In this paper, a dopingless fin-shaped SiGe channel TFET (DF-TFET) is proposed and studied. To form a high-efficiency dopingless line tunneling junction, a fin-shaped SiGe channel and a gate/source overlap are induced. Through these methods, the DF-TFET with high on-state current, switching ratio of 12 orders of magnitude and no obvious ambipolar effect can be obtained. High κ material stack gate dielectric is induced to improve the off-state leakage, interface characteristics and the reliability of DF-TFET. Moreover, by using the dopingless channel and fin structure, the difficulties of doping process and asymmetric gate overlap formation can be resolved. As a result, the structure of DF-TFET can possess good manufacture applicability and remarkably reduce footprint. The physical mechanism of device and the effect of parameters on performance are studied in this work. Finally, on-state current (I_ON) of 58.8 μA/μm, minimum subthreshold swing of 2.8 mV/dec (SS_min), average subthreshold swing (SS_avg) of 18.2 mV/dec can be obtained. With improved capacitance characteristics, cutoff frequency of 5.04 GHz and gain bandwidth product of 1.29 GHz can be obtained. With improved performance and robustness, DF-TFET can be a very attractive candidate for ultra-low-power applications.

Label-free biomolecular sensors have been widely studied due to their simple operation. L-shaped tunneling field-effect transistors (LTFETs) are used in biosensors due to their low subthreshold swing, off-state current, and power consumption. In a dielectric-modulated LTFET (DM-LTFET), a cavity is trenched under the gate electrode in the vertical direction and filled with biomolecules to realize the function of the sensor. A 2D simulator was utilized to study the sensitivity of a DM-LTFET sensor. The simulation results show that the current sensitivity of the proposed structure could be as high as 2321, the threshold voltage sensitivity could reach 0.4, and the subthreshold swing sensitivity could reach 0.7. This shows that the DM-LTFET sensor is suitable for a high-sensitivity, low-power-consumption sensor field.

In this paper, a dual metallic material gate heterostructure junctionless tunnel field-effect transistor (DMMG-HJLTFET) is proposed and investigated. We use the Si/SiGe heterostructure at the source/channel interface to improve the band to band tunneling (BTBT) rate, and introduce a sandwich stack (GaAs/Si/GaAs) at the drain region to suppress the OFF-state current and ambiplolar current. Simultaneously, to further decrease ambipolar current, the gate electrode is divided into three parts namely auxiliary gate (M1), control gate (M2), and tunnel gate (M3) with workfunctions Φ_M1, Φ_M2 and Φ_M3, respectively, where Φ_M1 = Φ_M3 < Φ_M2. Simulation results indicate that DMMG-HJLTFET provides superior performance in terms of logic and analog/RF as compared with other possible combinations, the ON-state current of the DMMG-HJLTFET increases up to $9.04\times 10^{-6}$ A/μm, and the maximum g_m (which determine the analog performance of devices) of DMMG-HJLTFET is $1.11\times 10^{-5}$ S/μm at 1.0V drain-to-source voltage (Vds). Meanwhile, RF performance of devices depends on the cut-off frequency (f_T) and gain bandwidth (GBW), and DMMG-HJLTFET could achieve a maximum f_T of 5.84 GHz, and a maximum GBW of 0.39 GHz, respectively.

It is well known that the vertical tunnel field effect transistor (TFET) is easier to fabricate than the conventional lateral TFETs in technology. Meanwhile, a lightly doped pocket under the source region can improve the subthreshold performance of the vertical TFETs. This paper demonstrates a dual material gate heterogeneous dielectric vertical TFET (DMG-HD-VTFET) with a lightly doped source-pocket. The proposed structure adopts a GaSb/GaAs_0.5Sb_0.5 heterojunction at the source and pocket to improve the band-to-band tunneling (BTBT) rate; at the same time, the gate electrode is divided into two parts, namely a tunnel gate (M1) and control gate (M2) with work functions Φ_M1 and Φ_M2, where Φ_M1 > Φ_M2. In addition, further performance enhancement in the proposed device is realized by a heterogeneous dielectric corresponding to a dual material gate. Simulation results indicate that DMG-HD-VTFET and HD-VTFET possess superior metrics in terms of DC (Direct Current) and RF (Radio Frequency) performance as compared with conventional VTFET. As a result, the ON-state current of 2.92 × 10⁻⁴ A/μm, transconductance of 6.46 × 10⁻⁴ S/μm, and average subthreshold swing (SS_ave) of 18.1 mV/Dec at low drain voltage can be obtained. At the same time, DMG-HD-VTFET could achieve a maximum f_T of 459 GHz at 0.72 V gate-to-source voltage (V_gs) and a maximum gain bandwidth (GBW) of 35 GHz at V_gs = 0.6 V, respectively. So, the proposed structure will have a great potential to boost the device performance of traditional vertical TFETs.

Biosensors based on tunnel FET for label-free detection in which a nanogap is introduced under gate electrode to electrically sense the characteristics of biomolecules, have been studied widely in recent years. In this paper, a new type of heterostructure junctionless tunnel FET biosensor with an embedded nanogap is proposed, in which the control gate consists of two parts, namely the tunnel gate and auxiliary gate, with different work functions; and the detection sensitivity of different biomolecules can be controlled and adjusted by the two gates. Further, a polar gate is introduced above the source region, and a P+ source is formed by the charge plasma concept by selecting appropriate work functions for the polar gate. The variation of sensitivity with different control gate and polar gate work functions is explored. Neutral and charged biomolecules are considered to simulate device-level gate effects, and the influence of different dielectric constants on sensitivity is also researched. The simulation results show that the switch ratio of the proposed biosensor can reach 10⁹, the maximum current sensitivity is 6.91 × 10², and the maximum sensitivity of the average subthreshold swing (SS) is 0.62.

High-spin states in ${}_{}{}^{68}{}_{}{}^{}\mathrm{Ge}$ and ${}_{}{}^{72}{}_{}{}^{}\mathrm{Se}$ have been studied by in-beam, gamma-ray spectroscopy. In ${}_{}{}^{68}{}_{}{}^{}\mathrm{Ge}$ the three known bands beginning at $8^{+}$ are found to exhibit crossing transitions and other new positive-parity bands are discovered to feed into them. In ${}_{}{}^{72}{}_{}{}^{}\mathrm{Se}$ only a single positive-parity yrast band is seen to high spin. Detailed, more realistic microscopic model calculations have been carried out for ${}_{}{}^{68}{}_{}{}^{}\mathrm{Ge}$ and ${}_{}{}^{72}{}_{}{}^{}\mathrm{Se}$. There is striking agreement between the calculations and the new data for ${}_{}{}^{68}{}_{}{}^{}\mathrm{Ge}$, including a predicted new band with superdeformation, β∼0.42. The calculations for ${}_{}{}^{72}{}_{}{}^{}\mathrm{Se}$ predict similar multiple band structures that are not seen experimentally.