Browsing by Author "Lee, Wei-Han"

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Error-Free Matthiessen's Rule in the MOSFET Universal Mobility Region
(2013-02-01)
Chen, Ming-Jer
;
Lee, Wei-Han
;
Huang, Yi-Hui
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Through the experimentally validated inversion-layer mobility simulation, we devise an error-free version of Matthiessen's rule for a single-gate n-channel bulk MOSFET in the universal mobility region. The core of the new rule lies in a semi-empirical model, which explicitly expresses the errors due to the conventional use of Matthiessen's rule as a function of both the lowest subband population and the relative strength of individual mobility components. The model holds under practical conditions (with temperatures up to 400 K) and in a broad range of substrate doping concentrations (10(14) to 10(18) cm(-3)). To make the error-free proposal more general, we elaborate on several issues, including strain, impurity Coulomb scattering, and remote scattering. The thin-film case can be treated accordingly.
Evidence for the Fourfold-Valley Confinement Electron Piezo-Effective-Mass Coefficient in Inversion Layers of < 110 > Uniaxial-Tensile-Strained (001) nMOSFETs
(2012-06-01)
Chen, Ming-Jer
;
Lee, Wei-Han
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
We have recently experimentally extracted the piezo-effective-mass coefficients of 2-D electrons via the gate tunneling current of (001) n-channel metal-oxide-semiconductor field-effect transistors under < 110 > uniaxial compressive stress. The results pointed to the existence of a piezo-effective-mass coefficient around the fourfold conduction-band valley in the out-of-plane (quantum confinement) direction. To strengthen this further, here, we provide extra evidence. First, explicit guidelines are drawn to distinguish all the piezo-effective-mass coefficients. Then, a self-consistent strain quantum simulation is executed to fit literature data of both the mobility enhancement and gate current suppression in the uniaxial tensile stress situation. It is found that neglecting the fourfold-valley out-of-plane piezo-effective-mass coefficient, as in existing band structure calculations, only leads to a poor fitting.
Gate Direct Tunneling Current in Uniaxially Compressive Strained nMOSFETs: A Sensitive Measure of Electron Piezo Effective Mass
(2011-01-01)
Lee, Wei-Han
;
Chen, Ming-Jer
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Currently, both the band-structure calculation and the mobility measurement are used to assess the electron piezo-effective-mass coefficients in strained nMOSFETs. In this paper, we present a new experimental method through a fitting of the strain-altered electron gate direct tunneling current. The core of this method lies in the sensitivity of the direct tunneling to the position of the subband level in the presence of the electron piezo-effective-mass coefficients. First, a correction-coefficient generating expression is systematically constructed to compensate for the error in the subband levels due to the use of a triangular potential approximation. Then, with the known deformation potential constants and uniaxially compressive stress in the channel as inputs, a strain quantum simulator is carried out. The resulting gate direct tunneling current is used to fit experimental data, thus leading to the values of the piezo-effective-mass coefficients associated with the twofold and fourfold valleys. The comparison of the extracted piezo-effective-mass coefficients to those published in the literature is made.
Temperature-Dependent Remote-Coulomb-Limited Electron Mobility in n(+)-Polysilicon Ultrathin Gate Oxide nMOSFETs
(2011-04-01)
Chen, Ming-Jer
;
Chang, Sou-Chi
;
Kuang, Shin-Jiun
;
Lee, Chien-Chih
;
Lee, Wei-Han
Additional electron mobility due to remote scatterers in n(+)-polysilicon 1.65-nm gate oxide (SiO(2)) n-channel metal-oxide-semiconductor field-effect transistors is experimentally extracted at three different temperatures (i.e., 233, 263, and 298 K). The core of the extraction process consists of simulated temperature-dependent universal mobility curves and Matthiessen's rule in a mobility universality region. Resulting additional mobility for the first time experimentally exhibits a negative temperature coefficient, confirming interface plasmons in a polysilicon depletion region to be dominant remote Coulomb scatterers. We also present corroborative evidence as quoted in the literature, including: 1) calculated temperature-dependent remote Coulomb mobility due to ionized impurity atoms in a polysilicon depletion region; 2) experimentally assessed additional mobility at room temperature; and 3) simulated remote Coulomb mobility due to interface plasmons in a polysilicon depletion region as well as its temperature coefficient. Validity of Matthiessen's rule used in this paper is verified.