Ultralow current density RTDs for tunneling-based SRAM

We report an improved tunneling-based SRAM (TSRAM) cell design using symmetric low current density InGaAs/InAlAs/AlAs/InAs resonant-tunneling diodes (RTD's). The new design eliminates an interconnect compared to the previous record low 50 nW TSRAM cell demonstrated with asymmetric low current density RTDs and heterostructure field-effect transistors (HFETs) in our InP-based integrated process. The simplified cell has 4/spl times/ smaller area than III-V FET-only SRAM cells at the same design rule. We also investigate experimentally and theoretically the mechanism for reduced peak-to-valley current ratios for very low current density (/spl sim/1 A/cm/sup 2/) RTDs which affects TSRAM cell standby power.