Abstract A transmission photocathode device of the negative-electronaffinity type is disclosed. The device comprises epitaxially grown P type semiconductor layers and an alkali metal or alkali metal-oxygen work-function-reducing activation layer. Also disclosed is a novel method for making a negative-electronaffinity transmission photocathode device. The method enables a photocathode device to be made by the serial epitaxial growth of p type layers of a II-VI or III-V semiconductor on a semiconductor substrate. The method provides for a virtually perfect lattice match between the semiconductor layers thereby increasing the efficiency of the photocathode by eliminating lattice defects which would otherwise exist at the interface between the transmitting material and the absorbing material.
THE METHOD FOR MAKING A TRANSMISSION PHOTOCATHODE DEVICE COMPRISING THE STEPS OF: A EPITAXIALLY GROWING A FIRST LAYER OF A P TYPE SEMICONDUCTOR MATERIAL ON A SUBSTRATE OF THE SAME SEMICONDUCTOR MATERIAL AS THAT OF THE FIRST LAYER, B EPITAXIALY GROWING A SECOND SEMICONDUCTOR LAYER UPON SAID P TYPE FIRST LAYER, SAID SECOND SEMICONDUCTOR LAYER BEING OF A P TYPE SEMICONDUCTOR MATERIAL HAVING A HIGHER BANDGAAP ENERGY THAN THE SIMICONDUCTOR MATERIAL OF SAID P TYPE FIRST LAYER, C. REMOVING SAID SUBSTRATE TO EXPOSE SAID P TYPE FIRST LAYER, AND D. COATING SAID EXPOSED P TYPE FIRST LAYER WITH A WORKFUNCTION-REDUCING ACTIVATION LAYER.
Claim 2
Independent Claim
102 words
THE METHOD FOR MAKING A TRANSMISSION PHOTOCATHODE DEVICE COMPRISING THE STEPS OF: A EPITAXIALLY GROWING A FIRST LAYER OF A P TYPE SEMICONDUCTOR MATERIAL ON A SUBSTRATE OF THE SAME SEMICONDUCTOR MATERIAL AS THAT OF THE FIRST LAYER, B EPITAXIALY GROWING A SECOND SEMICONDUCTOR LAYER UPON SAID P TYPE FIRST LAYER, SAID SECOND SEMICONDUCTOR LAYER BEING OF A P TYPE SEMICONDUCTOR MATERIAL HAVING A HIGHER BANDGAAP ENERGY THAN THE SIMICONDUCTOR MATERIAL OF SAID P TYPE FIRST LAYER, C. REMOVING SAID SUBSTRATE TO EXPOSE SAID P TYPE FIRST LAYER, AND D. COATING SAID EXPOSED P TYPE FIRST LAYER WITH A WORKFUNCTION-REDUCING ACTIVATION LAYER.
Claim 3
Dependent Claim
26 words
The method of claim 1 wherein said steps of epitaxially growing the first and second semiconductor layers are accomplished by the method of liquid phase epitaxy.
Claim 4
Dependent Claim
26 words
The method of claim 2 wherein said step of removing said substrate to expose said P type first layer is accomplished by etching in an acid.
Claim 5
Dependent Claim
26 words
The method of claim 1 wherein the steps of epitaxially growing the first and second semiconductor layers are accomplished by the method of vapor phase epitaxy.