Method of manufacture of photodiode

The method of forming one or more photodiodes comprising the steps of:

• placing a clean chip of lead-tin-telluride in a vacuum chamber;
• reducing the pressure in said chamber to approximately 10.sup.-6 torr;
• prebaking the chip;
• depositing a thin layer of lead on at least one selected portion of said chip;
• depositing a nonconducting evaporation inhibiting layer of SiO over said lead layer which is compatible with processing temperatures of at least 400.degree. C.;
• diffusing said layer of lead into said chip at a temperature of approximately 400.degree. C. for approximately 20 minutes;
• removing said chip from said vacuum chamber;
• coating said chip with a dielectric layer of insulating material;
• removing only that part of said non-conducting layer of SiO and said dielectric layer of insulating material which cover a surface area within each said selected portion to expose a portion of said surface area;
• returning said chip to said chamber;
• reducing the chamber pressure again to 10.sup.-6 torr;
• and
• depositing a lead-out structure of individual indium contacts over and through said nonconducting layer with a separate contact connected to said exposed area of each selected portion of said chip.