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

半导体存储器的市场基本上分为两种存储器类型：一方面是快速但易失性的动态随机存取存储器(DRAM)，它需要周期性地刷新存储的信息，这一过程导致了大量的能量消耗。另一方面是非易失性闪存，即使在没有电源的情况下，它也可以存储信息10年以上，但存取时间慢，耐用性差。将DRAM和Flash各自的优势结合在一起，将产生一种具有快速访问和非易失性的理想存储器，被称为存储器的圣杯。基于自组织III-V量子点的存储器有可能实现这样的理想存储器：原则上它是非易失性的，并且由于非常快的载流子捕获过程而促进了快速访问时间。第一阶段的结果非常令人鼓舞：通过改变材料系统，存储时间增加了9个数量级，展示了纳秒量级的快速写入时间，并展示了全功能原型。该项目目前的第二阶段旨在果断地推进基于量子点的存储器的概念。首先，外延生长了包括新型InGaAsSb/GaAlP量子点在内的新型异质结。测定了它们的电学性质和空穴存储时间。到该项目完成时，量子点中的空穴存储时间将比目前增加至少两个数量级。-该项目的第二个目标是实施一种新的量子点存储器体系结构，其中使用两种类型的电荷载体来编码信息。然后，通过选择性地将互补载流子注入到量子点中以及随后的光学复合来实现写入和擦除过程。这样，写入和擦除过程变得独立于捕获和发射势垒。目前的不利取舍被取消了。

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.