Ferroelectric polymer gate on AlGaN∕GaN heterostructures

Abstract

There has been much investigation into the implementation of field effect transistors; however, a commercial device is still not available. An attempt is made here to develop a ferroelectric gate device using an Al0.3Ga0.7N∕GaN heterostructure with a two dimensional electron gas (2DEG). The ferroelectric copolymer poly(vinylidene fluoride∕trifluoroethylene) [P(VDF∕TrFE)] was chosen as a gate material due to advantages such as its small dielectric constant and low crystallization temperature in comparison with the perovskite ferroelectrics. A P(VDF∕TrFE) layer was successfully deposited onto an Al0.3Ga0.7N∕GaN heterostructure without degrading the transport properties of the 2DEG. The polarization reversal in the gate was proved by piezoelectric scanning force microscopy. With this structure, it was possible to demonstrate the ferroelectric gate operation when modulating the transport properties of the 2DEG due to the stable reversal of the spontaneous polarization in the gate. Transport measurements in combination with piezoelectric scanning probe microscopy enable an insight into the physical origin of the retention loss in the system.