Quantum dot based non-volatile memory (QD-Flash) with fast write, erase, and read access of a few nanoseconds - Green Memory Concept

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The market for semiconductor memories is essentially divided between two memory types: On the one side there are the fast, but volatile Dynamic Random Access Memories (DRAM), which require the stored information to be cyclically refreshed, a process which leads to large energy consumption. On the other side there are the non-volatile Flash memories, which can store the information for more than 10 years, even without power supply, but suffer from a slow access time and bad endurance. A combination of the individual advantages of DRAM and Flash would yield an ideal memory with fast access and non-volatility, called holy grail of memories. A memory based on self-organized III-V quantum dots has the potential to realize such an ideal memory: in principle it is non-volatile and facilitates fast access times due to very fast carrier capture processes. The results of the first stage are very encouraging: the storage time was increased by nine orders of magnitude by altering the material system, fast write times in the order of nanoseconds were demonstrated, and fully functional prototypes were presented. The present second stage of the project aims at decisively advancing the concept of a quantum dot based memory. The focus is twofold:- First, novel heterostructures, including novel InGaAsSb/GaAlP quantum dots, are grown epitaxially. Their electronic properties and the hole storage time are determined. By the completion of the project, the hole storage time in the quantum dots is to be increased by at least two orders of magnitude as compared to the present situation. - The second goal of the project is the implementation of a novel quantum dot memory architecture, in which both charge carrier types are used to encode the information. The write and erase processes are then realized by selective injection of the complementary charge carrier into the quantum dots and subsequent optical recombination. This way the write and erase processes become independent of the capture and emission barriers. The present disadvantageous trade-off is lifted.