Experimental correlation between substrate properties and GaAs MESFET transconductance

The relationship between the characteristics of FET's obtained by direct ion implantation and the properties of a GaAs semi-insulating substrate was investigated. A positive correlation was observed between the dislocation etch-pit density, the as-grown mobility, the mobility after implantation, and the device transconductance. The observation of dislocations' effect on mobility is consistent with the model that dislocations act as segregation centers for imperfections. Localized substrate inhomogeneties are shown to affect the GaAs FET's frequency performance via the mobility.