@inproceedings { 6599855, title = {Application of the traditional compact expressions for estimating the regional signal-delay times of heterojunction bipolar transistors}, journal = {J. Vac. Sci. Technol. A, Vac. Surf. Films (USA)}, volume = {18}, number = {2}, year = {2000}, note = {HBT;compact expressions;regional signal-delay times;heterojunction bipolar transistors;numerical device simulation;regional partitioning;phenomenological scheme;stored free charge;space-charge region;quasineutral emitter;effective collection velocity;band-gap narrowing;quasiballistic transport;hot-electron injection;}, pages = {775 - 9}, type = {inproceedings}, address = {Ottawa, Ont., Canada}, abstract = {The applicability of the traditional compact expressions for estimating the regional signal-delay times of heterojunction bipolar transistors is examined by means of a comparison with numerical device simulation. Regional partitioning in the numerical simulations is achieved by means of a simple phenomenological scheme. It is shown that the traditional expression for the emitter delay is inadequate due to a neglect of both the stored free charge within the emitter-base, space-charge region, and the stored charge in the quasi-neutral emitter. The importance of properly choosing the effective collection velocity when estimating the base delay is demonstrated by considering the effects of band-gap narrowing, quasi-ballistic transport, and hot-electron injection. It is pointed out that the effects of finite charge in the collector-base, space-charge region cannot be neglected when computing the collector delay}, keywords = {heterojunction bipolar transistors;hot carriers;numerical analysis;semiconductor device models;}, URL = {http://dx.doi.org/10.1116/1.582178}, author = { Pulfrey, D.L. and Fathpour, S. and Denis, A.S. and Vaidyanathan, M.A. and Hagley, W.A. and Surridge, R.K.} }