Charge storage and data retention characteristics of forming gas-annealed Gd2O3-nanocrystal nonvolatile memory cell

Trapping characteristics of forming gas-annealed Gd2O3 nanocrystal (Gd2O3-NC) memories were studied in detail. The trapping energy can be obtained from the data retention characteristic for different absolute temperature (T). The discharging time (τ) was extracted from a linear fitting curve of the data retention characteristic. From the relationship between ln(1/τT2) and 1/kT, the trapping energy was evaluated. Based on the retention properties, the discharge mechanisms of electrons in shallow and deep traps are correlated to the charge loss time. The observed values of the trapping energy demonstrated that deep traps are passivated by hydrogen species after FGA treatment; the difference of programming and erasing (P/E) speed of the memories between the samples with- and without-FGA treatment can be explained by this passivation process. A band diagram is proposed to explain the behavior of the charge loss mechanism. The fact that the endurance of Gd2O3-NC memories are not significantly degraded by the FGA treatment indicates that, though the deep traps are passivated by hydrogen, the reliability of the Gd2O3-NC memories is not affected. The method of FGA treatment enables the determination of the discharge process in nanocrystal memories.