Thin film transistor for imaging system

An annular thin film transistor includes an annular source electrode disposed above the layer of the semiconductor material, a drain electrode disposed above the layer of the semiconductor material within the annular source electrode, and an active channel between the drain electrode and the annular source electrode, wherein a surface of the active channel comprises exposed semiconductor material. Further, a serpentine thin film transistor includes a serpentine source electrode disposed above the layer of the semiconductor material, a drain electrode disposed above the layer of semiconductor material and substantially within a recess formed by the serpentine source electrode, wherein the drain electrode is configured to substantially conform to the recess, and an active channel between the drain electrode and the serpentine source electrode, wherein the active channel has a substantially consistent length, and wherein a surface of the active channel comprises exposed semiconductor material.