Threshold voltage scattering of GaAs MESFET´s fabricated on LEC-grown semi-insulating substrates

Threshold voltage standard deviation ( ) for MESFET\´s on a liquid encapsulated Czochralski (LEC) grown GaAs wafer was investigated, in connection with dislocation distribution. Threshold voltage (Vth) scattering was found to be strongly correlated to the dislocation cell network structure in the substrate. This dislocation cell network is characteristic of the LEC-grown crystal. At large region, strongly networked dislocation cell structure was observed. In the area where dislocations distributed randomly without network structure, was small in spite of high dislocation density. For FET\´s located in the dislocation-free region inside the network cell, low drain current Idsand high Vthwere recognized directly by a curve tracer. The experimental results regarding the dislocation network effect on Vthscattering are discussed along with cathodoluminescence study results.