%0 Conference Paper %B J. Vac. Sci. Technol. A, Vac. Surf. Films (USA) %D 2000 %T Application of the traditional compact expressions for estimating the regional signal-delay times of heterojunction bipolar transistors %A Pulfrey, D L %A Fathpour, S %A Denis, A S %A Vaidyanathan, M A %A Hagley, W A %A Surridge, R K %C Ottawa, Ont., Canada %K heterojunction bipolar transistors;hot carriers;numerical analysis;semiconductor device models; %P 775 - 9 %U http://dx.doi.org/10.1116/1.582178 %V 18 %X 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 %Z 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; %9 inproceedings