Self-organized quantum dots for future semiconductor memories

A memory structure based on self-organized quantum dots (QDs) combining the advantages of dynamic random access memory (DRAM) and flash memory which enables extremely fast write times (<1 ns) together with long storage times ( years) at room temperature is presented. A storage time of 1.6 s at 300 K in InAs/GaAs QDs with an additional Al0.9Ga0.1As barrier—100 times longer than in a DRAM—is demonstrated. Much longer retention times of 106 years are predicted for GaSb QDs in an AlAs matrix. A minimum write time of 6 ns is currently obtained for InAs/GaAs QDs, of the order of those for present DRAMs. An even faster write time below 1 ns, only limited by charge carrier capture and relaxation times (in the order of picoseconds), is predicted for a slightly improved device structure.