US 6,208,005 B1 · Mercury-based quaternary alloys of infrared sensitive materials

Abstract

A variable bandgap infrared absorbing material, Hg1-x Cdx Te, is manufactured by use of the process termed MOCVD-IMP (Metalorganic Chemical Vapor Deposition-Interdiffused Multilayer Process). A substantial reduction in the dislocation defect density can be achieved through this method by use of CdZnTe layers which have a zinc mole fraction selected to produce a lattice constant which is substantially similar to the lattice constant of HgTe. After the multilayer pairs of HgTe and Cd0.944Zn0.056Te are produced by epitaxial growth, the structure is annealed to interdiffuse the alternating layers to produce a homogeneous alloy of mercury cadmium zinc telluride. The mole fraction x in Hg1-x(Cd0.944Zn0.056)xTe can be varied to produce a structure responsive to multiple wavelength bands of infrared radiation, but without changing the lattice constant. The alloy composition is varied by changing the relative thicknesses of HgTe and Cd0.944Zn0.056Te. A similar structure can also be fabricated using HgTe and lattice matched CdTe1-ySey. Thus, a multi-band infrared absorbing material structure can be fabricated which has reduced dislocation defects, and thereby produce detectors with improved performance.

Claims35

Dependent claims

A variable bandgap infrared absorbing semiconductor material structure, comprising:

a substrate,
a buffer layer epitaxially grown on said substrate, said buffer layer comprising cadmium zinc telluride, and
a homogeneous alloy structure of mercury cadmium zinc telluride formed by epitaxial growth on said buffer layer of alternating layers of mercury telluride and cadmium zinc telluride, said cadmium zinc telluride layers and said buffer layer having a zinc mole fraction to produce therein a lattice constant substantially similar to the lattice constant of said mercury telluride layers, and wherein said mercury telluride and cadmium zinc telluride layers are annealed to form said homogeneous alloy structure.

A variable bandgap infrared absorbing semiconductor material structure responsive to at least two different bands of infrared radiation, comprising:

a substrate,
a buffer layer epitaxially grown on said substrate, said buffer layer comprising cadmium zinc telluride,
a first homogeneous alloy structure of mercury cadmium zinc telluride formed on said buffer layer by epitaxial growth of alternating layers of mercury telluride and cadmium zinc telluride, said first homogeneous alloy structure cadmium zinc telluride layers and said buffer layer having a zinc mole fraction to produce therein a lattice constant substantially similar to the lattice constant of said mercury telluride layers, and wherein said first homogeneous alloy structure of mercury telluride and cadmium zinc telluride layers is annealed to form said first homogeneous alloy structure, said first homogeneous alloy structure further having a zinc mole fraction for producing therein a bandgap responsive to infrared radiation within a first band, and
a second homogeneous alloy structure of mercury cadmium zinc telluride formed on said first alloy structure by epitaxial growth of alternating layers of mercury telluride and cadmium zinc telluride, said second homogeneous alloy structure cadmium zinc telluride layer having a zinc mole fraction produce therein a lattice constant substantially similar to the lattice constant of said mercury telluride layers, and wherein said second homogeneous alloy structure of mercury telluride and cadmium zinc telluride layers is annealed to form said second homogeneous alloy structure, second homogeneous alloy structure further having a ratio of cadmium to mercury producing a band gap therein responsive to infrared radiation within a second band.

1 more element

A variable bandgap infrared absorbing semiconductor material structure responsive to short wave, medium wave and long wave bands of infrared radiation, comprising:

a substrate,
a buffer layer epitaxially grown on said substrate, said buffer layer comprising cadmium zinc telluride,
a first homogeneous alloy structure of mercury cadmium zinc telluride formed on said buffer layer by epitaxial growth of alternating layers of mercury telluride and cadmium zinc telluride, said first structure cadmium zinc telluride layers and said buffer layer having a zinc mole fraction to produce therein a lattice constant substantially similar to the lattice constant of said mercury telluride layers, and wherein said first homogeneous alloy structure of mercury telluride and cadmium zinc telluride layers is annealed to form said first homogeneous alloy structure, said first homogeneous alloy structure further having a cadmium mole fraction for producing therein a bandgap responsive to short wave infrared radiation,
a second homogeneous alloy structure of mercury cadmium zinc telluride formed on said first homogeneous alloy structure by epitaxial growth of alternating layers of mercury telluride and cadmium zinc telluride, said second homogeneous alloy structure cadmium zinc telluride layer having a zinc mole fraction to produce therein a lattice constant substantially similar to the lattice constant of said mercury telluride layers, and wherein said second homogeneous alloy structure of mercury telluride and cadmium zinc telluride layers is annealed to form said second homogeneous alloy structure, said second homogeneous alloy structure further having a cadmium mole fraction for producing a bandgap therein responsive to medium wave infrared radiation, and
a third homogeneous alloy structure of mercury cadmium zinc telluride formed on said second alloy structure by epitaxial growth of alternating layers of mercury telluride and cadmium zinc telluride, said third homogeneous alloy structure cadmium zinc telluride layer having a zinc mole fraction to produce therein a lattice constant substantially similar to the lattice constant of said mercury telluride layers, and wherein said third homogeneous alloy structure of mercury telluride and cadmium zinc telluride layers is annealed to form said third homogeneous alloy structure, said third structure further having a cadmium mole fraction for producing a bandgap therein responsive to long wave infrared radiation.

2 more elements