Microelectronic cooling using the Nottingham effect and internal field emission in a diamond (wide-band gap material) thin-film device

We propose a method for heat dissipation in microelectronic devices which uses internal field emission through the interface of a composite thin-film device {i.e., metal [semiconductor (S)]/ chemical vapor deposition doped diamond [wide-band gap (WBG) material]} in conjunction with a heat sink. These composite thin-film devices are of micron to submicron dimensions and composed of materials which can be integrated with existing semiconductor technology. As distinct from conventional field emission into vacuum and thermionic devices, the relatively high metallic (S) work function (> 2 eV) is here circumvented by use of internal field emission through a Schottky barrier at a metal/diamond (WBG) interface. It is the large band gap in these materials which introduces a filtering effect on the injected electrons which allows one to restrict the tunneling of electrons through the Schottky barrier from states below the Fermi energy, epsilon(F). For applied fields below a certain value, the average energy of the field-emitted electrons is greater than the average energy of the electrons which replace them, leading to the so-called Nottingham cooling. It has recently been shown that the replacement electrons have an energy up to 100 meV or more lower than epsilon(F), enhancing the cooling process by field emission. Using a kinetic field emission formalism, a tip density of 10(7)/cm(2), a local electron gas temperature of 500 K, and a tip radius of 50 nm (blunt tip), an average cooling rate per area of 1.6 W/cm(2) can be achieved. Higher tip densities lead to average heat dissipation rates which can scale up to 100 W/cm2 or higher, rates competitive with or exceeding other techniques for thermal dissipation (i.e., thermoelectric and thermionic). (C) 1999 American Institute of Physics. [S0003-6951(99)01440-0].