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

Threshold voltage standard deviation (
\sigma V_{th}
) for MESFET's on a liquid encapsulated Czochralski (LEC) grown GaAs wafer was investigated, in connection with dislocation distribution. Threshold voltage (V
th
) 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
\sigma V_{th}
region, strongly networked dislocation cell structure was observed. In the area where dislocations distributed randomly without network structure,
\sigma V_{th}
was small in spite of high dislocation density. For FET's located in the dislocation-free region inside the network cell, low drain current I
ds
and high V
th
were recognized directly by a curve tracer. The experimental results regarding the dislocation network effect on V
th
scattering are discussed along with cathodoluminescence study results.