Electrical characteristics and memory behavior of Ge 3N 4GaAs MIS devices

MIS devices have been fabricated by the low temperature chemical vapor deposition of Ge ₃N ₄ on n-GaAs. From the current-voltage data an estimate of the Ge ₃N ₄ dielectric constant is made as 6.3 ± 0.2 and devices exhibit a breakdown field strength of ∼ 5 × 10 ⁶ V/cm. Capacitance and conductance measurements have been performed to investigate the electrical characteristics of the Ge ₃N ₄GaAs interface. The interface properties of the devices are found to depend on the Ge ₃N ₄ deposition parameters. No major hysteresis is observed in the C-V plot and under large negative gate bias, the capacitance increases as the measurement frequency is lowered. Interface state distribution, evaluated from the conductance data, is found to have a minimum density of states of 2 × 10 ¹¹ cm ^-2 eV ^-1 with a distinct shoulder between 0.4 and 0.55 eV from the conduction band. This shoulder is assigned to an electron trap level and from thermally stimulated current measurements we obtained the density of traps as 3 × 10 ¹⁷ cm ^-3. GaAs-MNOS devices have also been fabricated and their charge storage properties have been studied. Pulse voltages as large as 30-35 V are needed to write/erase the memory in the devices.