through the external circuit in use the electron emitters 108 emit narrow beams 614 of electrons onto the surface of the storage medium 110 that excite electron hole pairs near the surface of the medium because the medium 110 is reverse biased by the external circuit 604 the minority carriers that are generated by the incident electrons are swept toward the diode junction 610 electrons that reach the junction 610 are then swept across the junction accordingly minority carriers that do not recombine with majority carriers before reaching the junction 610 are swept across the junction causing a current flow in the external circuit 604 as described above writing is accomplished by increasing the power density of electron beams enough to locally alter the physical properties of the storage medium 110 where the medium 110 is configured as that shown in fig6 this alteration affects the number of minority carriers swept across the junction 610 when the same area is radiated with a lower power density read electron beam for instance the recombination rate in a written i e modified area 608 could be increased relative to an unwritten i e unmodified area 606 so that the minority carriers generated in the written area have an increased probability of recombining with minority carriers before they have a chance to reach and cross the junction 610 hence a smaller current flows in the external circuit 604 when the read electron.