Retention Characteristics Of Quantum Dots Floating Gate Memory Based On GaAs

With the development of information technology,the non-volatile memory is used more and more widely.The use of dispersed quantum dots instead of continuous poly-silicon,has been of great concern.Because of its excellent fatigue resistance,low power consumption and small size,quantum dots have become a hot spot in the research of semiconductor storage technology.At the same time,With high electron mobility and carrier injection rate,GaAs is better than Si.In this thesis,the theoretical and experimental researches are carried out based on the above contents,and retention model of quantum gate floating gate memory based on GaAs and the effect of annealing temperature on the storage characteristics are studied.In the theory,?1?A retention model for single-layer quantum dots structure floating gate memory is established,based on the relationship between direct tunneling current density and threshold voltage offset of quantum dots floating gate memory,the retention characteristics of Si,Ge,InP quantum dots as a device storage layer are simulated.According to the quantum confinement effect,with the decrease of the diameter of quantum dots,the tunneling barrier decreases and the retention capacity of devices decreases.At the same time,the density of quantum dots increases within a certain range,retention ability enhance;while tunneling layer thickness increases,the tunneling probability decreases,retention capacity become stronger;The simulation results of ZrO₂,Al₂O₃,HfO₂ as control layer and tunneling layer show that the appropriate dielectric layer material can not only reduce the size of the device,but also get a good retention.?2?A double-layer quantum dots floating gate memory model is established,combined with the analysis of charge transport mechanism,it founds that the underlying quantum dots will block transport process of charge in the upper quantum dots because of quantum confinement effect and Coulomb block effect,thereby reducing the probability of charge into and out of the upper quantum dots;Then,the retention characteristics and programming/erasing characteristics of single layer and double layer structure are simulated respectively.The results show that the storage structure of the double-layer quantum dots can block the charging and discharging process of the upper quantum dots to some extent,Although the programming/erasing speed is slowed down,it can obviously improve the retention ability.In the experiment,the stacked gate stack structure of Al/HfO₂/Si/HfO₂/TaON/GaAs is designed and fabricated.The relationship between the storage performance of the device and the annealing temperature is analyzed by measuring the electrical properties.The results show that the storage window of the samples with different annealing temperature is in the 1²V,which shows good charge storage capacity.Then from the I-V measurement results,the annealing temperature can effectively improve the quality of HfO₂ dielectric layer,so as to obtain a better tunneling layer and control layer,which can help to obtain better charge storage performance.