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An appraisal of the one-flux method for treating carrier transport in modern semiconductor devices

Publication Type:

Journal Article


Solid-State Electron. (UK), Volume 39, Number 6, p.827 - 32 (1996)



bipolar transistors;Boltzmann equation;boundary-value problems;carrier lifetime;carrier mobility;semiconductor device models;


McKelvey's one-flux method, which has been used to investigate transport in short-base bipolar transistors and to specify the carrier mobility in a forward-biased barrier, is put into perspective by a comparison with the usual continuity and drift-diffusion equations. For a bulk semiconductor region in which a small electric field is present, and under typical operating conditions, it is shown that the use of the time-dependent flux method is equivalent to solving the usual continuity and drift-diffusion equations under low-level injection. It is then shown that recent one-flux analyses of short-base transport, for both dc and ac conditions, are equivalent to solving the continuity and drift-diffusion equations with appropriate boundary conditions. It is pointed out that the use of the flux method to resolve the long-standing issue of specifying the carrier mobility within a forward-biased barrier is impeded by a lack of knowledge of the required backscattering coefficients. Recent suggestions for these backscattering coefficients are carefully examined; the physical basis for the choices made, and hence the resulting values of mobility and diffusivity, are questioned


one-flux method;carrier transport;semiconductor devices;short-base bipolar transistors;carrier mobility;forward-biased barrier;continuity equation;drift-diffusion equations;low-level injection;short-base transport;dc conditions;ac conditions;boundary conditions;backscattering coefficients;diffusivity;numerical analysis;