Search

We have compared the device performance of In0.7Ga0.3As HfO2 gate dielectric tunneling field-effect-transistors (TFETs) using p++/i or p++/n+ tunneling junctions. Devices with p++/n+ tunneling junctions show 61% and 20% higher current at Vg-Vth=0.5 and 2 V compared to the ones with p++/i junctions. These p++/n+ TFETs exhibit an on-current of 60 μA/μm and a minimum subthreshold swing of 84 mV/dec. Device characteristics of TFETs using p++/n+ tunneling diodes with various n+ region doping concentrations have been simulated, results indicate the doping concentration of the n+ region plays an important role in determining the on-current and providing a well gate-controlled tunneling behavior. [ABSTRACT FROM AUTHOR]

Performance improvement of InGaAs buried channel metal-oxide-semiconductor field-effect-transistors (MOSFETs) has been achieved by inserting InAs layer and properly designing the inserted layer position. In0.7Ga0.3As and InAs channel buried channel MOSFETs were fabricated and analyzed including drive current, transconductance, effective mobility, and subthreshold swing. All InAs buried channel devices show good off-state and saturation property. By inserting InAs in the middle of InGaAs channel (InGaAs/InAs/InGaAs channel), 37% enhancement of high field effective channel mobility was achieved over devices with pure InGaAs channel. Devices with InAs inserted in the middle exhibits peak effective channel mobility around 6140 cm2/V s and subthreshold swing of 107 mV/dec. [ABSTRACT FROM AUTHOR]

In this letter, we demonstrate a high performance In0.53Ga0.47As channel n-type metal-oxide-semiconductor field effect transistor with silicon interface passivation layer (IPL) and HfO2 gate oxide. Owing to the effectiveness of Si IPL on improving the interface quality, good device characteristics have been obtained, including the peak transconductance of 7.7 mS/mm (Lg=5 μm and Vd=50 mV), drive current of 158 mA/mm (Lg=5 μm, Vgs=Vth+2 V, and Vd=2.5 V), and the peak effective channel mobility of 1034 cm2/V s. As an important factor on device design, the impact of silicon IPL thickness on the transistor characteristics has been investigated. [ABSTRACT FROM AUTHOR]

We present InP metal-oxide-semiconductor capacitors (MOSCAPs) and metal-oxide-semiconductor field-effect transistors (MOSFETs) with stacked HfAlOx/HfO2 gate dielectric deposited by atomic layer deposition. Compared with single HfO2, the use of stacked HfAlOx/HfO2 results in better interface quality with InP substrate, as illustrated by smaller frequency dispersion and lower leakage current density. The equivalent oxide thickness of MOSCAPs with 10 Å HfAlOx/25 Å HfO2 stacked gate dielectric is 12 Å. The MOSFETs with this gate dielectric achieve two times higher transconductance than those with single 35 Å HfO2. They also exhibit drive current of 60 mA/mm and subthreshold swing of 83 mV/decade for 5 μm gate length. [ABSTRACT FROM AUTHOR]

We present gallium arsenide (GaAs) metal-oxide-semiconductor capacitors (MOSCAPs) with a thin HfO2 gate dielectric and a thin germanium nitride (GexNy) interfacial passivation layer (IPL). TaN/HfO2/GexNy/GaAs MOSCAPs show a low interface state density and a thin equivalent oxide thickness (1.6 nm). Compared to GaAs MOSCAPs with germanium (Ge) IPL, the GexNy IPL has a smaller slow trap density, which is confirmed by improved C-V characteristics without humps near the flatband voltage. The lower rate of flatband voltage shift and gate leakage decreasing under constant gate voltage stress were also demonstrated in GaAs MOSCAPs with GexNy IPL than the Ge IPL. [ABSTRACT FROM AUTHOR]

We analyze the anomalous I-V behavior in SiN prepared by plasma enhanced chemical vapor deposition for use as a gate insulator in AlGaN/GaN metal insulator semiconductor heterostructure filed effect transistors (HFETs). We observe leakage current across the dielectric with opposite polarity with respect to the applied electric field once the voltage sweep reaches a level below a determined threshold. This is observed as the absolute minimum of the leakage current does not occur at minimum voltage level (0 V) but occurs earlier in the sweep interval. Curve-fitting analysis suggests that the charge-transport mechanism in this region is Poole-Frenkel current, followed by Schottky emission due to band bending. Despite the current anomaly, the sample devices have shown a notable reduction of leakage current of over 2 to 6 order of magnitudes compared to the standard Schottky HFET. We show that higher pressures and higher silane concentrations produce better films manifesting less trapping. This conforms to our results that we reported in earlier publications. We found that higher chamber pressure achieves higher sheet carrier concentration that was found to be strongly dependent on the trapped space charge at the SiN/GaN interface. This would suggest that a lower chamber pressure induces more trap states into the SiN/GaN interface. [ABSTRACT FROM AUTHOR]

In this work, the experimental impact of SF6 plasma treatment on the performance of InP metal-oxide-semiconductor field-effect transistors is presented. S and F are incorporated into atomic layer deposited HfO2 via postgate SF6 plasma treatment. The decreased subthreshold swing, gate leakage (Ig), and increased effective channel mobility (μeff) indicate that better interface and bulk oxide quality have been achieved with SF6 plasma treatment due to the formation of stronger Hf-F bonds. Drive current (Id), transconductance (Gm), and effective channel mobility (μeff) are improved by 22.3%, 35%, and 35%, respectively, compared with those of control devices. [ABSTRACT FROM AUTHOR]

We present the design, architecture, and detailed performance of a three-dimensional (3D) underwater acoustic carpet cloak (UACC). The proposed system of the 3D UACC is an octahedral pyramid, which is composed of periodical steel strips. This underwater acoustic device, placed over the target to hide, is able to manipulate the scattered wavefront to mimic a reflecting plane. The effectiveness of the prototype is experimentally demonstrated in an anechoic tank. The measured acoustic pressure distributions show that the 3D UACC can work in all directions in a wide frequency range. This experimental verification of 3D device paves the way for guidelines on future practical applications. [ABSTRACT FROM AUTHOR]

The primary goal of this work is to investigate the capability of gate oxide scaling down in HfO2-based GaAs metal-oxide-semiconductor capacitor (MOSCAP) using a thin germanium (Ge) interfacial passivation layer (IPL). With HfO2 of 45–50 Å, an equivalent oxide thickness (EOT) of 8.7 Å was achieved with a low gate oxide leakage current density (Jg) of (2–4)×10-3 A/cm2 at VG-VFB=1.0 V. This is the thinnest EOT thickness ever reported for high-k III-V MOSCAPs. On the other hand, with thicker HfO2 of 100–110 Å, an EOT of 20–22 Å with Jg of (2–4)×10-6 A/cm2 at VG-VFB=1.0 V was attained. In addition, breakdown voltages of gate oxide and hysteresis characteristics according to different thicknesses of HfO2 were studied. The results indicate that a Ge IPL and thin HfO2 enable excellent gate oxide scaling down in GaAs system. [ABSTRACT FROM AUTHOR]

In this letter, we developed an original innovative wiping-rubbing method to fabricate flexible transparent conductive films (TCFs) based on graphene nanosheets. We achieved this by using only commercial graphite block and polycarbonate film as raw materials, through a cost effective and ultrafast room temperature wiping-rubbing process (within 2 min). The properties of our flexible TCFs were competitive when comparing with literature reported graphene TCFs. Our flexible TCFs showed enough surface stability under a series of surface destructive treatments. The physical mechanism aspects of wiping-rubbing processes and surface stability were discussed. [ABSTRACT FROM AUTHOR]