Atomic-layer-deposited LaAlO3/SrTiO3 all oxide field-effect transistors
We have demonstrated well-behaved accumulation-mode all oxide NMOSFETs with amorphous atomic-layer-deposited (ALD) LaAlO<inf>3</inf> gate dielectric stacks on crystalline SrTiO<inf>3</inf> substrates. A maximum drain current exceeding 10 mA/mm has been obtained on a 3.75µm-gate-length device, proving a very conductive channel can be formed at the oxide-oxide interface. Four different gate dielectric stacks, which are Lafirst cycle LaAlO<inf>3</inf>, Al-first cycle LaAlO<inf>3</inf>, LaAlO<inf>3</inf> with 1.5 nm La<inf>2</inf>O<inf>3</inf> interfacial layer, and LaAlO<inf>3</inf> with 1.8 nm Al<inf>2</inf>O<inf>3</inf> interfacial layer, have been deposited on SrTiO<inf>3</inf> substrates to systematically study their effects on the conductivity at the different oxide-oxide interfaces. The experimental results show that a La-initiated interfacial layer is preferable to form a more conducting channel at the LaAlO<inf>3</inf>/SrTiO<inf>3</inf> interface. Low temperature characteristics have also been utilized to provide an in-depth understanding of the channel formation at the oxide-oxide interface. The availability of the MBE technology to epitaxially grow SrTiO<inf>3</inf> on Si substrate provides the pathway to integrate ALD LaAlO<inf>3</inf>/SrTiO<inf>3</inf> devices on Si platform.