US 4,665,415 AGranted

Semiconductor device with hole conduction via strained lattice

AssigneeInternational Business Machines Corporation

InventorsLeo Esaki, Leroy L. Chang, Wen-I Wang

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Abstract

A field-effect transistor includes a conduction channel between a source terminal and a drain terminal, which channel employs holes as the charge carriers. The conduction channel is disposed within a layer of material comprising a group III-V compound of the periodic table and having a crystalline lattice structure which is stressed in two dimensions by means of epitaxial growth upon a thicker and rigid supporting layer comprising a different group III-V compound having a larger lattice spacing. The layer having the conduction channel is relatively thin being on the order of a few electron wavelength in thickness. The stretching of the layer having the conduction channel shift the energy levels of holes therein to remove the degenerate state thereof, thereby elevating light holes to an energy level characterized by increased mobility.

Claims12

Dependent claims

A field-effect transistor comprising:

a source terminal, a drain terminal, and a gate terminal;
a first layer of semiconductor material comprising a first compound of a group III element with a group V element of the periodic table formed with a crystalline lattice structure having a first lattice spacing, said source terminal and said drain terminal being spaced apart from each other and in contact with said first layer, said gate terminal being spaced apart from said first layer;
a second layer of semiconductor material comprising a second compound of a group III element with a group V element formed with a crystalline lattice structure having a second lattice spacing, said second layer extending between said source terminal and said drain terminal and being located between said first layer nd said gate terminal and electrically connected to said gate terminal;
and wherein
said second lattice spacing of said second compound in an unstressed state is less than said first lattice spacing of said first compound in an unstressed state, said second layer being formed by epitaxy as an epitaxial layer upon said first layer, the epitaxy straining said second compound to equalize said lattice spacings and introducing a stress which shifts an energy level of charge carriers for increased mobility of the charge carriers;
and wherein
the thickness of said first layer is at least approximately an order of magnitude greater than the thickness of said second layer to be sufficiently rigid for stressing said second layer, said second layer being sufficiently thin to retain the strain induced by the difference in lattice spacing, there being a conduction channel established in said second layer by modulation doping induced by said gate terminal.

4 more elements

A semiconductor device fabricated of a set of layers of semiconductor compounds of elements from groups III and V of the periodic table, and having a conduction channel for holes in one of said layers comprising:

a first layer of said set of layers formed of a first one of said compounds;
a second layer of said set of layers formed of a second of said compounds different from said first compound, the compounds in respective ones of said first and said second layers having crystalline structures with different lattice spacings, said conduction channel being located in said first layer;
a set of terminals electrically coupled to said conduction channel in said first layer;
and wherein
said first layer is constructed as an epitaxial layer upon said second layer, the difference in lattice spacing of said second layer from said first layer introducing a strain in said first layer during epitaxial growth of said first layer upon said second layer, said strain shifting energy levels of holes in said first layer to provide mobile holes in said conduction band;
and wherein
the thickness of said second layer is at least approximately an order of magnitude greater than the thickness of said first layer to be sufficiently rigid for stressing said first layer, said first layer being sufficiently thin to retain the strain induced by the difference in lattice spacing.

4 more elements

Dependencies are inferred from the claim text.