Tunnel diode generator

The principal elements in commercial TDS equipment are a tunnel diode generator of repetitive voltage pulses with rise time of ca. 30 ps at a rate of ca. 100 KHz, probe circuits for observation of these pulses and their reflections in a coaxial line, and sampling oscillo-... 

The simplest and most widely used model to explain the response of organic photovoltaic devices under illumination is a metal-insulaior-metal (MIM) tunnel diode [55] with asymmetrical work-function metal electrodes (see Fig. 15-10). In forward bias, holes from the high work-function metal and electrons from the low work-function metal are injected into the organic semiconductor thin film. Because of the asymmetry of the work-functions for the two different metals, forward bias currents are orders of magnitude larger than reverse bias currents at low voltages. The expansion of the current transport model described above to a carrier generation term was not taken into account until now. 

As demonstrated by Heath et al., application of the LB technique in conjunction with semiconductor nanoparticies may lead to the generation of tunnel diodes [60]. These devices consist of a monolayer of 3.8 nm CdSe nanocrystals and an insulating bilayer of eicosanoic acid, sandwiched between an Au and an Al electrode. Advanced spectroscopic techniques such as attenuated low-energy photoelectron spectroscopy were also applied to LB-derived multilayered nanostructured assemblies of differently sized CdS particles [61]. Recent examples of applications of the LB technique... 

In contrast to p-type electrodes, an n-type electrode is under reverse conditions in the anodic regime. This has several consequences for pore formation. Significant currents in a reverse biased Schottky diode are expected under breakdown conditions or if injected or photogenerated minority carriers can be collected. Breakdown at the pore tip due to tunneling generates mainly mesopores, while avalanche breakdown forms larger etch pits. Both cases are discussed in Chapter 8. Macropore formation by collection of minority carriers is understood in detail and a quantitative description is possible [Le9], which is in contrast to the pore formation mechanisms discussed so far. 

Due to the technological importance of metal-insulator-semiconductor (MIS) devices, understanding of the nature of their electrical characteristics such as current-voltage (1-V) and tunnel magnetoresistance (TMR) is of great interest. Unless intentionally fabricated, a silicon Schottky diode possesses a thin interfacial oxide layer between the metal and the semiconductor. Additionally, a density of interface states is always generated at the boundary between the semiconductor and insulator. 

This means that I must be determined by thermal generation processes, as in the classical Shockley diode, and not by tunneling or interface recombination processes which do not, in. general, depend on E. Thus, although their calculation is made for p/n homojunction solar cells, it applies equally well to p/n heterojunctions, MIS or SIS cells in which I depends exponentially on the energy gap of the photovoltaically active semiconductor. 

MOM diode Metal-metal oxide-metal electrons tunnel through a thin (of the order of angstroms) oxide layer and IR radiation generates voltage. Extremely fast (100 GHz) and uncooled... 

---