Semimetal Semiconductor Heterojunction Devices

Publishing Venue

IBM

Related People

Laff, RA: AUTHOR

Abstract

These devices utilize a new type of rectifying junction composed of a heterojunction between a semimetal and a semiconductor, the interface between the two materials to be of matched lattice parameter. Such matching lattice parameter is obtained by proper choice of materials and crystalline directions, and is produced by epitaxial growth of one material on the other.

Semimetal Semiconductor Heterojunction Devices

These devices utilize a new type of rectifying junction composed of a heterojunction between a semimetal and a semiconductor, the interface between the two materials to be of matched lattice parameter. Such matching lattice parameter is obtained by proper choice of materials and crystalline directions, and is produced by epitaxial growth of one material on the other.

For example, the lattice atoms in the trigonal plane of the semimetal bismuth (rhombohedral structure) form an equilateral triangle of dimension ``a'' = 4.54 angstroms. The atoms of lead or tellurium in the compound semiconductor PbTe, in the (111) plane of the face-centered cubic lattice, form triangles of edge distance 4. 55 angstroms. Such close matching provides for good epitaxy.

In another example, the semimetal antimony has an ``a'' distance of 4. 30 angstroms. The semiconductors PbS and PbSe have equilateral distance with a (111) plane of 4. 20 angstroms and 4. 35 angstroms, respectively. Ternary compound semiconductors PbS(x)Se(1-x) or PbS(x)Te(1-x) can be grown to match exactly the lattice spacing of antimony.

Properties of these junctions are determined by band structure and surface contact properties of the two materials. The valence and conduction bands of semimetals are slightly overlapped and the material has equal numbers of electrons and holes. The lead salts have small band gaps and are partially ionic semiconductors in which the, type of material (electron or hole conduction) is us...