Space-charge-limited solid-state devices

The history and development of interest in space-charge-limited (scl) current in solids is traced from early work on the electron atmosphere in insulators to present understanding of the physical mechanisms of current and awareness of device potentialities. SCL solid-state devices have achieved practical realization through the use of single crystals and evaporated layers of cadmium sulphide, but high-resistivity single crystal silicon is likely to be a preferred material for practical and reliable devices. The square-law dielectric diode is the fundamental scl solid-state device, and theoretical studies and experimental investigations of this device are described. The design and operation of the dielectric triode with negative and positive gate bias are discussed, the input resistance of this device is high; it is insensitive to changes of temperature, and its operating characteristics and parameters are described well by the concepts of perveance and amplification factor. It is now apparent that there is considerable scope in future electronics for scl solid-state devices as individual elements and in thin-film integrated circuits.