High on-state current p-type tunnel effect transistor based on doping modulation

To solve the problem of the low on-state current in p-type tunnel field-effect transistors(p-TFETs),this paper analyzes the mechanism of adjusting the tunneling current of a TFET device determined by studying the influence of the peak position of ion implantation on the potential of the p-TFET device surface and the width of the tunneling barrier.Doping-regulated silicon-based high on-state p-TFET devices are designed and fabricated,and the test results show that the on-state current of the fabricated devices can be increased by about two orders of magnitude compared with the current of other devices with the same structure.This method provides a new idea for the realization of high on-state current TFET devices.

Modulation doping of p-type Cu_(12)Sb_(4)S_(13)toward improving thermoelectric performance

The commercial viability of thermoelectric(TE)devices relies heavily on two factors:cost reduction and efficiency enhancement.In this study,we first produce p-type Cu_(12)Sb_(4)S_(16-x)(x=0,3,4)using a low-temperature bottom-up approach and demonstrate Cu_(12)Sb_(4)S_(13)to show the best TE performance among the three tested compositions.Subsequently,the TE energy conversion efficiency of Cu_(12)Sb_(4)S_(13)is further enhanced by optimizing its electronic band structure through the incorporation of small amounts of tel-lurium.At an optimal Te content of 5 mol%,more than a twofold increase in the TE figure of merit(zT)is obtained.To gain insight into the mechanism of improvement on the transport properties of the mate-rial,we compare the interphase transport mechanism by incorporating nanodomains of different metals(Ag and Cu)into the Cu_(12)Sb_(4)S_(13)matrix.The improved electrical conductivity obtained with Cu_(12)Sb_(4)S_(13)-Te nanocomposites is attributed to a charge flooding of the Cu_(12)Sb_(4)S_(13)surface.In contrast,excessive down-ward band-bending at the interphases of Ag/Cu metal-semiconductor drastically reduces the electrical conductivity.Besides,a weighted mobility(μw)analysis shows a dominant thermal activation of carri-ers in Cu_(12)Sb_(4)S_(13)-Te nanocomposites.In this material,a strong decrease in lattice thermal conductivity is also found,which is associated with a phonon-carrier scattering mechanism.Our work shows the impor-tance of proper band-engineering in TE nanocomposites to decouple electrical and thermal transport to enhance TE performance,and the efficacy ofμw for electrical and thermal transport analysis.

Experimental observation of pseudogap in a modulation-doped Mott insulator:Sn/Si(111)-(√3×√3)R30°

Unusual quantum phenomena usually emerge upon doping Mott insulators.Using a molecular beam epitaxy system integrated with cryogenic sc√annin√g tunneling microscope,we investigate the electronic structure of a modulation-doped Mott insulator Sn/Si(111)-(√3×√3)R30°.In underdoped regions,we observe a universal pseudogap opening around the Fermi level,which changes little with the applied magnetic field and the occurrence of Sn vacancies.The pseudogap gets smeared out at elevated temperatures and alters in size with the spatial confinement of the Mott insulating phase.Our findings,along with the previously observed superconductivity at a higher doping level,are highly reminiscent of the electronic phase diagram in the doped copper oxide compounds.

High-voltage super-junction lateral double-diffused metal-oxide semiconductor with a partial lightly doped pillar

A novel super-junction lateral double-diffused metal-oxide semiconductor （SJ-LDMOS） with a partial lightly doped P pillar （PD） is proposed. Firstly, the reduction in the partial P pillar charges ensures the charge balance and suppresses the substrate-assisted depletion effect. Secondly, the new electric field peak produced by the P/P junction modulates the surface electric field distribution. Both of these result in a high breakdown voltage （BV）. In addition, due to the same conduction paths, the specific on-resistance （Ron,sp） of the PD SJ-LDMOS is approximately identical to the conventional SJ-LDMOS. Simulation results indicate that the average value of the surface lateral electric field of the PD SJ-LDMOS reaches 20 V/μm at a 15 μm drift length, resulting in a BV of 300 V.

