Thin film transistor for imaging system

An annular thin film transistor comprising:

• a layer of a semiconductor material;
• 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.

A serpentine thin film transistor comprising:

• a layer of a semiconductor material;
• 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.