A study of the ferroelectric field effect in Te films on lead germanate, triglycine sulphate, and triglycine selenate substrates

Abstract

Ferroelectric field effect was studied in three devices using lead germanate (Pb₅Ge₃O₁₁), triglycine sulphate (TGS), and triglycine selenate (TGSe) as ferroelectric substrates with tellurium (Te) semiconductor films at different temperatures between 90 K and the transition temperature of the ferroelectric substrates. The devices exhibit merit factors (ratio of ON and OFF conductivities) in the range of 10³-10⁵ at 0° C. However, the device performance seems to be governed by the traps at the ferroelectric-semiconductor interface and in the semiconductor film. The surface states and the density of charges responsible for conductivity modulation are evaluated by both Crawford's method and an integration method, and a reasonable agreement is observed in the numerical magnitudes. The activation energies obtained from the variation of drain-source conductance with temperature in both ON and OFF states are considerably higher than those measured for a Te film on a glass substrate. The merit factor showed a decrease both at low temperatures and near the transition temperatures. The decreases at high temperatures is consistent with the decrease in the polarization. The decreases in merit factor at low temperatures and the higher activation energy for conductance under field effect may be attributed to the trapping phenomenon.