Resistance switching memory characteristics of Si/CaF₂/CdF₂/CaF₂/Si resonant-tunneling quantum-well structures

Abstract

A novel resistance switching memory scheme using Si/CaF2/CdF2/CaF2/Si resonant-tunneling quantum-well (QW) structures grown on a Si substrate has been proposed, and write-read-erase cyclic memory operation has been demonstrated by applying pulsed input voltage sequences at room temperature. A resistance switching voltage of less than 1.0 V, a peak current density of 30–72 kA/cm2, and an ON/OFF ratio of 1.9–30 were observed. Under an appropriate bias condition, a retention time of more than 315 h and cyclic pulsed operation corresponding to write-read-erase-read for more than 4500 cycles were achieved.

Resistance switching memory characteristics of CaF2/Si/CaF2 resonant-tunneling quantum-well heterostructures sandwiched by nanocrystalline Si secondary barrier layers

“…A stable current response for the repeated input pulse of the memory cycle operation was observed for 28000 cycles with a current deviation ratio of 4.8% [= σ HRS =(μ LRS − μ HRS )], where σ HRS indicates the standard deviation of I HRS , and μ LRS and μ HRS indicate the mean values of I LRS and I HRS , respectively. A device with a similar potential profile using a CaF 2 =CdF 2 =CaF 2 resonant-tunneling QW structure exhibited 5000 pulsed operation cycles, 22) which strongly suggests the advantage for endurance and stability of the CaF 2 =CdF 2 =CaF 2 heterostructure. The device operation concept and configuration philosophy based on the band engineering of artificial nano-heterostructures proposed in this study are a possible candidate for new nonvolatile memories or a ReRAM scheme for future LSI technologies aimed at ultimate down scaling to the nanometer scale.…”

“…[17][18][19] Some of them utilize ion transport and electrochemical reactions to achieve the resistive state transition. To date, we have proposed and demonstrated a ReRAM cell using Si=CaF 2 =CdF 2 =CaF 2 =Si resonant-tunneling QW structures [20][21][22] grown on a Si substrate. This scheme has the potential advantages of a high-speed response, low power consumption, and ultimate scaling upon the appropriate design of electron transport and energy levels in QW structures by applying the concept of tunneling transport for the injection=ejection of electrons and charge traps in the QWs.…”

“…After loading into an ultrahigh-vacuum (UHV) chamber, nc-Si=CaF 2 = Si=CaF 2 =nc-Si multilayered structures were grown on the bottom Si by a molecular beam epitaxy (MBE)-based technique. 21,22,[27][28][29][30] The protective oxide layer was desorbed by Si flux at 750 °C in UHV. On the atomically cleaned Si surface, the first 2.2-nm-thick nc-Si layer was grown by codeposition using a Si molecular beam via electron-beam evaporation together with a partially ionized CaF 2 beam with an acceleration voltage of V a = 0.5 kV and an ionization current for an electron bombardment of I e = 350 mA to obtain an atomically flat nc-Si layer embedded in CaF 2 layers at a substrate temperature (T s ) of 80 °C.…”

Near-infrared (λ ∼ 1.2 μm) intersubband electroluminescence in Si/CaF2 quantum cascade structures

“…MBE was conducted to grow crystals. [31][32][33][34] Since it has been reported that the crystal growth of Si/CaF 2 thin films at around 80 °C suppresses the island growth of CaF 2 and improves planarity, crystal growth at around 80 °C was carried out for the i-Si and CaF 2 multilayer structure in this study. For CaF 2 deposition, ionization cluster beam deposition was carried out to improve the crystallity.…”

Analysis of single- and double-barrier tunneling diode structures using ultrathin CaF2/CdF2/Si multilayered heterostructures grown on Si

“…One essential building block for nanoscale solid-state devices is the electric potential sequences for controlling electron transport, which can be implemented using the energy band discontinuity at atomically abrupt heterointerfaces. A CaF 2 =CdF 2 =Si heterostructure is an attractive candidate structure for applications in Si substrates, such as resonant tunneling diodes (RTDs) 1,2) and transistors, 3) and resistance switching devices, 4,5) because of the large conduction band discontinuity (ΔE C ∼ 2.3 eV for Si=CaF 2 ) at the heterointerface 6) and the small lattice mismatch with silicon. To date, we have demonstrated high ON=OFF current ratios greater than 10 5 for CdF 2 =CaF 2 RTDs at room temperature (RT), 1,7,8) which confirmed the advantage of large-ΔE C heterostructure material systems.…”