Direct tunneling diode structure with a multilayer charge injection barrier

We report the fabrication and testing of a silicon-based tunnel diode struc ture that incorporates a multilayer tunneling dielectric. The barrier consi sts of two thermally grown silicon oxide layers of direct tunneling thickne ss, similar to 3.5 nm each, separated by an ultrathin nanocrystalline silic on layer approximately 5 nm thick. The diode displays current-voltage chara cteristics that are similar to those of a Fowler-Nordheim device, with a st rong current turn-on beyond threshold positive and negative biases, and a " window" region between these two levels where charge transport across the b arrier is negligible. In contrast to Fowler-Nordheim devices, the barrier d oss not appear to degrade significantly when biased in either of its conduc tion regimes. This property is attributed to the intrinsic degradation resi stance of direct tunnel oxides. Additionally, capacitance-voltage character istics show that the structure is of high quality. Because of its current-v oltage and endurance capabilities, this structure shows promise for nonvola tile memory and other applications which require improved endurance and cha rge retention. (C) 1998 American Institute of Physics. [S0003-6951(98)01451 -X].