Structures for high electron mobility transistor and depletion-mode transistor

A depletion-mode high-electron-mobility-transistor structure, comprising;

• a composite semiconductor layer formed on a substrate, constructed to provide a conductive channel with a two-dimensional electron gas;
• a first electrode formed on the composite semiconductor layer and electrically connected to the conductive channel;
• a second electrode formed on the composite semiconductor layer, electrically connected to the conductive channel, and spaced apart from the first electrode in a first direction;
• semiconductor isles, formed directly on the composite semiconductor layer and spaced apart from each other in a second direction perpendicular to the first direction;
• a gate electrode, formed above the semiconductor isles to contact with the semiconductor isles via at least two contact holes;
• and
• a conductive plate formed between the contact holes in view of the second direction, wherein the conductive plate does not physically contact the composite semiconductor layer;
• wherein when an external bias voltage is absent a portion of the two-dimensional electron gas under the semiconductor isles is depleted and another portion of the two-dimensional electron gas under the conductive plate electrically connects the first and second electrodes.