Abstract: A multi-stage cooler is formed from monolithically integrated thermionic and thermoelectric coolers, wherein the thermionic and thermoelectric coolers each have a separate electrical connection and a common ground, thereby forming a three terminal device. The thermionic cooler is comprised of a superlattice barrier surrounded by cathode and anode layers grown onto an appropriate substrate, one or more metal contacts with a finite surface area deposited on top of the cathode layer, and one or more mesas of different areas formed by etching around the contacts to the anode layer. The thermoelectric cooler is defined by metal contacts deposited on the anode layer or the substrate itself. A backside metal is deposited on the substrate for connecting to the common ground.

Abstract: A multi-stage cooler is formed from monolithically integrated thermionic and thermoelectric coolers, wherein the thermionic and thermoelectric coolers each have a separate electrical connection and a common ground, thereby forming a three terminal device. The thermionic cooler is comprised of a superlattice barrier surrounded by cathode and anode layers grown onto an appropriate substrate, one or more metal contacts with a finite surface area deposited on top of the cathode layer, and one or more mesas of different areas formed by etching around the contacts to the anode layer. The thermoelectric cooler is defined by metal contacts deposited on the anode layer or the substrate itself. A backside metal is deposited on the substrate for connecting to the common ground.