P. Taylor

Numerical Parameterization of Chemical-Vapor-Deposited (CVD) Single-Crystal Diamond for Device Simulation and Analysis

High-quality electronic-grade intrinsic chemical- vapor-deposited (CVD) single-crystal diamond layers having exceptionally high carrier mobilities have been reported by Isberg et al. This makes the realization of novel electronic devices in diamond, particularly for high-voltage and high-temperature applications, a viable proposition. As such, material models which can capture the particular features of diamond as a semiconductor are required to analyze, optimize, and quantitatively design new devices. For example, the incomplete ionization of boron in diamond and the transition to metallic conduction in heavily boron-doped layers require accurate carrier freeze-out models to be included in the simulation of diamond devices. Models describing these phenomena are proposed in this paper and include numerical approximation of intrinsic diamond which is necessary to formulate doping- and temperature-dependent mobility models. They enable a concise numerical description of single-crystal diamond which agrees with data obtained from material characterization. The models are verified by application to new Schottky m-i-p+ diode structures in diamond. Simulated forward characteristics show excellent correlation with experimental measurements. In spite of the lack of impact ionization data for single-crystal diamond, approximation of avalanche coefficient parameters from other wide-bandgap semiconductors has also enabled the reverse blocking characteristics of diamond diodes to be simulated. Acceptable agreement with breakdown voltage from experimental devices made with presently available single-crystal CVD diamond is obtained.

Ultra-high voltage device termination using the 3D RESURF (super-junction) concept - experimental demonstration at 6.5 kV

We propose here and experimentally demonstrate a novel breakdown termination termed The 3D-RESURF Termination that can be applied to a large class of high to ultra-high voltage devices, such as diodes, thyristors, IGBTs, etc. The novel termination is based on the 3D RESURF concept (lateral super-junction) proposed by us and others for lateral integrable devices. We have fabricated vertical diodes and IGBTs rated at 6.5 kV and demonstrated that the use of 3D RESURF p and n layers placed between adjacent p+ floating rings resulted in maximum breakdown voltage (6.5 kV). This is 2.5 kV larger than the breakdown voltage obtained from a standard field ring terminated device fabricated side by side on the same chip. Moreover, the 3D-RESURF edge termination uses a total length of 1 mm, which is only 60% of standard 6.5 kV JTE terminations. This results in area saving of up to 40%, depending on the active area of the chip.

Termination Structures for Diamond Schottky Barrier Diodes

A comprehensive study on the off-state performance of synthetic single crystal (SSC) diamond Schottky barrier diodes (SBDs) is the subject of this paper. Three termination structures suitable for unipolar diamond power devices are numerically investigated. Comparisons between the three terminations, based on blocking performance and area consumption are presented. Optimum design parameters derived from simulations are included for each structure. Experimental results of reverse-biased diamond SBDs for the first time with ramp angle termination are also presented

Single crystal diamond M-i-P diodes for power electronics

Its outstanding electronic properties and the recent advances in growing single-crystal chemically vapour-deposited substrates have made diamond a candidate for high-power applications. Diamond Schottky diodes have the potential of being an alternative to silicon p-i-n and SiC Schottky diodes in power electronic circuits. Extensive experimental and theoretical results, for both on- and off-state behaviour of metal-insulator-p-type diamond Schottky structures, are presented here. The temperature dependence of the forward characteristics and electrical performance of a termination structure suitable for unipolar diamond devices are also presented.

Suppression of parasitic JFET effect in trench IGBTs by using a self-aligned p base process

Abstract This paper presents the suppression of the parasitic JFET effect in high voltage Trench insulated gate bipolar transistors (IGBTs) by employing a new self-aligned p base process. The parasitic JFET effect is no longer negligible because the lowly doped n− drift region becomes longer and at the same time the cell current density becomes lower in high voltage applications. The self-aligned p base process is based on the use of a common nitride mask for trench etching and p boron diffusion and therefore eliminates an extra process mask. Furthermore, the self-aligned p base structure effectively suppresses the parasitic JFET effect into a small area near the trench source and results in considerably enhanced on-state performance. Extensive numerical simulations using the MEDICI simulator have been carried out and the results show that by using the new self-aligned p base process one can relieve the pressure resulted from processing very deep trenches in high voltage Trench IGBTs.

Numerical and Experimental Analysis of Single Crystal Diamond Schottky Barrier Diodes

We present our findings on the numerical and experimental analysis of diamond Schottky Barrier diodes (SBDs) comprising of intrinsic single crystal (SC) chemical vapour deposited (CVD) diamond layers grown on highly boron doped substrates also grown by CVD. Good correlation with experimental results has been achieved through numerical modelling that has incorporated previously reported data on transport physics and carrier activation. With our numerical model, we are able to match to within 12 to 15% of the measured forward characteristics of fabricated diamond SBDs up to 2 V in excess of the turn on voltage, for two different Schottky metals.

Highly efficient edge terminations for diamond schottky diodes

Two termination structures suitable for diamond Schottky diodes are presented in this paper. A thorough comparison between the two structures, concerning both electrical and geometrical aspects, is included. The study is based on theoretical models and extensive numerical results. High termination efficiencies, up to 93%, are reported

Enhanced on-state performance trench IGBT with a self-aligned p base

This paper presents an enhanced on-state performance of a 3.3 kV Trench IGBT with a self-aligned p base. The self-aligned p base process is based on the use of a common nitride mask for trench etching and p base boron implantation and diffusion which eliminates an extra process mask. Furthermore, the self-aligned p base structure virtually suppresses the parasitic JFET effect present in high-voltage trench IGBTs and results in considerably enhanced on-state performance. Extensive numerical simulations using the MEDICI simulator have been carried out and the results show that by adopting self aligned p base process one can relieve the pressure resulted from processing very deep trenches in high-voltage trench IGBTs.

High voltage Schottky barrier diodes in synthetic single crystal diamond

Recent results proved the possibility of obtaining synthetic single crystal diamond with good crystal quality and excellent consistency. High voltage p-type Schottky barrier diodes (SBDs) have been fabricated on diamond, using gold (Au) as the Schottky metal and boron as doping material. In this study, on-state and off-state experimental and simulated data are presented and excellent theory-experiment agreement is revealed. The usage of diamond SBDs as ultra violet (UV) photodetectors is also analysed. On-state and off-state simulations, for different optical beam power densities, have been carried out and the theoretical data are provided.

A new single gate MOS controlled thyristor with current saturation and large SOA

A novel single gate MOS controlled current saturation thyristor (MCST) device is proposed. In the on-state the MCST operates in thyristor-like mode at low anode voltage and enters the IGBT-like mode automatically with increasing anode voltage, offering a low on-state voltage drop and current saturation capability. The saturation current density of the MCST is strongly dependent on the on-set voltage or the p+ buffer/n-well junction, leading to its excellent safe operation area (SOA) and making it suitable for high power applications.