Monte Carlo Based Calculation of Transport Parameters for Wide Band Gap Device Simulation
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MONTE CARLO BASED CALCULATION OF TRANSPORT PARAMETERS FOR WIDE BAND GAP DEVICE SIMULATION E. Bellotti *, M. Farahmand *, H.-E Nilsson #, K. F. Brennan * and P. P. Ruden ** *
School of ECE, Georgia Tech, Atlanta, GA 30332, [email protected] # Department of Information Technology, Mid-Sweden University, Sundsvall, Sweden ** Dept. of ECE, University of Minnesota, Minneapolis, MN 55455
ABSTRACT We present Monte Carlo based calculations of transport parameters useful in the simulation of III-nitride and SiC based devices. The calculations are performed using a full band ensemble Monte Carlo model that includes numerical formulations of the phonon scattering rates and impact ionization transition rates. Calculations are made for the wurtzite and zincblende phases of GaN, the wurtzite phase of InN, and the 3C (cubic) and 4H phases of SiC. The basic transport parameters determined are saturation drift velocity, and the ionization coefficients as a function of applied electric field. Results from the various materials are finally compared.
INTRODUCTION Wide band-gap semiconductors are becoming of increasing importance in many emerging optoelectronic and electronic device applications. Among these applications are ultraviolet (UV) photodetectors, blue and UV light emitters, and high frequency, high power electronic devices. Of the emerging wide band-gap semiconductors, the most promising candidates for power field effect transistors, FETs, are SiC and the III-nitrides. It is well known that SiC or GaN based transistors offer significantly higher maximum output power than comparable structures made from GaAs or Si [1,2]. Owing to their relatively wide and direct energy band-gap, the III-nitride semiconductors are in addition particularly useful for UV and blue-light photonic detectors and emitters. The III-nitrides offer an additional advantage since heterostructures can be made from these materials. Along with GaN, the InN ternary alloy, InGaN, has found application in a variety of heterostructure based opto-electronic devices. The purpose of this paper is to present a review of the calculated transport parameters for GaN, InN, and the cubic and 4H phases of SiC. MODEL DESCRIPTION Within the framework of the materials theory based modeling methodology [3] the first step in studying the transport parameters of semiconductor materials is the calculation of the electronic structure. The band structures of a number of wide band gap material systems, used within the Monte Carlo simulation are calculated using the empirical pseudopotential method. Though ab initio methods have been applied to the study of the band structures of the wide gap semiconductors [4], the empirical T6.24.1
pseudopotential method is employed herein since it offers a computationally efficient and reasonably accurate accounting of the band structure. The band structures of several wide gap materials are computed for a suitable number of k-points within the irreducible wedge taking into account the symmetry of the different crystalline structures. V
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