Memory switching devices

A-Si H memory switches do not have counterparts in standard crystalline semiconductor technology, unlike the sensors, TFTs and LEDs. However, amorphous semiconductor switching devices have a 

The current-voltage characteristics of the device are shown in Fig. 10.14. The switching voltage is near 4 V, above which there is an abrupt change to a low resistance state. The ratio of the on- and off-resistances is more than 10 and varies with the geometry of the device, as discussed shortly. The device switches back to the high resistance states at a voltage of about — 1 V. 

The second characteristic of a memory device is filamentary conduction. Fig. 10.16 shows the on- and off-resistances as functions of the area of the device. The off-resistance scales inversely with area, as would be expected for a uniformly conducting material. The on- 

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Figure 8.19 1-V characteristics of (a) threshold and (b) memory switching devices.

S.-L. Lian, C.-L. Liu, W.-C. Chen, Conjugated Fluorene Based Rod-Coil Block Copolymers and Their PCBM Composites for Resistive Memory Switching Devices. ACS Appl. Mater. Interfaces 2011, 3,4504-4511. 

The closest parallel to the a-Si devices described in this paper seems to be the observation of memory switching in heterojunctions of n-type ZnSe grown epitaxially on p-type (single-crystal) Ge substrates, reported by Hovel (1970) and by Hovel and Urgell (1971). The ZnSe-Ge heterojunction devices are polar and the transition times for the OFF-ON and ON-OFF operation are both in the region of 100 nsec or less. Similar, but not so... 

Fig. 10.16. Dependence of the memory switch oif-resistance and on-resistance on device area, showing evidence of filamentary conduction in the on-state (LeComber et al. 1985).

Barium titanate (BaTiOj), a perovskite-type electro-ceramic material, has been extensively studied and utilized due to its dielectric and ferroelectric properties. The wide applications of barium titanates include multiplayer capacitors in electronic circuits, nonlinear resistors, thermal switches, passive memory storage devices, and transducers. In addition, barium titanate can be used for chemical sensors due to its surface sensivity to gas adsorption. 

The dynamic random access memory (DRAM) device, a two-element circuit, was invented by Dennard in 1967. The DRAM cell contains one MOSFET and one charge-storage capacitor. The MOSFET functions as a switch to charge or discharge the capacitor. Although a DRAM is volatile and consumes relatively high power, it is expected that DRAMs will continue to be the semiconductor memory of choice for nonportable electronic systems in the foreseeable future. ... 

State image sensors, charge-coupled devices, optical recording, visible light emitting diodes, fast modulators and detectors, hybrid structures, and memory switching. 

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