The Effects of gamma-ray Radiation on n-channel MOSFET

The response of an n-channel MOSFET to different energy gamma-ray irradiation is investigated as a function of dose rate. The radiation deposits energy by causing ionization in the oxide layer of the device. The ionization changes the charge excitation, charge transport, bonding and decomposition properties of the materials and thus affects the device parameters. The change in threshold voltage was observed before and after the exposure to the gamma-rays radiation. The transconductance of n-channel MOSFET is reduced by radiation induced interface traps. The mobility degradation is primarily due to interface trapped charge, but the effects of oxide-trapped charges were taken into account in order to properly describe the mobility behaviour. One failure mechanism caused by the radiation induced oxide charge in an n-channel MOSFET embedded in an integrated circuit is a shift from enhancement mode to depletion mode. The device will be turned on rather than off at zero gate voltage; consequently the excessive current may be generated in the circuit. It has been found that radiation-induced shifts in threshold voltage vary roughly with the cube of the oxide thickness.