Comparison of the orientation effect of SiO2- and Si3N4-encapsulated GaAs MESFET´s

This letter compares the influence of stressed-SiO2and Si3N4films on threshold voltage of WSix-gate self-aligned GaAs MESFET´s oriented along [011]- and [011]-directions. The experimental results showed that the orientation effect originates, mainly from piezoelectric effect due to strain in the n-layers, induced by the dielectric overlayer. Furthermore, the disagreement among workers regarding the preferable orientation turned out to be due to the difference of the stress-sign in dielectric overlayers employed; it was confirmed that SiO2film is in compressive stress and Si3n4film in tensile stress on GaAs.