AN APPRAISAL OF THE ONE-FLUX METHOD FOR TREATING CARRIER TRANSPORT INMODERN SEMICONDUCTOR-DEVICES

McKelvey's one-flux method, which has recently been used to investigat e transport in short-base bipolar transistors and to specify the carri er mobility in a forward-biased barrier, is put into perspective by a comparison with the usual continuity and drift-diffusion equations. Fo r a bulk semiconductor region in which a small electric field is prese nt, and under typical operating conditions, it is shown that the use o f the time-dependent flux method is equivalent to solving the usual co ntinuity and drift-diffusion equations under low-level injection. It i s then shown that recent one-flux analyses of short-base transport, fo r both d.c. and a.c. conditions, are equivalent to solving the continu ity and drift-diffusion equations with appropriate boundary conditions . It is pointed out that the use of the flux method to resolve the lon g-standing issue of specifying the carrier mobility within a forward-b iased barrier is impeded by a lack of knowledge of the required backsc attering coefficients. Recent suggestions for these backscattering coe fficients are carefully examined; the physical basis for the choices m ade, and hence the resulting values of mobility and diffusivity, are q uestioned.