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Device dimension scaling down to be comparable to the domain size of polycrystalline ferroelectric HfZrO2 (HZO) is evaluated for subthreshold swing (SS) and drain-induced barrier lowering (DIBL) by numerical simulation. The proposed multi-domain modeling involves polarization random location in HZO and probability with Gaussian distribution, as well as being integrated with the Landau–Khalatnikov equation. A small device with a few domains exhibits steep SS compared with large dimension with many domains. The N-DIBL (negative-DIBL) is also estimated by using this model, and the negative capacitance effect retards the short-channel effects significantly. The trend of the experimental data and simulation results of fin field-effect transistors and planar field-effect transistors is consistent with nano-scale and micro-scale devices, respectively. [ABSTRACT FROM AUTHOR]

Atomic layer deposition (ALD)-based TiN electrode on ferroelectric HfZrO2 metal/ferroelectric/metal (MFM) capacitor and ferroelectric field-effect transistor (FeFET) is demonstrated experimentally with weight transfer, that is, ΔP, per pulse analysis through consecutive alternating potentiation/depression (Pot./Dep.) training pulses. The weight training pulse schemes are studied to have symmetric and linear synapse weight transfer to increase the accuracy and accelerate the deep neural network (DNN) training. With ALD TiN inserted, αp/αd = −0.63/−0.84, asymmetry |αp−αd| = 0.21, and polarization modulation ratio (Pot./Dep.) = 97%/98% are achieved for MFM capacitor, and αp−αd = −1.32/−1.88, asymmetry |αp−αd| = 0.56, and Gmax/Gmin > 10 × are delivered for FeFET. [ABSTRACT FROM AUTHOR]

Raman shifts are investigated on silicon and germanium substrates under the uniaxial tensile strain on various substrate orientations. The strain splits the triply degenerate optical (LO, TO) phonons at the zone center (kvector ≈0). The redshifts of Si Raman peaks induced by the tensile strain on all substrate orientations are observed. With the specific polarization of the incident light, however, the unusual blueshifts of Ge Raman peaks induced by the tensile strain are observed on (110) and (111) Ge substrates. By using the suitable phenomenological constants and taking the Raman selection rules into consideration, the experimental results are in reasonable agreement with the lattice dynamical theory. [ABSTRACT FROM AUTHOR]

The directional, density-of-states, and carrier-concentration effective masses of light, heavy, and split-off holes have been calculated for strained Si1-xCx alloys on Si (001) substrate. The results for the directional effective mass show that the effect of strain makes the constant energy surface of light holes near the band edge more symmetric than that in pure silicon. The effect of strain on the heavy and split-off hole bands is rather regular; up to 7% of carbon concentration the strain effect monotonically reduces the density-of-states effective mass for the two bands at energy values within energy interval of 0.4 eV below the valence band edge. This reduction is obtained for the carrier-concentration effective mass at temperatures from 0 to 600 K. The strain effect on the light hole band is less trivial; at nonzero carbon concentrations the strain effect influences the density-of-states and the carrier-concentration effective mass in a similar way as it does to the heavy and split-off bands but irregular behavior shows up in the energy interval of 0.02 eV below the valence band edge and at the temperature range from 0 to 140 K. At 7% of carbon doping the total density-of-states effective mass for holes at 77 and 300 K are almost the same, namely, the values are 0.39 and 0.40 in units of free electron mass, respectively. [ABSTRACT FROM AUTHOR]

We report the energy band structures of strained Si[sub 1-x]C[sub x] alloys on Si (001) substrates. All calculations are based on a 20×20 Hamiltonian matrix constructed from the linear combination of atomic orbital approximation with spin-orbit interaction, strain effect, and lattice disorder effect taken into account. The lattice disorder parameter is obtained from fittings with the experimental band gap of strained Si[sub 1-x]C[sub x] alloy with small carbon concentration and reflects the initial reduction of band gap of relaxed Si[sub 1-x]C[sub x] alloy, while simple virtual crystal approximation does not. The effect of strain on band structure is incorporated in terms of the interatomic interaction parameters, which are functions of bond length and bond angle. The strained Si[sub 1-x]C[sub x] alloy becomes metallic when x = 28%. All the directional effective masses are affected by the strain. Overall agreements are found between our theoretical calculations and recent experimental results. [ABSTRACT FROM AUTHOR]

Characteristics of electroluminescence from indium tin oxide (ITO)/SiO[sub 2]/Si metal-oxide-semiconductor (MOS) structures fabricated on both p-type and n-type Si wafers were investigated. The ITO/SiO[sub 2]/Si MOS on p-type Si could have both the visible and band edge electroluminescence, while the ITO/SiO[sub 2]/Si MOS on n-type Si has only band edge emission. The reason for the difference is attributed to the impact ionization that only occurs for ITO/SiO[sub 2]/Si(p) MOS. The study indicates that the band edge emission and visible luminescence are competing processes. The electroluminescence from ITO/SiO[sub 2]/Si(n) is also discovered to be less than that from the Al/SiO[sub 2]/Si(n). The reason is possibly due to the damage of the oxide bonding and the SiO[sub 2]/Si interface during the ITO sputtering. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

FeFETs with 5-nm-thick Hf0.5Zr0.5O2 (HZO) have been demonstrated in memory operations for the ON/OFF current ratio >104 at zero gate voltage and a memory window (MW) of 0.6–0.7 V. A gradual transition of the ferroelectricity with an increasing crystallization temperature for the gate-last process was presented. The excellent data retention are the ${\sim }\textsf {2}\times \textsf {10}^{\textsf {4}}$ ON/OFF ratio and 0.67 V extrapolated to ten years with VP/E = ±4.8 V. The MW remains >0.2 V after 106 cycles for read and vanishes with cycles of 103−104 for write, which is the bottleneck for ferroelectric (FE)-type memories. The mechanism of retention and endurance is discussed. The characteristic of this letter is an unaffected coercive-field (~1 MV/cm) with scaling FE-HZO down to 5-nm thickness, which is beneficial for reducing the operation voltage. A comparable performance with thick HZO (>5 nm) on high data retention and endurance with low voltage for read is achieved. The ultrathin FE layer proposes a realistic emerging memory for 1T architecture. [ABSTRACT FROM AUTHOR]

The correlation between microstructures and magnetic properties of Pr-Fe-B thin films with thickness in the range of 25-150 nm sputtered on Ta underlayer buffered glass substrates was investigated. The films with thickness of 50-125 nm showed Pr2Fe14B phase with (004) preferred orientation. Perpendicular magnetic properties, including perpendicular magnetic anisotropy, coercivity ((Hc˔)2T), remanence ratio ((Mr/M2T)˔), and energy product [(BH)max˔]2T were improved with increment of magnetic layer thickness to 150 nm. Higher (Hc˔)2T of 10.3 kOe and energy product [(BH)max˔]2T of 19.8 MGOe were attained in the film with the thicker thickness, in turn resulted from fine microstructure and impeded domain wall motion due to nonmagnetic Pr-rich grain boundary phase as a pinning site. [ABSTRACT FROM AUTHOR]