Browse Prior Art Database

New Type of Superlattice

IP.com Disclosure Number: IPCOM000089614D
Original Publication Date: 1977-Nov-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 41K

Publishing Venue

IBM

Related People

Chang, LL: AUTHOR [+4]

Abstract

A man-made superlattice consists of a periodic structure by alternating two semiconductor materials, a and b. Superlattices, which have been experimentally and theoretically pursued so far, have an energy diagram as shown in Fig. 1, where E(g) is the forbidden gap; E(ca) and E(ca) are the bottoms of the conduction bands for a and b, respectively; and E(va) and E(vb) are the tops of the valence bands for a and b, respectively. As seen in the figure, the conduction-band edges, E(ca) and E(cb), are located far from the valence-band edges, E(va) and E(vb), in energy. The first subbands in the conduction and valence bands, and the energy gap E(g), are also shown in Fig. 1. Regarding this type of superlattice, see U.S. Patents 3,626,257 and 3,626,328.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 70% of the total text.

Page 1 of 2

New Type of Superlattice

A man-made superlattice consists of a periodic structure by alternating two semiconductor materials, a and b. Superlattices, which have been experimentally and theoretically pursued so far, have an energy diagram as shown in Fig. 1, where E(g) is the forbidden gap; E(ca) and E(ca) are the bottoms of the conduction bands for a and b, respectively; and E(va) and E(vb) are the tops of the valence bands for a and b, respectively. As seen in the figure, the conduction-band edges, E(ca) and E(cb), are located far from the valence- band edges, E(va) and E(vb), in energy. The first subbands in the conduction and valence bands, and the energy gap E(g), are also shown in Fig. 1. Regarding this type of superlattice, see U.S. Patents 3,626,257 and 3,626,328.

A new type of superlattice is shown in Figs. 2A and 2B, where the bottom of the conduction band E(ca) in the material A is located close to the top of the valence band E(vb) in the material B, in energy. In this case, a strong interaction between the two neighboring bands gives rise to a highly nonlinear energy-wave vector relationship, and creates generally a narrow energy-gap, as shown. This energy gap depends strongly on the thicknesses of layers a and b. Thus, a desired energy gap can be obtained by adjusting the thicknesses: the thinner the layers, the larger the energy gap. Thus, the largest energy gap can be achieved by the alternating monolayer structure.

The energy-momentum relationship...