Memory Cell for Data Storage – I

The most important factors for memories in any type of application are: fast read/write/erase times, storage density, endurance, reliability, and cost. DRAMs are fast and long endurance memories, but the data must be refreshed after latest 10 msec. Flash memories can store data for 10 years without refreshing, but are 1000 times slower than DRAM and show a bad endurance of about 1-10 million cycles.

The invention is a compound semiconductor quantum dot based non-volatile memory cell that combines the best of both DRAM and flash memory: large storage time with write speeds at least as fast as DRAM. One esssential difference to a normal flash memory is that by changing the bias on the depletion region, the QDs can be charged or discharged, equivalent to write or read processes. The energy levels of QDs are filled with a max of 2 carriers only. The QDs are located in the depletion region of the p-n junction of a specific heterostructure of type II, where only holes are stored in the QDs. Read/erase is achieved by using tunneling. The write mechanism is similar to that of a DRAM.