Disclosed semiconductor structures include a stack of III-V semiconductor layers and a III-V semiconductor device and a silicon device on the stack. The III-V semiconductor device includes, among other components, a barrier layer above and immediately adjacent to a III-V semiconductor surface at the top of the stack in a first area. The silicon device includes, among other components, a silicon-based layer above and immediately adjacent to the same III-V semiconductor surface at the top of the stack in a second area. Thus, the barrier layer and the silicon-based layer are at the same level above the substrate. Optionally, an isolation well can be within the stack adjacent to the III-V semiconductor surface in the second area (e.g., to electrically isolate the III-V semiconductor device from the silicon device). Also disclosed are methods of forming the semiconductor structures.

A transition metal dichalcogenide (TMD) transistor includes a substrate, an n-type two-dimensional (2D) TMD layer, a metal source electrode, a metal drain electrode, and a gate dielectric. The substrate has a top portion that is an insulating layer, and the n-type 2D TMD layer is on the insulating layer. The metal source electrode, the metal drain electrode, and the gate dielectric are on the n-type 2D TMD layer. The metal gate electrode is on top of the gate dielectric and is between the metal source electrode and the metal drain electrode.