An ensemble Monte Carlo simulation has been used to model bulk electron transport at room and higher temperatures as a function of high electric fields. Electronic states within the conduction band valleys at the Γ 1 , U , M , Γ 3 and K are represented by non-parabolic ellipsoidal valleys centred on important symmetry points of the Brillouin zone. The simulation shows that intervalley electron transfer plays a dominant role in GaN in high electric fields leading to a strongly inverted electron distribution and to a large negative differential conductance. Our simulation results have also shown that the electron velocity in GaN is less sensitive to temperature than in other III-V semiconductors like GaAs. So GaN devices are expected to be more tolerant to selfheating and high ambient temperature device modeling. Our steady state velocity-field characteristics are in fair agreement with other recent calculations. Keywords: Ensemble Monte Carlo; ellipsoidal valleys; Brillouin zone; device modeling. 3915 Int. J. Mod. Phys. B 2008.22:3915-3922. Downloaded from www.worldscientific.com by UNIVERSITY OF CALIFORNIA @ SANTA CRUZ on 02/03/15. For personal use only. 3916 A. R. Binesh et al.
Ramsar is one of the highest background radiation areas in the world, whose natural radioactivity is due to (238)U natural series and its decay products, especially (226)Ra and (220)Rn, which have been brought to the surface by water of hot springs. In this study, radon concentration in 14 drinking water sources of the Ramsar region has been measured with the PRASSI system. The results show all of the water supplies have radon concentration greater than 10kBq/m(3) as normal level. Moreover, the estimated mean annual radiation dose to public due to waterborne radon has also been evaluated.
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