| 摘要 |
1,086,228. Photocathodes; semi-conductors. PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd. Nov. 29, 1965 [Dec. 2, 1964], No. 50530/65. Headings H1D and H1K. A photocathode consists of a P-type semiconductor activated with an alkali metal, with or without oxygen, the semi-conductor comprising a compound of one of the elements of the third column of the periodical system, e.g. B, Al, Ga, In, and one of the elements of the fifth column, e.g. N, P, As, Sb, or mixed crystals of these compounds, with an energy gap lying between 1À1eV and 1À6eV. The semiconductor may be gallium arsenophosphide, or gallium arsenide having an acceptor concentration of 10<SP>18</SP>-10<SP>20</SP>, e.g. 4 x 10<SP>19</SP>, atoms per cm.<SP>3</SP>, the acceptor being Zn, Cd, Hg or Te. The gallium arsenide may contain ¢% of gallium phosphide or gallium antimonide. The photocathode may be used in a photo-cell, a photomultiplier, an image intensifier, an image iconoscope, or an image orthicon. During manufacture of a photo-cell, a gallium arsenide crystal may be severed by a knife supported by a movable metal part of the sealed envelope, Fig. 1 (not shown), before application of a monoatomic caesium layer by evaporation. Alternatively, a P-type semi-conductor may be applied by vaporization to a curved molybdenum plate, or to a portion of the tube envelope, and exposed to caesium vapour, to produce a layer 1000Š thick.
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