New floating-gate AlGaAs/GaAs memory devices with graded-gap electron injector and long retention times

AlGaAs/GaAs floating-gate memory devices are reported. Compared with conventional Si-based floating-gate device this structure operates on a different injection method. Electrons are injected from the control gate into the floating gate using AlGaAs graded-gap barrier. This has the advantage of significantly smaller WRITE voltages. Charge retention times ranging from 2 s at 300 K to 4 h at 140 K have been measured. The extrapolated storage time at 77 K is approximately 700 years. From a functional point of view, these electrically alterable read-only memory (EAROM) structures are promising also for dynamic random-access memory (DRAM) or static random-access memory (SRAM) applications depending on the operating temperatures.<
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