Electron transport of perovskite oxide BaSnO3 on (110) DyScO3 substrate with channel-recess for ferroelectric field effect transistors

Abstract

We report an electron transport study of an La-doped perovskite oxide BaSnO3 thin film grown by molecular beam epitaxy on (110) DyScO3 as a function of electron concentration, by etching the film step-by-step with nanometer precision. Inductively coupled plasma-reactive ion etching with BCl3/Ar plasma is used for etching depth control. The local doping and electron density are experimentally determined after each etching step. The results show that the electron mobility is dominated by threading dislocations if the electron concentration is below 7.8 × 1019 cm−3, while ionized impurities and phonon scattering become more dominant at electron concentrations greater than 1.2 × 1020 cm−3. The charging state of thread dislocations is estimated to be 6.2. Furthermore, using the etch process to control the electron concentration and channel thickness, a gate-recessed ferroelectric field effect transistor is fabricated with 10 nm HfO2 as a gate dielectric. The device exhibits a saturation current of 29.9 mA/mm with a current on/off ratio of Ion/Ioff = 8.3 × 108 and a ferroelectric polarization charge density of 1.9 × 1013 cm−2. Under the forward gate bias sweep, the device operates in the enhancement mode with a threshold voltage of 3 V. Under the reverse gate sweeping bias, the device operates in the depletion mode with a threshold voltage of –1.5 V.

High-Mobility Field-Effect Transistor Using 2-Dimensional Electron Gas at the LaScO3/BaSnO3 Interface

“…The field-effect mobility (μ FE ) was calculated via the relation where L , t , W , and ε 0 are the channel length, the thickness of the gate oxide, the channel width, and the permittivity of the vacuum, respectively. The maximum μ FE was calculated to be about 98.7 cm 2 V –1 s –1 , which is the highest value reported to date in FETs based on the Ba 1– x La x SnO 3 channel layer by using various gate oxides such as Al 2 O 3 , HfO 2 , ,− BaHfO 3 , and even LaInO 3 . ,, Although the transconductance ( g m ), defined as g m = ∂I DS / ∂V GS , is slightly higher in the previously reported FETs by using the LaInO 3 gate oxide than in the LaScO 3 gate oxide device, the relatively lower κ of the LaScO 3 gate oxide than that of LaInO 3 renders the FET to show greater μ FE . Taken together, such high performance of the device can be attributed to the high conductivity of the channel due to the formation of the 2DEG at the LaScO 3 /Ba 0.998 La 0.002 SnO 3 interface, as well as the gate dielectric properties of LaScO 3 , which is chemically stable at high temperatures with high κ, being one of the rare-earth scandates.…”

From Ferroelectric Material Optimization to Neuromorphic Devices

“…In three‐terminals devices, the weight update (Figure 6f) is performed using the gate (G) and the drain (D), whereas the reading (Figure 6g) is performed by the channel (S–D) read‐out. In this configuration, excellent I DS – V DS linearity was obtained using conducting oxides, for example $${\rm{W}}{{\rm{O}}_x}$$ [ 81 ] or BaSnO 3 [ 167 ] as channel materials. Indium–tin‐oxide (ITO) shows Ohmic conduction and can be combined with HZO in a BEOL compatible process.…”

Epitaxial BaSnO3 thin films with low dislocation density grown on lattice matched LaInO3 substrates

“…Epitaxial growth of BaSnO 3 thin films by PLD is performed for many years on various substrates, however its structural and electrical properties were always limited by the high density of threading dislocations (in the order of 10 11 cm −2 ) found in the grown films [25,[41][42][43], which are a consequence of a large lattice mismatch between substrate and film. The implementation of the novel lattice matched LaInO 3 substrates for the first time allowed the growth of BaSnO 3 thin films with high structural quality.…”