Binary synaptic connections based on memory switching in a-Si:H

Nonvolatile, associative, electronic memory based on neural network models promises high (∼109 bits/cm2) information storage density since the information would be stored in a matrix of simple two terminal, passive interconnections. Device considerations dictate that such connections should be weak. For example, connections with ∼106Ω resistance are quite adequate in a 1000×1000 matrix (∼250K bit ROM). Irreversible memory switching in hydrogenated amorphous silicon (a‐Si:H) thin films is studied as a candidate mechanism for a prototype binary PROM matrix. The memory switching in a‐Si:H is current induced and requires very low energy (∼1 nanojoule for 1 μm2 area of a 0.2 μm thick film) to switch from ∼1010Ω to ∼105Ω. Resistivity‐tailored, amorphous Ge1−xMx (M=Al, Cu) provides the (synaptic) ballast resistor in the microswitch. A novel side saddle test structure exhibits a potential for a very high density binary connection matrix.