Ferenc Masszi

Lifetime in proton irradiated silicon

Deep energy levels caused by high‐energy low‐dose proton irradiation of both n‐ and p‐type silicon have been investigated. Energy positions in the band gap, capture coefficients, and their temperature dependences for majority and minority carrier capture and entropy factors have been measured by deep level transient spectroscopy. Computer simulations have been employed to obtain the correct numbers of injected charge carriers needed for the evaluation of minority carrier capture data. From these measurements, it is possible to deduce the charge carrier lifetime profiles in proton irradiated n‐type silicon for different injection concentrations and temperatures. At room temperature and for low injection, it is found that the singly negative divacancy level with a band‐gap enthalpy of HC−HT=0.421 eV has the largest influence on the lifetime. At high injection, the vacancy–oxygen center, HC−HT=0.164 eV, is mostly responsible for the lifetime reduction.

Complementary Si MESFET concept using silicon-on-sapphire technology

Complementary Si MESFETs (CMES) for integrated circuits using silicon-on-sapphire are described. Not only the gate, but also the source and drain of the n-transistors and p-transistors are Schottky junctions, using very high barrier heights for the gate and low barrier heights for source and drain. Only two Schottky metals are used: one, Ir or Pt, giving a high barrier on nSi, and hence low on pSi; the other, Er or Tb, showing the opposite behavior. The basic differences between MES and MOS are pointed out and design criteria for CMES inverters using normally-off type transistors are given.<<ETX>>

Computer simulations of Schottky contacts with a non-constant recombination velocity

Abstract The problem of modeling Schottky contacts for computer-aided physical simulation is investigated. Boundary conditions using a current dependent carrier recombination velocity distribution are developed, and installed in the two-dimensional simulation program BAMBI.

Computer modeling and comparison of different rectifier (M-S, M-S-M, p-n-n + ) diodes

A computer method is used to investigate the forward characteristics of high-barrier Schottky diodes with different back contacts. A discussion of rectifier-parameter optimization is presented, together with comparisons of different diode types, including p-n-n+diodes. The superiority, in certain voltage ranges, of the high-barrier Schottky diodes over p-n-n+diodes is demonstrated.

A Comparison Between the Diffusion Model and the Combined Diffusion-Thermionic-Emission Model for MS-Junctions by Two-Carrier Numerical Computations

The diffusion model and the combined thermionic-emission-diffusion model for metal-semiconductor junctions have been used in combination with a modified Gummel-De Mari algorithm to obtain one-dimensional, numerical two-carrier solutions, for silicon Schottky diode structures. Solutions for some diode functions vs. voltage, current density, generation-recombination current injection ratio, minority carrier injection ratio, stored charge, and differential capacitance were obtained. For some applied voltages some diode functions vs. positions were calculated: the band diagram including the quasi-Fermi levels, electron and hole carrier density, the total hole current density, the hole drift current density, the electron drift current density and the net charge density. The parameters that have been varied are the barrier height, the carrier life-times, the doping concentration and the length of the diode structure. The results have been compared to and correlate with previous investigations by Vaitkus and Green & Shewchun. A comparison between the diffusion and the combined diffusion-thermionic emission model have been done. Standard methods for determining structure parameters as the 1n I vs. V plot, the Norde plot and the 1/C2 vs. V plot have been applied to the numerical results. From this plot the ideality factor, series resistance, barrier height, doping concentration have been determined and the results have been compared to the originally given parameters. The various models result in significant differences (a) on barrier height dependence of injected minority carrier current density, and (b) on the differential resistance at zero bias voltage. The results have also been compared with fabricated silicide and silicon Schottky diodes.

A Lateral Bipolar Transistor Concept on SOI using a Self-Aligned Base Definition Technique

A lateral bipolar transistor technology for the fabrication of high performance lateral devices on SOI is presented. The presented technology makes use of selective etching procedures and time controlled wet etching to define the basewidth of the devices. 2-D process simulation results are presented together with 2-D device simulations showing the applicability of the proposed process.

Examination of MOS structures by a 3D particle dynamics Monte-Carlo simulator including electrothermal effects

The MicroMOS quasi-deterministic particle dynamics 3D Monte-Carlo program for submicron MOS transistors is now extended with electronphonon interaction models for intervalley scattering and with a carrier-lattice energy exchange model. The impact ionisation and Auger recombination models are also improved. The carrier transport and lattice heat transport problems are self-consistently solved. As example the results of simulation, the spatial distribution of electrons, electron-phonon scattering events, impact ionisation events, Auger recombination events and the lattice temperature are presented. A new, low drain-to-source voltage breakdown effect has been observed.

Investigation of Silicon Carbide Diode Structures via Numerical Simulations Including Anisotropic Effects

The Poisson’s and continuity equations based SiC-DYNAMIT-1DT/2DT simulators with anisotropic material analysis capabilities were developed. A comparison of experimental and simulated forward I/V curves for three 6H-SiC P+NN+ diodes is presented and the related model parameter adjustment problems are discussed. The influence of the strong electron mobility anisotropy on carrier distributions is investigated and the existence of a “mobility anisotropy induced anomalous charge accumulation effect” is demonstrated.

The effect of using different transport models in computer simulations of the permeable-base transistor

The PBT is a short channel device and hot electron effects are expected to be important and the transport model used in the simulation is critical. The present work compares the effect of different transport models on the operation of a submicron PBT. The transport model used are the ordinary drift-diffusion model and the hydrodynamicc models as they are implemented in MEDICI Ver. 1.1. In submicron devices the transport parameters become both device and bias dependent. The transport parameters are directly related to the distribution function and should be extracted from the solution of Boltzmanns Transport Equation (BTE). The most popular and effective way of solving the BTE is Monte Carlo simulation. In this work we have extracted transport parameters from Monte Carlo simulation using one dimensional boundary for particles and a fixed electric field extracted from two-dimensional simulation in MEDICI. The Monte Carlo simulation, parameter extraction and MEDICI simulation have been repeated until the change in electric field between iterations could be neglected. Both I-V and fT results have been analysed. It is clear that the hydrodynamic model gives higher current levels and higher fT than the drift-diffusion model.

A theoretically accurate mobility model for semiconductor device drift-diffusion simulation

A novel semiconductor charge carrier mobility model obtained by Kohlers variational method for Boltzmann transport equation solution is presented. Acoustic phonon scattering, ionized impurity scattering, and carrier-carrier scattering are taken into account. Majority electron and hole mobilities in n- and p-type silicon versus impurity and carrier concentration, and temperature are calculated and compared with published experimental data.