Carrier accumulation and space-charge-limited current flow in field-effect transistors

Abstract

This paper reports an investigation of devices fabricated by lateral diffusion techniques which have non-uniform doping profiles along the channel. The application of a two-dimensional numerical method to a device model representing these devices shows carrier accumulation in the conductive channel. The increase of carrier concentration with the increasing drain-to-source voltages is caused by the interaction of the source and the drain N +-regions. This indicates the possibility of the space-charge-limited current which is a different conduction mechanism from that of the conventional devices. From the study of one-dimensional N +-N-N + structures, the length-to-L DE (extrinsic Debye length) ratio of the channel and the crossover voltage have been recognized as important parameters in realizing the space-charge-limited current. The drain characteristics of a device model with a small crossover voltage and a small length-to-L DE ratio are obtained by a simple analysis. Triode-like characteristics are found for this model as expected. © 1970.