Soft proton isolation process for an acoustic charge transport integrated circuit

A method for electrically isolating an integrated circuit element in an acoustic charge transport device, said method comprising the steps of:

• a) providing a semi-insulating substrate;
• b) providing an epitaxial layer on the semi-insulating substrate with a thickness and carrier concentration appropriate for an ACT device;
• c) providing a circuit element semiconductor layer in the epitaxial layer for construction of an integrated circuit element, the layer having a thickness substantially less than the thickness of the epitaxial layer and having a carrier concentration substantially greater than the ACT epitaxial layer;
• d) laterally isolating the semiconductor layer from other regions of the ACT epitaxial layer;
• and
• e) bombarding the semiconductor layer with protons or deuterons at a dose and energy sufficient to provide significant vertical electrical isolation from underlying regions of the epitaxial layer semi-insulating with minimal detrimental effect on the electrical characteristics of the semiconductor layer.