Tunnelling-based SRAM

This paper describes the use of low-current-density tunnelling devices to obtain dense low-power (sub-100 nW/bit) compound semiconductor static random access memory (SRAM); this cell power is over two orders of magnitude lower than the best previously demonstrated in III-V materials. This same circuit topology promises orders of magnitude reduction in static power dissipation for silicon memories, assuming a suitable Si-based negative differential resistance device, at sub-pA current levels, is developed. The concept of low-standby-power tunnelling-based SRAM (TSRAM) is presented in the context of a scaling theory for all memories and a comparison is given across technologies. Experimental results for a 50 nW TSRAM gain cell using ultralow current density (~1 A cm -2 ) resonant tunnelling diodes and low-leakage heterostructure field-effect transistors are discussed. We describe a one-transistor TSRAM cell, verify its operation, and discuss merits of TSRAM relative to other memory types. Silicon TSRAM standby power is projected to be lower than that of conventional-style silicon SRAM or DRAM.