High Frequency Gate Research Articles

Embedded metal and L-shaped oxide layers in silicon on insulator MESFETs: higher electric field tolerance and lower high frequency gate capacitances

Embedded metal and L-shaped oxide layers in silicon on insulator MESFETs: higher electric field tolerance and lower high frequency gate capacitances

Gate Voltage Pulse Rising Edge Dependent Dynamic Hot Carrier Degradation in Poly-Si Thin-Film Transistors

Dynamic degradation becomes a critical issue for thin-film transistors (TFTs) used in emerging new displays driven by high frequency gate voltage ${V}_{\text {G}}$ pulses. In this study, ${V}_{\text {G}}$ pulse rising edge dependent dynamic hot carrier degradation of poly-Si TFTs is investigated. It is demonstrated that rising edge of ${V}_{\text {G}}$ pulses which swing within the OFF-state of TFTs causes the degradation, while that of normal ${V}_{\text {G}}$ pulses which switch between the ON and OFF states across the flat band voltage ${V}_{\text {FB}}$ of TFTs does not. Based on transient TCAD simulation, the underlying mechanism of rising edge dependent degradation is proposed, which is based on the non-equilibrium PN junction degradation model previously proposed to explain ${V}_{\text {G}}$ pulse falling edge dependent degradation of poly-Si TFTs. Hence, the dynamic degradation model of poly-Si TFTs related to both rising and falling edge of the ${V}_{\text {G}}$ pulses can be unified now, which is applicable to fast gate pulses with steep rising and/or falling edges in sub- $\mu \text{s}$ level.

Research on GaN-Based RF Devices: High-Frequency Gate Structure Design, Submicrometer-Length Gate Fabrication, Suppressed SCE, Low Parasitic Resistance, Minimized Current Collapse, and Lower Gate Leakage

As an important part of wireless communication systems, the technology of RF devices and circuits has been progressing rapidly. For high-frequency and high-power applications, vacuum electronic devices (e.g., traveling wave tubes) have been widely used, although the vacuum tube is large in size and hard to integrate.

High-frequency gate manipulation of a bilayer graphene quantum dot

We report transport data obtained for a double-gated bilayer graphene quantum dot. In Coulomb blockade measurements, the gate dielectric Cytop(TM) is found to provide remarkable electronic stability even at cryogenic temperatures. Moreover, we demonstrate gate manipulation with square shaped voltage pulses at frequencies up to 100 MHz and show that the signal amplitude is not affected by the presence of the capacitively coupled back gate.

Direct measurement of the intrinsic RC roll-off in a radio frequency single electron transistor operated as a microwave mixer

By operating the radio frequency single electron transistor (rf-SET) as a mixer we present measurements in which the RC roll-off of the tunnel junctions is observed at high frequencies. Our technique makes use of the nonlinear rf-SET transconductance to mix high frequency gate signals and produce difference-frequency components that fall within the bandwidth of the rf-SET. At gate frequencies >15GHz the induced charge on the rf-SET island is altered on time scales faster than the inverse tunnel rate, preventing mixer operation. We suggest the possibility of utilizing this technique to sense high frequency signals beyond the usual rf-SET bandwidth.

A new oxide-trap based on charge-pumping (OTCP) extraction method for irradiated MOSFET devices: part II (low frequencies)

In this paper, we propose a new extraction method of radiation-induced oxide-trap density (/spl Delta/N/sub ot/), called Oxide-Trap based on Charge-Pumping (OTCP). This part presents the HF-OTCP method, which relies on high-frequency (HF) standard charge-pumping measurement. By applying an HF gate voltage signal, we avoid the border-trap effect in CP current (I/sub cp/) measurements. Hence, I/sub cp/ will be only due to the interface-trap contribution. We establish, using the HF-OTCP method, that /spl Delta/N/sub ot/ is only dependent on /spl Delta/V/sub th/ (threshold voltage shift) and /spl Delta/I/sub cpm/ (increase of maximum CP current), where /spl Delta/I/sub cpm/ is caused by radiation-induced interface-trap increase (/spl Delta/N/sub it/). We also clearly show that /spl Delta/V/sub th/ and /spl Delta/I/sub cpm/ can be obtained from lateral and vertical shifts of Elliot's charge-pumping curves, respectively. Thus, this new procedure allows the determination of /spl Delta/N/sub ot/ without needing any additional techniques. Finally, this procedure can be used in rapid hardness assurance test to evaluate both radiation-induced oxide and interface traps.

Recombination current measurements in the space charge region of MOS field-induced pn junctions

Electrically active defects in the device region are routinely monitored by CV measurements of reverse-biased field-induced (FI) pn junctions in MOS structures. While useful, this approach is sensitive only to near mid gap defects. Here, we demonstrate a method for interrogation of forward-biased FI pn junctions, which can reveal defect levels over a significantly wider region of the band gap. The method proposed is based on a simultaneous measurement of the gate current and the high frequency gate capacitance in non-equilibrium non-steady state in response to a linear gate voltage ramp which drives the MOS capacitor from inversion equilibrium towards accumulation. This recombination-sensitive technique enables a self-consistent determination of the forward current–voltage characteristic of the FI pn junction. It makes a wider range of important impurities, especially metallic contaminants, accessible to detection by MOS CV approaches. Since the approach satisfies the low-injection condition, the results can be directly related to the properties of the defect centres, thus facilitating defect identification and control.

Impact of Heat Transport on the Electrical Characteristics of a GaAs MESFET under Periodic Steady-State Operation.

Two dimensional numerical calculation of heat generation and transport in GaAs MESFETs with high frequency gate bias has been performed. In order to study the conjugate nature of electronic and thermal phenomena in the semiconductor devices, electron particles, momentum and energy equations, and the energy equations of optical and acoustic phonons as well as Poisson equation are solved simultaneously. Calculated results exhibited the effect of temperature distributions to the current charactreistics as high frequency gate voltage variation.

Modeling of GaAs/AlGaAs MODFET inverters and ring oscillators

Detailed understanding of the MODFET inverter chains is lacking and present designs are based on ground rules developed by trial and error. We developed a simple and straightforward model for the current-voltage characteristics using results from numerical solutions of the quantum mechanical problem; this model agrees very well with experimental results obtained in our laboratory. High-frequency gate capacitance voltage characteristics for a wide gate voltage range was modeled for the first time in a similar fashion. These models were used to simulate a chain of inverters at 77 and 300 K for a wide range of supply voltage and load current. The maximum device speed is obtained for small supply voltages, ≤ 1 V both at 300 and 77 K, where the effects of transconductance degradation and large gate capacitance are minimized. The devices exhibit under 10-ps switching times both at 300 and 77 K, with 77 K logic swing being much larger. The results are in qualitative agreement with the reported experimental results.