Browsing by Author "Sano, Nobuyuki"

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Monte Carlo simulation of random dopant fluctuation in C-V characteristics using image charge model and adequately determined length scale
(2019-09-01)
Chih-Wei, Yao
;
Sano, Nobuyuki
;
Watanabe, Hiroshi
;
電機工程學系
;
電信工程研究所
In recent years, it has been under discussion how the distribution of discrete dopant ions affects the performance of electron devices. In particular, dopant ions near the interface may not be surrounded by a sufficient number of carriers to achieve full screening. In addition, the screening effect is modeled assuming equilibrium, which cannot be validated. Therefore, the device modeling of the screening effect must be refined to cover the entire range of applied voltages. In the present work, we adequately define the length scale covering the entire voltage region in the capacitancevoltage (C-V) characteristics. Furthermore, we propose an image charge model for residual long-range potential of dopant ions near the interface. The Monte Carlo simulation of random dopant fluctuation in the C-V characteristics of 100 samples of MOS capacitors demonstrates that the main contributor to random dopant fluctuation is the location fluctuation of discrete dopant ions. (C) 2019 The Japan Society of Applied Physics.
Physics of Discrete Impurities under the Framework of Device Simulations for Nanostructure Devices
(2018-12-01)
Sano, Nobuyuki
;
Yoshida, Katsuhisa
;
Yao, Chih-Wei
;
Watanabe, Hiroshi
;
電機工程學系
Localized impurities doped in the semiconductor substrate of nanostructure devices play an essential role in understanding and resolving transport and variability issues in device characteristics. Modeling discrete impurities under the framework of device simulations is, therefore, an urgent need for reliable prediction of device performance via device simulations. In the present paper, we discuss the details of the physics associated with localized impurities in nanostructure devices, which are inherent, yet nontrivial, to any device simulation schemes: The physical interpretation and the role of electrostatic Coulomb potential in device simulations are clarified. We then show that a naive introduction of localized impurities into the Poisson equation leads to a logical inconsistency within the framework of the drift-diffusion simulations. We describe a systematic methodology for how to treat the Coulomb potential consistently with both the Poisson and current-continuity (transport) equations. The methodology is extended to the case of nanostructure devices so that the effects of the interface between different materials are taken into account.