Superlattice structures particularly suitable for use as thermoelectric materials

A superlattice structure comprising:

• alternating layers of two component materials;
• wherein one of the component materials consists essentially of an electrical insulating material and another of the component materials consists essentially of a semimetal material;
• and
• wherein the electrical insulating material comprises Pb.sub.1-y Eu.sub.y Te.sub.z Se.sub.1-z with 0.ltoreq.y.ltoreq.1, 0.ltoreq.z.ltoreq.1 and the semimetal comprises Bi.sub.x Sb.sub.1-x, 0.ltoreq.x.ltoreq.1.

A superlattice structure comprising:

• alternating layers of two component materials;
• wherein one of the component materials consists essentially of an electrical insulating material and another of the component materials consists essentially of a semimetal material;
• and
• wherein the electrical insulating material layers comprises EuTe.sub.1-x Se.sub.x with 0.ltoreq.x.ltoreq.1.

A superlattice structure comprising:

• alternating layers of two component materials;
• wherein one of the component materials consists essentially of an electrical insulating material and another of the component materials consists essentially of a semimetal material;
• and
• wherein the semimetal material comprises Bi.sub.x Sb.sub.1-x with 0.ltoreq.x.ltoreq.1.

A superlattice structure comprising:

• alternating layers of two component materials;
• wherein one of the component materials consists essentially of an electrical insulating material and another of the component materials consists essentially of a semimetal material;
• wherein the electrical insulating material further comprises quantum barrier layers and the semimetal material comprises quantum well layers alternating with respect to the quantum barrier layers;
• and
• wherein the quantum barrier layers further comprise europium.

A superlattice structure comprising:

• alternating layers of two component materials;
• wherein one of the component materials consists essentially of an electrical insulating material and another of the component materials consists essentially of a semimetal material;
• wherein the electrical insulating material further comprises quantum barrier layers and the semimetal material comprises quantum well layers alternating with respect to the quantum barrier layers;
• and
• wherein the quantum barrier layers comprise alkaline earth metals selected from the group consisting of strontium, barium, and calcium.

A superlattice structure comprising:

• alternating layers of two component materials;
• wherein one of the component materials consists essentially of an electrical insulating material and another of the component materials consists essentially of a semimetal material;
• and
• wherein the semimetal material comprises Pb.sub.1-x Sn.sub.x Te.sub.1-y Se.sub.y with 0.15.ltoreq.x.ltoreq.0.85 and 0.ltoreq.y.ltoreq.1.

An n-type thermoelectric element having a superlattice structure for use in fabricating thermoelectric devices comprising a plurality of alternating layers of:

• L.sub.1-y M.sub.y D.sub.z J.sub.1-z and
• Bi.sub.x R.sub.1-x ;
• where L is a material selected from the group consisting of Europium and Strontium;
• M is T Croup IV selected from the group consisting of Pb, Sn and Ge;
• D is a Group VI non-metal selected from the group consisting of Te, Se and S;
• J is a Group VI non-metal selected from the group consisting of Te, Se and S;
• R is a Group V material;
• D is not the same as J;
• 0.ltoreq.x.ltoreq.1;0.ltoreq.y.ltoreq.1;
• and
• 0.ltoreq.z.ltoreq.1.

A short-period superlattice structure for an n-type thermoelectric element used for forming a thermoelectric device comprising:

• a plurality of epitaxially grown alternating layers of materials A and B, where A and B are substantially lattice matched in a direction perpendicular to the direction of growth and are formed from materials which provide a thermoelectric figure of merit greater than 1.7;
• and
• the thickness of the layers of materials A and B and the number of layers of materials A and B within a period of the superlattice are formed such that E.sub.g.sup.s1 is approximately in the range of 0 kT to 8 kT, where k is Boltzman's constant, T is temperature and
• E.sub.g.sup.sl ={E.sub.gA d.sub.A +E.sub.gB d.sub.B }(d.sub.A +d.sub.B);
• where E.sub.g.sup.sl is the energy gap of the superlattice, E.sub.gA and E.sub.gB are the energy gaps of materials A and B, respectively, and d.sub.A and d.sub.B are the layer thicknesses of materials A and B, respectively.

A thermoelectric device having a plurality of thermoelectric elements comprising:

• at least a portion of the thermoelectric elements having a superlattice structure formed from alternating quantum barrier layers and quantum well layers;
• the quantum barrier layers formed from material L.sub.1-y M.sub.y D.sub.z .sub.1-z ;
• the quantum well layers formed from material Bi.sub.x R.sub.1-x;
• wherein L is an element selected from the group consisting of Eu, Sr, Ba, and Ca;
• M is a Group IV metal selected from the group consisting of Pb, Sn, and Ge;
• D is a Group VI non-metal selected from the group consisting of Te, Se, and S;
• J is a Group VI non-metal selected from the group consisting of Te, Se and S;
• R is a Group V element;
• D is not the same as J;
• 0.ltoreq.x.ltoreq.1;
• 0.ltoreq.y.ltoreq.1;
• 0.ltoreq.z.ltoreq.1;
• and
• the quantum barrier layers comprising electrical insulating material which is essentially nonconducting resulting in essentially all electrical current flowing only through the quantum well layers.

A superlattice structure formed on a substrate for use in fabricating thermoelectric elements for use in a thermoelectric device having an enhanced figure of merit, comprising:

• a buffer layer of Pb.sub.1-y Eu.sub.y Te formed on one surface of the substrate wherein 0.ltoreq.y.ltoreq.1;
• a plurality of alternating barrier layers and quantum well layers formed on the buffer layer opposite from the substrate with each barrier layer comprising Pb.sub.1-y Eu.sub.y Te wherein 0.ltoreq.y.ltoreq.1 and each quantum well layer comprising PbTe;
• and
• the superlattice structure extending generally uniformly from the buffer layer through the alternating barrier layers and quantum well layers.