Rockwell International Corporation

US Government As Represented by the Secretary of the Army

Fermionics Corporation

Cheng-Chi Wang

Muren Chu

August H Vanderwyck

Joseph T Longo

Yet-Zen Liu

John E Clarke

John G Pasko

HgCdTe semiconductor material having an n-type epitaxial layer is grown on a substrate. A graded p-type epitaxial layer is grown on the n-type layer. The p-type layer is graded such that the large bandgap region is adjacent the heterojunction with the narrow bandgap region at the surface of this layer. The periphery of the p-type layer is then etched to expose the large bandgap material. A HgCdTe passivation layer may then be formed on the p-type layer. A resultant structure is then mesa etched. A metal, such as indium, is formed along the walls of the mesa structure. Indium is selected to form a good ohmic contact with the n-type layer and a Schottky barrier with the large bandgap exposed edge of the p-type layer. In this way, the PN junction is passivated at the large bandgap material. The remaining narrow bandgap material in the p-type will form a good ohmic contact to a metal contact formed on this layer.

Method of making an infrared detector

Disclosed is a method of growing a layer of CdTe on HgCdTe by liquid phase epitaxy. The solution for growth comprises Sn and Hg with a small amount of CdTe. A typical composition is Sn:Hg:CdTe=36:5:0.15 parts by weight. The growth temperature is a function of the amount of CdTe in solution. For the typical composition stated, the growth temperature is about 520.degree. C. The layers were grown on (111)A oriented CdTe substrates. The HgCdTe epilayer with a desired Cd composition is first grown, and an epilayer of CdTe is subsequently grown on the HgCdTe epilayer. The cross-diffusion at the CdTe/Hg.sub.1-x Cd.sub.x Te interface has been as small as 0.3 .mu.m for the thin CdTe epilayer. The first CdTe/HgCdTe heterojunction sensitive to .about.2.8 .mu.m at 77K has been demonstrated.

Method for growing an epitaxial layer of CdTe on an epitaxial layer of

Disclosed is a method of growing a layer of CdTe on HgCdTe by liquid phase pitaxy. The solution for growth comprises Sn and Hg with a small amount of CdTe. A typical composition is Sn:Hg:CdTe=36:5:0.15 parts by weight. The growth temperature is a function of the amount of CdTe in solution. For the typical composition stated, the growth temperature is about 520.degree. C. The layers were grown on (111)A oriented CdTe substrates. The HgCdTe epilayer with a desired Cd composition is first grown, and an epilayer of CdTe is subsequently grown on the HgCdTe epilayer. The cross-diffusion at the CdTe/Hg.sub.1-x Cd.sub.x Te interface has been as small as 0.3 .mu.m for the thin CdTe epilayer. The first CdTe/HgCdTe heterojunction sensitive to .about.2.8 .mu.m at 77.degree. K. has been demonstrated.

Liquid-phase epitaxial growth of cdTe on HgCdTe

Disclosed is a semi-open method of growing an epitaxial HgCdTe layer on a CdTe substrate, including the steps of placing the CdTe substrate and a growth solution of Hg, Cd, and Te within a pressure and temperature controlled container, flowing an inert gas under pressure through the container to reduce the vaporization of Hg from the solution, establishing a cooling zone within the container to condense Hg vaporized from the solution, increasing the temperature of the solution for a time sufficient to react the Hg and Cd with the Te in the solution, reducing the temperature of the solution, establishing contact between the solution and the substrate, maintaining the solution at a temperature sufficient to melt the substrate for a time sufficient to eliminate a Hg vapor diffused layer, reducing the temperature of the solution to near the saturation temperature, and reducing the temperature of the solution at a rate sufficient to cause the solution to crystallize in an HgCdTe layer on the CdTe substrate.

Semi-open liquid phase epitaxial growth system

A semi-open method for growing an epitaxial layer on a substrate by increasing the pressure, refluxing the volatile components, contacting the substrate with the melt solution, and reducing the solution temperature.

A low-leakage, heterojunction photodiode for use as a detector sensitive to infrared radiation is provided. The diode structure comprises a PbTe substrate of n-type conductivity with an n-type epitaxial buffer layer on the substrate and an epitaxial active layer on the buffer layer. The buffer layer is either Pb.sub.(1-x) S.sub.x Te or Pb.sub.1-x Se.sub.x Te with the atomic fraction of S or Se, x, being greater than 0 but less than 0.1. The active layer is Pb.sub.1-y Sn.sub.y Te with the atomic fraction of Sn, y, being greater than 0 but less than 0.3. There is a p-n junction created in the active layer with the n side of the junction being adjacent the buffer layer. Metal is deposited on the substrate and on the active layer to provide electrical contact to the diode.

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Thousand Oaks, CA, United States of America

Cheng-Chi Wang