Raymond Josephus Engelbart Hueting

The Charge Plasma P-N Diode

A simulation study on a new rectifier concept is presented. This device basically consists of two gates with different workfunctions on top of a thin intrinsic or lowly doped silicon body. The workfunctions and layer thicknesses are chosen such that an electron plasma is formed on one side of the silicon body and a hole plasma on the other, i.e., a charge plasma p-n diode is formed in which no doping is required. Simulation results reveal a good rectifying behavior for well-chosen gate workfunctions and device dimensions. This concept could be applied for other semiconductor devices and materials as well in which doping is an issue.

Fabrication and Characterization of the Charge-Plasma Diode

We present a new lateral Schottky-based rectifier called the charge-plasma diode realized on ultrathin silicon-on-insulator. The device utilizes the workfunction difference between two metal contacts, palladium and erbium, and the silicon body. We demonstrate that the proposed device provides a low and constant reverse leakage-current density of about 1 fA/μm with ON/OFF current ratios of around 107 at 1-V forward bias and room temperature. In the forward mode, a current swing of 88 mV/dec is obtained, which is reduced to 68 mV/dec by back-gate biasing.

On the Trade-Off Between Quality Factor and Tuning Ratio in Tunable High-Frequency Capacitors

A benchmark of tunable and switchable devices at microwave frequencies is presented on the basis of physical limitations to show their potential for reconfigurable cellular applications. Performance limitations are outlined for each given technology focusing on the quality factor (Q) and tuning ratio (eta) as figures of merit. The state of the art in terms of these figures of merit of several tunable and switchable technologies is visualized and discussed. If the performance of these criteria is not met, the application will not be feasible. The quality factor can typically be traded off for tuning ratio. The benchmark of tunable capacitor technologies shows that transistor-switched capacitors, varactor diodes, and ferroelectric varactors perform well at 2 GHz for tuning ratios below 3, with an advantage for GaAs varactor diodes. Planar microelectromechanical capacitive switches have the potential to outperform all other technologies at tuning ratios higher than 8. Capacitors based on tunable dielectrics have the highest miniaturization potential, whereas semiconductor devices benefit from the existing manufacturing infrastructure.

Analysis of the subthreshold current of pocket or halo-implanted nMOSFETs

In this work, we analyzed the subthreshold current (ID) of pocket implanted MOSFETs using extensive device simulations and experimental data. We present an analytical model for the subthreshold current applicable for any type of FET and show that the subthreshold current of nMOSFETs, which is mainly due to diffusion, is determined by the internal two-dimensional hole distribution across the device. This hole distribution is affected by the electric potential of the gate and the doping concentration in the channel. The results obtained allow accurate modelling of the subthreshold current of future generation MOS devices

Opto-electronic modeling of light emission from avalanche-mode silicon p+n junctions

This work presents the modeling of light emission from silicon based pþn junctions operating in avalanche breakdown. We revisit the photon emission process under the influence of relatively high electric fields in a reverse biased junction (>105 V/cm). The photon emission rate is described as a function of the electron temperature Te, which is computed from the spatial distribution of the electric field. The light emission spectra lie around the visible spectral range (k 300–850 nm), where the peak wavelength and the optical intensity are both doping level dependent. It is theoretically derived that a specific minimum geometrical width (170 nm) of the active region of avalanche is required, corresponding to a breakdown voltage of 5V, below which the rate of photon emission in the desired spectrum drops. The derived model is validated using experimental data obtained from ultra-shallow pþn junctions with low absorption through a nm-thin pþ region and surface coverage of solely 3 nm of pure boron. We observe a peak in the emission spectra near 580 nm and 650 nm for diodes with breakdown voltages 7V and 14 V, respectively, consistent with our model.

Dimensional scaling effects on transport properties of ultrathin body p-i-n diodes

Device scaling has been a subject of research for both optoelectronics and electronics. In order to investigate the electronic properties of scaled devices we studied lateral p-i-n structures using thin silicon on insulator (SOI) or poly-Si layers of varying dimension. With the help of these structures we try to explain the size dependencies on electronic transport properties. Further, we also propose a new device concept called charge plasma diode.

Piezoelectric Strain Modulation in FETs

We report on a feature for the transistor, a piezoelectric layer to modulate the strain in the channel. The strain is proportional to the gate-source voltage, and thus increases as the device is turned on. As a result, the device has the leakage current of a relaxed device and the lower threshold voltage of a strained device. Our results, obtained by combining electrical and mechanical simulations, demonstrate that strain modulation can result in a 9 mV/decade smaller subthreshold swing for a FinFET.

Optimized reflector stacks for solidly mounted bulk acoustic wave resonators

The quality factor (Q) of a solidly mounted bulk acoustic wave resonator (SMR) is limited by substrate losses, because the acoustic mirror is traditionally optimized to reflect longitudinal waves only. We propose two different design approaches derived from optics to tailor the acoustic mirror for effective reflection of both longitudinal and shear waves. The first one employs the stopband theory in optics; the second one takes advantage of the periodic nature of reflection spectra in a Bragg reflector: the diffraction grating design approach. The optimized design using stopband theory reaches a calculated minimum transmission of -25 dB and -20 dB at resonance frequency for longitudinal and shear waves, respectively, for various practical reflector material combinations. Using the diffraction grating approach, a near quarter-wave performance is maintained for longitudinal waves, whereas shear waves reach minimum transmission below -26 dB. However, this design does necessitate relatively thick layers. The experimental results show good agreement with finite element models (FEM). The extracted 1-D Q for the realized shear optimized devices was increased to around 3300.

Extracting Energy Band Offsets on Long-Channel Thin Silicon-on-Insulator MOSFETs

Structural quantum confinement in long-channel thin silicon-on-insulator MOSFETs has been quantified using the temperature dependence of the subthreshold current. The results were compared with the shifts in the threshold voltage. Data were obtained from simulations after initial verification with experimental data. This study demonstrates that, with the temperature dependence of the subthreshold current, shifts in the valence and conduction band edge can be extracted distinctively from changes in mobility and density of states (DOS), making this method more accurate in assessing the impact of structural quantum confinement than the commonly used threshold voltage method. Furthermore, we show that, with additional C-V data, a possible change in mobility and DOS can be disentangled.

Design optimization of field-plate assisted RESURF devices

A mathematical model for optimizing the 2-D potential distribution in the drift region of field-plate (FP)-assisted RESURF devices (Fig. 1) is presented. The proposed model extends earlier work [1-2] by including top-bottom dielectric asymmetry (typical in SOI devices [3]), non-zero field plate potentials VFP and grading of design parameters other than drift region doping. This generally-applicable, TCAD-verified [4], model provides a guideline for optimizing the drain extension in a wide range of FP-assisted RESURF devices.