Enhanced Band-to-Band-Tunneling-Induced Hot-Electron Injection in p-Channel Flash by Band-gap Offset Modification

A novel p-channel flash device with a SiGe layer is proposed, which is based on the analysis made with the simulator MEDICI, to enhance the band-to-band-tunneling current and improve the programming speed. The programming biases of the p-channel flash device can be reduced with an equal programming speed. Simulation results show that more than one hundred times enhancement in the programming speed or 35% reduction of the drain voltage can be achieved in the proposed p-channel flash device with a 40% Ge content in the surface SiGe layer. In addition, a Si-cap layer is inserted between the SiGe and the tunneling oxide to obtain a high-quality interface and to optimize the cell structure.