Double Gate PbS Quantum Dot Field-Effect Transistors for Tuneable Electrical Characteristics

In this work colloidal quantum dots double gate transistors are introduced. A high-k (k = 43) relaxor ferroelectric polymer is used as a dielectric material for the top gate in a device where the other gate is fabricated from SiO₂. The device in double gate configuration is characterized by reduced hysteresis in the transfer curves measured by separately sweeping the voltage of the SiO₂ and of the polymer gate. Gating with the relaxor polymer leads to mobility values of μ_e = 1.1 cm² V⁻¹s⁻¹ and μ_h = 6 × 10⁻³ cm² V⁻¹s⁻¹ that exceed those extracted from the SiO₂ gating: μ_e = 0.5 cm² V⁻¹s⁻¹ and μ_h = 2 × 10⁻³ cm² V⁻¹s⁻¹. Measurements under double gating conditions prove that the device works in a single channel mode that is delocalized over the whole film thickness. Double gating allows for shifting the threshold voltage into a desired position and also allows increasing the on-current of the devices.