Preparation And Resonant Tunneling Characteristics Of Perovskite Double-barriers

Although electronic devices based on semiconductors are currently ubiquitous, the continuous miniaturization has been pushing these conventional devices to their physical limits. Oxides show a broad spectrum of electronic properties from insulating, semiconducting to metallic and have been considered to realize functionalities in next generation memory and logic devices. Among these, perovskites have long been known as hosts for a variety of useful electronic and magnetic characteristics. Their enormous chemical diversity and structural compatibility offer an opportunity to tailor electronic and magnetic properties in ways not possible with conventional semiconductors. The resonant tunneling diode (RTD) can be applied in analog and digital circuit, such as, microwave oscillators, logical gates, et al. Almost all the RTD devices to date are made of semiconductor double-barriers, mostly of III-V semiconductors. In this work, we tried to realize resonant tunneling through all-perovskite double-barriers and the modulation on negative resistance (NDR) by polarization reversal in a ferroelectric quantum well.We have prepared La-doped SrTiO3 (La:STO) targets using solid state reaction method, and optimized the epitaxial deposition of La:STO thin films on single-crystalline SrTiO3 (STO) substrates by pulsed laser deposition (PLD). La:STO/STO superlattices, La:STO/LaA103(LAO)/S TO/LAO and La:STO/LAO/BaTiO3(BTO)/LAO heterostructures have been deposited on the Nb-doped SrTiO3 (Nb:STO) substrates and their Ⅰ-Ⅴ characteristics have been measured. We have explored the modulation on the NDR by polarization reversal in the La:STO/LAO/BTO/LAO ferroelectric quantum well. The main conclusions are summarized below.1. The optimized deposition parameters of La:STO thin films on (001) STO substrates by PLD are 750 ℃ substrate temperature,0.001 mbar oxygen pressure,45 mJ laser energy,1.74 J/cm laser energy density, and 2 Hz laser repetition. X-ray diffraction and atomic force microscope analyses indicate that both La:STO thin films and all-perovskite heterstructures are of good epitaxial quality and smooth surface.2. Clear NDR due to resonance tunneling is achieved at room temperature in La:STO/LAO/STO/LAO/Nb:STO and La:STO/LAO/BTO/LAO/Nb:STO heterstructures.3. The modulation on the NRD by polarization reversal is realized in the La:STO /LAO/BTO/LAO/Nb:STO ferroelectric quantum well. The NRD voltage can be shifted by the polarization switching in BTO. Polarization pointing to Nb:STO lowers the NRD voltage, while polarization pointing to La:STO increases it. Such a shift is due to the change of the extra electrostatic energy added on quantized levels as the depolarization field in the quantum well is reversed.