Development of a one transistor dynamic RAM for the AlGaAs/GaAs HIGFET technology

Modern VLSI integrated systems normally require large dynamic memory registers. To date, there has been little progress toward developing such memory elements for the GaAs heterojunction field effect transistor (HIGFET) technology. Toward this goal, we have studied the long term retention of minority carriers in potential wells at the AlGaAs/GaAs interface. Using a deep depletion capacitance-voltage (C-V) technique, we have measured the storage time of holes at the AlAs interface in the dark as a function of temperature from 175 K to 77 K. Storage times are thermally activated, with an activation energy of 0.37 eV. At 77 K, the storage time is greater than 220 hours, or 9 days. Using an AlAs-GaAs superlattice barrier, we measure an activation energy of 0.17 eV and a storage time at 77 K of 34 hours. These times are far in excess of what is needed to construct a one-transistor dynamic RAM for the GaAs HIGFET technology.