ELECTRONIC EFFECTS OF ION MOBILITY IN SEMICONDUCTORS - MIXED ELECTRONIC-IONIC BEHAVIOR AND DEVICE CREATION IN SI-LI

Micrometer-sized homojunction structures can be formed by applying str ong electric pulses, at ambient temperatures, to Li-doped, floating zo ne n-Si. Two such junctions, arranged back to back, act as a transisto r, as evidenced by electron-beam-induced current and current-voltage m easurements, The structures are created during a time ranging from sim ilar to 100 ms to a few seconds, depending on the size of the structur e. The phenomenon is similar to what was observed earlier in CuInSe2 a nd was explained there by thermally assisted electromigration of Cu. I n the case of Si doped with Li we can use secondary-ion-mass spectrome try to detect the redistribution of Li after electric-field applicatio n. Such a redistribution is indeed found and corresponds to an n(+)-p- n structure with the p region extending at least similar to 20 mu m in to the bulk of Si. Structures created in Si doped with Li in this way are stable for at least 13 months after their creation. We ascribe thi s to the large difference between Li diffusivity at the local temperat ure that is reached during structure formation (similar to 400 degrees C; 10(-8) cm(2)/s) and at room temperature (similar to 10(-15) cm(2)/ s). (C) 1996 American Institute of Physics.