the g(E) of the a-IGZO active layer and the intrinsic channel mobility (μ_ch). While the energy level (E) is scanned by the photon energy and gate-to-source voltage (V_GS) sweep, its density is extracted from an optical response of capacitance-voltage characteristics. Using the Vos-dependent μ_ch as another boundary condition, a linearly mapped DOS assuming a linear relation between V_GS and E is translated into a final DOS by fully considering a nonlinear relation between V_GS and E. The final DOS is finally extracted and verified by finding the self-consistent solution satisfying both the linearly mapped DOS and the measured V_GS dependence of μ_ch with the numerical iteration of a DOS-based μ_ch model. The extracted final DOS parameters are NTA = 1.73 x 10¹⁷ cm^-3 eV^-1, NDA = 3.5 x 10¹⁵ cm^-3 eV^-1, kT_TA = 0.023 eV, kT_DGA = 1.2 eV, and E_O = 1.7 eV with the formula of exponential tail states and Gaussian deep states. [ABSTRACT FROM AUTHOR]