Thermal diode for energy conversion

A solid state thermionic converter of thermal energy, comprising:

• an emitter having at least a region comprising a first donor having a concentration Nd*;
• a first ohmic contact in electric and thermal communication with said emitter;
• a metal-semiconductor-interface-barrier-reduction layer between said first ohmic contact and said emitter;
• a collector;
• a second ohmic contact in electric communication with said collector;
• a gap region between said emitter and said collector in electric and thermal communication with said emitter and said collector, said gap region comprising a semiconductor, said semiconductor comprising a second donor having a concentration Nd, said concentration of said second donor being selected such that the natural logarithm of the ratio Nd*/Nd is between a numerical value greater than 0 and about 7.

A solid state thermionic converter of thermal energy, comprising:

• a plurality of plates Pi, with 1≦i≦m, where m is the total number of said plates, each one of said plates Pi having
• an emitter Ei having at least a region comprising a first donor having a concentration Nd*;
• a collector Ci;
• and
• a gap region Gi between said emitter Ei and said collector Ci in electric and thermal communication with said emitter Ei and said collector Ci, said gap region Gi comprising a semiconductor, said semiconductor comprising a second donor having a concentration Nd, said concentration of said second donor being selected such that the natural logarithm of the ratio Nd*/Nd is between a numerical value greater than 0 and about 7, and such that 1≦i≦m;
• wherein each plate Pj having an emitter Ej+1, a gap region Gj+1, and a collector Cj+1, so configured is connected in series with a group of an emitter Ej, a gap region Gj, and a collector Cj, for 1≦j≦(m−1), the indexes i and j being integers, and such that collector Cj is in electric communication with emitter Ej+1 for each j satisfying 1≦j≦(m−1).

A solid state thermionic converter of thermal energy, comprising:

• an emitter having at least a reaction product of Hg1−xCdxTe, x being in the range from about 0.08 to about 0.25, with a substrate comprising In;
• a collector;
• and
• a gap region between said emitter and said collector in electric and thermal communication with said emitter and said collector, said gap region comprising a semiconductor selected from the group consisting of n-type, p-type and intrinsic semiconductors.

A solid state thermionic converter of thermal energy, comprising:

• an emitter having at least a region comprising a first donor having a concentration Nd*;
• a gap region adjacent to and in electric and thermal communication with said emitter, said gap region comprising a semiconductor, said semiconductor comprising a second donor having a concentration Nd, said concentration of said second donor being selected such that the natural logarithm of the ratio Nd*/Nd is between a numerical value greater than 0 and about 7;
• a compensated region disposed between said gap region and said collector, said compensated region being configured to suppress electric current from said collector to said gap region;
• and
• a cold ohmic contact in electric and thermal communication with said gap region, wherein said cold ohmic contact comprises a recombination collector region next to said gap region.

A solid state thermionic converter of thermal energy, comprising:

• an emitter having at least a region comprising a first donor having a concentration Nd*;
• a compensated region;
• a gap region between said emitter and said compensated region, such that said gap region is in electric and thermal contact with said emitter and said compensated region, said gap region comprising a semiconductor, said semiconductor comprising a second donor having a concentration Nd, said concentration of said second donor being selected such that the natural logarithm of the ratio Nd*/Nd is between a numerical value greater than 0 and 7;
• and
• a collector in electric and thermal contact with said compensated region, said compensated region having p-type doping such that electric current from said collector to said gap region can be substantially suppressed while allowing thermionic current from said gap region to said collector.

A method for refrigeration by using a solid state thermionic converter, comprising:

• establishing externally an electric potential difference across a thermionic converter having
• a thermally insulated emitter having at least a region having a first donor concentration Nd*;
• a collector;
• a gap region between said emitter and said collector in electric and thermal communication with said emitter and said collector, said gap region comprising a semiconductor, said semiconductor comprising a second donor having a concentration Nd, said concentration of said second donor being selected such that the natural logarithm of the ratio Nd*/Nd is between a numerical value greater than 0 and about 7;
• and
• delivering a thermal load to said emitter such that said thermal load is cooled by heat flow as said externally established electric potential difference causes the flow of electric current between said emitter and said collector.