A semiconductor device includes a bidirectional GaN FET formed on a non-insulating substrate. The semiconductor device further includes a first electrical clamp connected between the substrate and a first source/drain node of the bidirectional GaN FET, and a second electrical clamp connected between the substrate and a second source/drain node of the bidirectional GaN FET. The first clamp and the second clamp are configured to bias the substrate at a lower voltage level of an applied bias to the first source/drain node and an applied bias to the second source/drain node, within an offset voltage of the relevant clamp.