An Initial study on The Reliability of Power Semiconductor Devices

An initial literature study combined with some basic comparative simulations has been performed on different electricfield modulation techniques and the subsequent reliability issues are reported for power semiconductor devices. An explanation of the most important power device metrics such as the offstate breakdown (BV) and specific on-resistance (RON) will be given, followed by a short overview of some of the electrostatic techniques (fieldplates, RESURF e.g. [1]) used to suppress peak electric fields. Furthermore it will be addressed that the high current operation of these devices results in shifting electric field peaks (Kirk effect [2], [3]) and as such different avalanche behavior, resulting in (gate oxide) reliability issues unlike those of conventional CMOS

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

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-oninsulator. 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

Investigation of Pd/MoO_x/n-Si diodes for bipolar transistor and light-emitting device applications

Sub-stoichiometric molybdenum oxide (MoO x) has recently been investigated for application in high efficiency Si solar cells as a "hole selective"contact. In this paper, we investigate the electrical and light-emitting properties of MoO x-based contacts on Si from the viewpoint of realizing functional bipolar devices such as light-emitting diodes (LEDs) and transistors without any impurity doping of the Si surface. We realized diodes on n-type Si substrates using e-beam physical vapor deposition of Pd/MoO x contacts and compared their behavior to implanted p +n-Si diodes as a reference. In contrast to majority-carrier dominated conduction that occurs in conventional Schottky diodes, Pd/MoO x/n-Si diodes show minority-carrier dominated charge transport with I-V, C-V, and light-emitting characteristics comparable to implanted counterparts. Utilizing such MoO x-based contacts, we also demonstrate a lateral bipolar transistor concept without employing any doped junctions. A detailed C-V analysis confirmed the excessive band-bending in Si corresponding to a high potential barrier (> - > 0.90 V) at the MoO x/n-Si interface which, along with the observed amorphous SiO x(Mo) interlayer, plays a role in suppressing the majority-carrier current. An inversion layer at the n-Si surface was also identified comprising a sheet carrier density greater than 8.6 × 10 11 cm - 2, and the MoO x layer was found to be conductive though with a very high resistivity in the 10 4 ω-cm range. We refer to these diodes as metal/non-insulator/semiconductor diodes and show with our device simulations that they can be mimicked as high-barrier Schottky diodes with an induced inversion layer at the interface

Monofilament assessment of neuropathy in a community diabetes clinic

Objective. To compare the detection of diabetic neuropathy using monofilament, cotton wool, pinprick, vibration sense and symptom evaluation.Setting. The diabetes clinic of a community hospital.Methods. Two examiners evaluated 89 women with diabetes mellitus (DM) using a 10 g monofilament, cotton wool, pinprick and a 128 Hz tuning fork after completion of a University of Texas subjective peripheral neuropathy verbal questionnaire.Results. Vibration sense was abnormal in either foot in 8% of subjects. Neuropathy as defined by monofilament, cotton wool and pinprick was present in 26%, 3% and 6% of patients respectively. The respective kappa values (κ) for the comparison between monofilament neuropathy and cotton wool neuropathy, pinprick neuropathy and symptomdefined neuropathy were 0.18, 0.21 and 0.06. The κ-value comparing monofilament and tuning fork-defined neuropathy was 0.24. There was fair agreement between 10 versus 3 sites (κ= 0.60).Conclusion. More abnormalities were detected using the monofilament compared with cotton wool or pinprick. There was poor concordance between symptoms and clinically detected neuropathy. The ideal number of sites that need to be evaluated is still contentious

Barrier Height Variation in Ni-Based AlGaN/GaN Schottky Diodes

In this paper, we have investigated Ni-based AlGaN/GaN Schottky diodes comprising capping layers with silicon-Technology-compatible metals such as TiN, TiW, TiWN, and combinations thereof. The observed change in Schottky barrier height of a Ni and Ni/TiW/TiWN/TiW contact can be explained by stress effects induced by the TiW/TiWN/TiW capping layer, rather than by chemical reactions at the metal-semiconductor interface. Secondary-ion mass spectroscopy and transmission electron microscopy techniques, for samples with and without a TiW/TiWN/TiW cap, have been used to show that no chemical reactions take place. In addition, electrical characterization of dedicated samples revealed that the barrier height of Ni/TiW/TiWN/TiW contacts increases after stepwise selective removal of the TiW/TiWN/TiW cap, thus demonstrating the impact of strain