Investigation Of Programming And Erasing Characteristics Of Nonvolatile Quantum Dot Floating Gate Memory Based On GaAs Substrate

In today's information society,greater storage capacity,faster read and write speed,higher data security and lower power consumption is the requirements for the memory performance,which makes the size of memory devices continue to decrease.However,reduced size will lead to increased leakage and reduce data security,which is an obstacle to the further development of memory.Using discrete quantum dots to instead of the traditional continuous floating gate as a storage layer has caused the researchers' s concern in recent years because of its low operating voltage,low leakage and other advantages.Additionally,since gallium arsenide has the advantages of high speed performance and low power dissipation compared with traditional Si substrate,the quantum dot floating gate storage(QDNVM)technology based on GaAs substrate will play an important role in the next generation of non-volatile storage technology applications.In this paper,the characteristics of quantum dot floating gate memories with GaAs as substrate are mainly studied from both theoretical and experimental aspects.Theoretically,we study the effects of substrate materials and tunneling materials on the memory programming characteristics with Silvaco TCAD simulation software,which use ATLAS simulator to establish the model of QDNVM and use CHEI as the programming mechanism.The simulation results show that GaAs substrate materials can achieve better programming characteristics.In addition,by considering the Coulomb blocking effect and the quantum confinement effect of QDs,the FN tunneling mechanism is used to establish the programming and erasing characteristics model of the quantum dot floating gate memory cell.On the basis of verifying the correctness of the model.The effects of tunneling layer thickness,quantum dot density,temperature and gate voltage on memory programming and erasure characteristics are studied.The results show that the lower the temperature,the larger the gate voltage and the smaller thickness of the tunneling layer is benefit to improve programming and erasing speed.Experimentally,in this paper,we fabricated Al / ZrO2 / Si / ZrO2 / GaAs memory cell,in which the thin film of silicon was fabricated by magnetron sputtering process,and Si quantum dots were fabricated on the basis of the principle of film aggregation.Then the devices were annealed at three different temperatures including 400 ?,500 ?,600 ?and the storage window of the device was obtained by measuring the C-V characteristics of the memory cell.The experimental results show that the device has the largest memory window at an annealing temperature of 400 ?,and the storage window gradually decreases with the annealing temperature increasing.So a reasonable annealing temperature has a significant impact on the storage performance of the device.