Photo-Doped Active Electrically Controlled Terahertz Modulator

We demonstrate an electric-controlled terahertz（THz） modulator which can be used to realize amplitude modulation of terahertz waves with slight photo-doping. The THz pulse transmission was efficiently modulated by electrically controlling the monolayer silicon-based device. The modulation depth reached 100% almost when the applied voltage was 7V at an external laser intensity of 0.6W/cm2. The saturation voltage reduced with the increase of the photo-excited intensity. In a THz continuous wave（CW）system, a significant fall in both THz transmission and reflection was also observed with the increase of applied voltage. This reduction in the THz transmission and reflection was induced by the absorption for electron injection. The results show that a high-efficiency and high modulation depth broadband electric-controlled terahertz modulator in a pure Si structure has been realized.

Guest Editorial——TTA Special Section on Terahertz Functional Devices

Terahertz（THz）radiation has been extensively investigated in recent years due to its potential applications in communication,homeland security,safety inspection,sensing,and imaging.For a common THz system,three parts are quite important：THz sources,THz detectors,and THz functional devices.

Highly efficient silicon light emitting diodes produced by doping engineering

This paper reviews our recent progress on silicon （Si） pn junction light emitting diodes with locally doping engineered carrier potentials. Boron implanted Si diodes with dislocation loops have electroluminescence （EL） quantum efficiency up to 0.12%, which is two orders of magnitude higher than those without dislocations. Boron gettering along the strained dislocation lines produces locally p-type spike doping at the dislocations, which have potential wells for bounding spatially indirect excitons. Thermal dissociation of the bound excitons releases free carriers, leading to an anomalous increase of the band to band luminescence with increasing tempera- ture. Si light emitting diodes with external quantum efficiency of 0.2% have been also demonstrated by implementation of pnpn modulation doping arrays.

Realizing high thermoelectric performance for p-type SiGe in medium temperature region via TaC compositing

SiGe is recognised as an excellent thermoelectric material with superior mechanical properties and thermal stability in regions with high temperatures.This study explores a novel strategy for coregulating thermoelectric transport parameters to achieve high thermoelectric properties of p-type SiGe in the mid-temperature region by incorporating nano-TaC into SiGe combined ball milling with spark plasma sintering.By optimizing the amount of TaC in the SiGe matrix,the power factors were significantly increased due to the modulation doping effect based on the work function matching of SiGe with TaC.Simultaneously,the ensemble effect of the nanostructure leads to a significant decrease in thermal conductivity.Thus,a high ZT of 1.06 was accomplished at 873 K,which is 64%higher than that of typical radioisotope thermoelectric generator.Our research offers a novel strategy for expanding and enhancing the thermoelectric properties of SiGe materials in the medium temperature range.

Nodeless pairing in superconducting copper-oxide monolayer films on BieSreCaCueO8＋δ

The pairing mechanism of high-temperature superconductivity in cuprates remains the biggest unresolved mystery in condensed matter physics. To solve the problem, one of the most effective approaches is to investigate directly the superconducting CuO2 layers. Here, by growing CuO2 monolayer films on Bi2Sr2CaCu2O8＋δ substrates, we identify two distinct and spatially separated energy gaps centered at the Fermi energy, a smaller U-like gap and a larger V-like gap on the films, and study their interactions with alien atoms by low-temperature scanning tunneling microscopy. The newly discovered U-like gap exhibits strong phase coherence and is immune to scattering by K, Cs and Ag atoms, suggesting its nature as a nodeless superconducting gap in the CuO2 layers, whereas the V-like gap agrees with the well-known pseudogap state in the underdoped regime. Our results support an s-wave superconductivity in Bi2Sr2CaCu2O8＋δ, which, we pro- pose, originates from the modulation-doping resultant twodimensional hole liquid confined in the CuO2 layers.

Low-loss high-extinction-ratio single-drive push-pull silicon Michelson interferometric modulator

We demonstrate a high-speed silicon carrier-depletion Michelson interferometric（MI）modulator with a low onchip insertion loss of 3 dB.The modulator features a compact size of 〈1 mm2 and a static high extinction ratio of 〉30 dB.The Vπ·Lπ of the MI modulator is 0.95–1.26 V·cm under a reverse bias of -1 to-8 V,indicating a high modulation efficiency.Experimental results show that a 4-level pulse amplitude modulation up to 20 Gbaud is achieved with a bit error rate of 6×10-3,and a 30 Gb/s binary phase-shift-keying modulation is realized with an error vector magnitude of 25.8%.