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

This letter compares the influence of stressed-SiO
2
and Si
3
N
4
films on threshold voltage of WSi
x
-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 SiO
2
film is in compressive stress and Si
3
n
4
film in tensile stress on GaAs.