Series resonant tunneling diodes as a two-dimensional memory cell

A state-of-the-art multiple-variable memory cell that can provide many-quanta stable states is proposed. The basic cell is composed of two resonant tunneling diodes (RTDs) connected in series with a load. Access lines are connected to every joint between any two devices. When properly biased, the cell can have (N+1)² or more stable quantized operating states that are defined by two variables, where N is the number of current peaks of the RTD. A cell with nine stable states has been implemented and demonstrated by a breadboard circuit using two two-peak RTDs