V. Madangarli

Design rules for field plate edge termination in SiC Schottky diodes

Practical design of silicon carbide (SiC) Schottky diodes incorporating a field plate necessitates an understanding of how the addition of the field plate affects the performance parameters and the relationship between the diode structure and diode performance. In this paper, design rules are presented for SiC Schottky diodes that incorporate field plate edge termination. The use of an appropriate field plate edge termination can improve the reverse breakdown voltage of a SiC Schottky diode by a factor of two. Reverse breakdown voltage values can be obtained that are up to 88% of the theoretical maximums.

The influence of the semiconductor and dielectric properties on surface flashover in silicon-dielectric systems

New experimental results on surface flashover are reported for high field silicon-dielectric systems. Different conditions of the lateral surface, contacts and ambient dielectrics have been studied. The strong influence of the semiconductor quality, and that of the dielectric properties, on the prebreakdown and breakdown response of the system, is demonstrated. All experimental results strongly support the conclusion that surface flashover in silicon systems is a physical process totally different from semiconductor surface breakdown. This conclusion has important practical application in the improvement of the performance of photoconductive power switches, severely limited by premature breakdown effects. >

SiC planar MOS-Schottky diode: a high voltage Schottky diode with low leakage current

Abstract A new diode structure, called planar MOS-Schottky Diode (MOSSD), is proposed to reduce the reverse leakage current in SiC Schottky diode. The reverse leakage current has been reduced by one order of magnitude by using the MOSSD structure while the reverse breakdown characteristic is improved from soft breakdown to abrupt breakdown. Further, measurements on MOSSDs with thick and thin oxide MOS regions indicate that the forward current through a MOSSD with a thin oxide can be up to 90% that through a conventional Schottky diode without buried MOS structures. From high temperature measurements it is evident that the reverse characteristics of MOSSDs have less temperature dependence compared to pure Schottky diodes.

Surface flashover in silicon-vacuum systems

The properties of the prebreakdown response of silicon-vacuum systems under HV excitation are presented. The most frequent case of system breakdown by surface flashover is treated. The particular properties of the system response in the high-field pulsed regime demonstrate the essential differences between the silicon-vacuum and solid-insulator-vacuum systems. The main ideas of a new physical model of surface flashover in silicon-vacuum systems are presented. The properties of the surface flashover response are discussed in terms of the proposed model. A concept called system surface flashover sensitivity is introduced to provide a better understanding of the surface flashover physical process in silicon-vacuum systems. >

On the negative differential resistance effect in high‐field semiconductor‐dielectric systems

The active role of the dielectric in high‐field semiconductor‐dielectric systems (HFSDS) and the experimental results concerning partial and total surface flashover in HFSDS are presented. The system negative differential resistance effect by partial surface flashover is explained on the basis of a two‐channel model with an appropriate equivalent circuit correlated with the potential distribution along the semiconductor.

Current–voltage characteristics of an integrated Schottky diode

Abstract It is possible to reduce the reverse leakage current of a Schottky diode relative to its forward current through careful design of the Schottky electrode. This paper examines the J – V characteristics of a Schottky diode that employs a compound Schottky electrode. The compound electrode design presented in this paper increases the reverse breakdown voltage and reduces the reverse leakage current.

The Response of High Voltage 4H-SiC P-N Junction Diodes to Different Edge Termination Techniques

Edge termination is an important aspect in the design of high power p-n junction devices. In this paper, we compare the breakdown characteristics of 4H-SiC p + -n diodes with oxide passivation and with edge termination using either low or high energy ion implantations. N- and p-type epilayers of 4H-SiC were grown by chemical vapor deposition on n + 4H-SiC wafers. Circular mesa structures of different diameters were patterned and isolated by reactive ion etching. Four types of samples were fabricated. The first group was not implanted or passivated and was left for control. The second type consisted of oxide-passivated diode structures while the third and fourth types were ion implanted with 30 keV Ar + and 2.2 MeV He + ions, respectively. The time dependent breakdown characteristics were determined using a fast voltage ramp technique. The reverse bias breakdown voltages and leakage currents of these diodes were different for the different types of the edge termination. Diodes terminated using 2.2 MeV ion implantation yielded the best breakdown characteristics. A majority of the diodes exhibited abrupt breakdown.

New results on surface flashover in silicon-dielectric systems

New experimental results are reported for silicon samples at high fields in different ambients: vacuum, N2, air, SF6 and SF6 + N2 mixtures, for different experimental conditions. The strong influence of the semiconductor quality and ambient dielectric on the prebreakdown and breakdown response of the system is presented. The high surface flashover sensitivity of semiconductor-vacuum system, as well as the significant interface activity in air and N2 is explained. Using a new physical model of the breakdown in semiconductor- dielectric systems, a new technique was developed consisting of an in-situ treatment of the semiconductor sample (in vacuum) before performing the high field measurements in SF6. Dramatic improvement of the voltage hold-off was obtained in one atmosphere (absolute) SF6. All standard good quality samples, subjected to the vacuum pre-treatment, supported without surface flashover, high fields in the range of 75 - 85 kV/cm, close to the critical breakdown field for SF6 gas at one atmosphere (approximately 89 kV/cm). The role of different defects in producing premature breakdown by surface flashover in SF6 is discussed.

SiC Epitaxial Growth on Carbon

The possibility of single crystal SiC expitaxial growth on freestanding amorphous carbon films (500–1000 A) as well as thin amorphous carbon layers deposited on mono-crystalline SiC seeds, by conventional physical vapor transport (PVT) technique, is demonstrated. Preliminary experiments indicate that under certain specific growth conditions, 3D SiC single crystals (100 – 600 A) of different polytypes can be grown on freestanding amorphous carbon layers, with more or less equal probability of formation for each polytype. On the other hand, under low axial temperature gradients (

Influence Of Electrode Geometry On The High-field Characteristics Of Photoconductive Silicon Wafers

A series of experiment were conducted to study the influence of electrode geometry on the prebreakdown (and breakdown) characteristics of high resistivity ({rho} > 30 k{Omega}-cm), p-type Si wafers under quasi-uniform and non-uniform electric field configurations. In the quasi-uniform field configuration, the 1mm thick Si wafer was mounted between the slots of two plane parallel stainless steel disc electrodes (parallel), while the non-uniform field was obtained by mounting the wafer between two pillar-type electrodes with a hemispherical tip (pillar). The main objective of the above investigation was to verify if the uniform field configuration under a parallel system has a positive influence by reducing the field enhancement at the contact region, as opposed to the definite field enhancement present in the case of the non-uniform pillar system. Also, it was proposed to study the effect of the contact profile on the field distribution over the wafer surface and hence its influence on the high-field performance of the Si wafers.