STORAGE ARRAY HAVING DC STABLE CONDUCTIVITY MODULATED STORAGE CELLS

The storage is fabricated in integrated circuit form, typically on a semiconductor chip, each storage cell being contained within a single isolated zone formed in the semiconductor chip. Each storage cell is DC stable and operates on a conductivity modulation principle, i.e. a cell conducts when it stores a binary "1" and the conductive state is maintained by conductivity modulation of an element of the cell, and the cell is non-conducting when storing a binary "0". In its most basic form, each cell includes at least two resistors (R2, R2 min ; R3, R3 min , R2''') formed in series in a P type semiconductor region (18, 20). At least one of the resistors, formed in a lightly doped portion of the P type region, is a variable resistor (R2, R2 sec , R2''') having both high and low values of resistance. The high value of resistance is changed to a low value of resistance by injecting electrons from a proximate N type semiconductor region. The low value of resistance is then maintained by the current conducted through the storage cell during standby.