Effect of a buried superlattice on the dynamic storage of electrons at the AlGaAs/GaAs heterojunction

A buried five-period 94 Å Al0.3Ga0.7As/ 56 Å GaAs superlattice is employed to improve the dynamic retention of electrons at an AlGaAs/GaAs heterojunction. The improvement is attributed to the impurity trapping and gettering properties of this superlattice and the amount of time our molecular beam epitaxy system had been closed. Electron retention time constants of 29 s were obtained at a temperature of 77 K. This is more than 200 times longer than previously reported time constants and more than adequate for dynamic logic or memory applications compatible with AlGaAs/GaAs heterojunction field-effect transistors.