ULTRARAM: Toward the Development of a III-V Semiconductor, Nonvolatile, Random Access Memory

ULTRARAM is a III-V compound semiconductor memory concept that exploits quantum resonant tunneling to achieve nonvolatility at extremely low switching energy per unit area. Prototype devices are fabricated in a 2\times2 memory array formation on GaAs substrates. The devices show 0/1 state contrast from program/erase (P/E) cycles with 2.5 V pulses of 500- \mu \text{s} duration, a remarkable switching speed for a 20~ \mu \text{m} gate length. Memory retention is tested for 8\times 10^{4} s, whereby the 0/1 states show adequate contrast throughout, whilst performing 8\times 10^{4} readout operations. Further reliability is demonstrated via program-read-erase-read endurance cycling for 10^{6} cycles with 0/1 contrast. A half-voltage array architecture proposed in our previous work is experimentally realized, with an outstandingly small disturb rate over 10^{5} half-voltage cycles.