Suppression of Leakage Current of CdF₂/CaF₂ Resonant Tunneling Diode Structures Grown on Si(100) Substrates by Nanoarea Local Epitaxy

Abstract

CdF2/CaF2 resonant tunneling diode (RTD) structures of 100 nm diameter were fabricated in SiO2 hole arrays formed on Si(100) substrates. RTD structures were grown by molecular beam epitaxy (MBE) in SiO2 hole arrays. After the growth of the initial CaF2 layer at a substrate temperature of 120 °C, in situ annealing at 500 °C was carried out to reduce the density of defects or pinholes in the barrier layer. In the measurement of current–voltage (I–V) characteristics, negative differential resistance (NDR) was clearly demonstrated at room temperature. The peak-to-valley current ratio (PVCR) was 106. The valley current was significantly suppressed. Results obtained here strongly indicates that the RTD structures proposed in this study are promising for high-quality NDR elements compatible with Si LSI technology based on Si(100) substrates.

Retention characteristics of resistance switching memory using Si/CaF₂/CdF₂ quantum-well structures

“…Due to the large ΔE C , leakage current is expected to be suppressed in low level even at room temperature and moreover, voltage for tunneling transport can be reduced by utilizing multi-quantum-well tunneling scheme such as resonant tunneling or sequential tunneling with appropriate design of quantum-well layer thickness sequences. Up to now, we have demonstrated large peak-to-valley current ratio (PVCR) of CdF 2 /CaF 2 RTDs larger than 10 5 at RT [3,4], which confirmed advantage of the large ΔE C heterostructure material systems. And moreover, we have proposed and demonstrated novel scheme of resistance switching diode or resistance random access memory (ReRAM) using Si/CaF 2 /CdF 2 /CaF 2 /Si quantum-well (QW) structure [5].…”

Switching voltage reduction of resistance switching memory using Si/CaF₂/CdF₂ quantum-well structures

“…Due to the large ΔE C , leakage current is expected to be suppressed in low level even at room temperature and moreover, voltage for tunneling transport can be reduced by utilizing multi-quantum-well tunneling scheme such as resonant tunneling or sequential tunneling with appropriate design of quantum-well layer thickness sequences. Up to now, we have demonstrated large peak-to-valley current ratio (PVCR) of CdF 2 /CaF 2 RTDs larger than 10 5 at RT [3,4], which confirmed advantage of the large ΔE C heterostructure material systems. And moreover, we have proposed and demonstrated novel scheme of resistance switching diode or resistance random access memory (ReRAM) using Si/CaF 2 /CdF 2 /CaF 2 /Si quantum-well (QW) structure [5].…”

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

“…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. To establish a design paradigm for tunneling devices using heterostructure materials, the modeling of electron transport and key material parameters, such as the conduction band discontinuity and effective masses for atomically thin layers, is essential for the design and optimization of device performance.…”