Diodes structure

In summary, the forte of SNMS is the measurement of accurate compositional depth profiles with high depth resolution through chemically complex thin-film structures. Current examples of systems amenable to SNMS are complex III-IV laser diode structures, semiconductor device metallizations, and magnetic read-write devices, as well as storage media. 

A.J. Campbell, D.D.C. Bradley, H. Antoniadis, M. Inbasekaran, W.W. Wu, and A.P. Woo, Transient and steady-state space-charge-limited currents in polyfluorene copolymer diode structures with ohmic hole injection contacts, Appl. Phys. Lett., 76 1734-1736, 2000. 

The wafers are processed into solar cells, the majority of which have a diode structure, as sketched in Figure 11.4, characterized by a thin, diffused, doped emitter, screen-printed front and back contacts and a front-surface antireflective coating. Prior to the effective cell manufacturing step, a chemical treatment of the silicon wafers removes... 

Fig. 10. Schematic of various LED and laser diode structures where EH signifies material of a lower energy band gap (a) homojunction, (b) double-heterojunction (DH), and (c) multiquantum well (MQW) structures.

Fig. 34. Schematic valence band diagram of resonant tunneling diode structures, simplified diagram of energy versus wave vector parallel to the interface, and resulting /-V curve by spin-splitting of the valence band of...

Temperature Effects. The general observation is that temperature enhances the speed of response of C-S and C-I-S diode structures to hydrogen as noted earlier. It also generally leads to a lower detection limit but also to a lower upper detection bound due to saturation of device response at lower ambient hydrogen concentrations. 

The maximum sensitivity to hydrogen decreases for diode structures at elevated operating temperatures. Many of these points are seen in Table III. 

In addition to the expected sensitivity to hydrogen, Table IV shows that the Pd/Si02/Si capacitor, unlike the corresponding diode structure, is also sensitive to CO in oxygen or air. However, as... 

We note from Table V that the diode structures, except for the TiOx-based I-layer diode at very low H2 ppm levels, tend to have lower sensitivities than the capacitors when looked at in terms of AV/V j. However, small changes in AVpg (or AVjjj in the MOSFET) must be electronically amplified to increase sensitivity. If the diode structures are operated in the AI/I y sensitivity mode, electronic amplification is generally not needed since AI is related to AAg through Equations 1 and 2. That is, when operated in the AI/I y mode, the device physics of the diode gives built-in amplification of small barrier changes as seen in Table II. 

As may be seen from Table I, the response times in hydrogen exposures of capacitor structures tend to be comparable to those of diode structures however, the capacitor structures can be susceptible to the HID phenomenon (16) especially at elevated temperatures. In general, the presence of water vapor or oxygen reduces the response and recovery times of both device classes. There are differences in gas sensing ability between the two structures. For example,. the Pd/TiOx/Si and Pd/SiOx/Si diodes do not respond to CO in... 

Figure 1. Diode structure and principles of operation of the silicon vidicon detector...

Prepared cathode samples were tested in a diode structure. The glass plate with sputtered ITO layer was used as an anode. The distance between anode and cathode was setting by glass spacers and equals 200 pm. During the experiment the pressure of residual gas in the vacuum chamber was less than 3 10 7 Torr. 

A more direct route to making polymer lasers would be to excite the polymers electrically in a diode structure. Although polymer LEDs have been made in which the injected carrier density matches the threshold excitation density of the best photopumped polymer lasers, a polymer diode laser has not yet been made. The threshold for diode lasers is higher because the electrodes that must be incorporated to the structure increase the waveguiding loss. In addition, for some... 

A variation of these configurations is to disperse the QDs into a blend of electron-and hole-conducting polymers (see Fig. 3.19c). This scheme is the inverse of light-emitting diode structures based on QDs (Colvin et al, 1994 Dabbousi et al, 1995 Schlamp et al, 1997 Mattoussi et al, 1998 Mattoussi et al, 1999). In the PV cell, each carrier-transporting polymer would have a selective electrical contact to remove the respective charge carriers. A critical factor for success is to prevent electron-hole recombination at the interfaces of the two polymer blends prevention of electron-hole recombination is also critical for the other QD configurations mentioned above. 

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