Diode Schottky barrier

The decrease in free carriers (holes) after hydrogenation of p-type Si is also evidenced by the decrease in IR absorption at the longer wavelengths, where free-carrier absorption dominates, and by a decrease in the device capacitance of Schottky-barrier diodes, due to the increase in the depletion width (at a given reverse bias) as the effective acceptor concentration decreases. 

Fig. 4. Depth profiles of the donor concentration in Schottky-barrier diodes on n-type silicon (a) before and after hydrogenation (130°C, 60 min) and (b) after a post-hydrogenation anneal at 60°C with and without a reverse bias of 4 V (Zhu el at, 1990).

Fig. 10. DLTS spectrum for a Schottky-barrier diode on n-type ( 7 x 1015 P/cm3) silicon after hydrogenation (150°C, 50 min). The emission rate window e0 corresponds to delay times of 0.5 and 2.5 ms. Each peak is labeled with the measured activation energy for thermal emission of electrons (Johnson et al., 1987a).

Schottky Diode Growth. The electrical properties of the films deposited using SSP 1 (Fig. 6.13) were evaluated by current versus voltage (I-V) measurements recorded for the thin films using thermally evaporated aluminum contacts (10mm2), to make Schottky barrier diodes (see Fig. 6.14). 

Figure 5. Photograph of a point-contact Schottky-barrier diode. The magnification is about 11,000 times.

The ability to make ever smaller solid-state devices by improved lithography techniques has led to the development of so-called beam lead Schottky-barrier diode detectors and mixers in which diodes are fabricated by the same techniques used to make integrated circuits, and for this reason, they can be included in these circuits. Figure 7 shows such a beam-lead detector/mixer made by Virginia Diodes of Charlottesville, VA [15]. This same configuration is used in fabricating the varactor devices used for frequency multiplication discussed in the preceding section. 

More recently, Schottky-barrier diodes and backward diodes have been used as detectors. These do not require as much power to bias the diode to its optimum output and thus permit observation of EPR at lower incident power levels. They also have a much lower 1/f noise characteristic so that modulation frequencies between 6 and 25 kHz (equivalent to 200- to 900-pT sidebands) can yield the same sensitivity that 100 kHz provides with silicon diodes. 

The recombination current density, Jr, can be treated effectively as a Schottky barrier diode current density. Including both thermionic emission and diffusion charge transport mechanisms (13) Jr can be written as... 

Schottky-Barrier Diode and Metal-Oxide-Semiconductor Capacitor Gas Sensors Comparison and Performance... 

Schottky-barrier diode and metal-oxide-semiconductor (MOS) capacitor gas sensors have established themselves as extremely sensitive, versatile solid state sensors. 

PtSi arrays are sensitive over the 1.0-5.0 p,m wavelength range. These are silicon-based arrays in which the platinum-silicon junction in each pixel forms a Schottky barrier diode. Large, exceptionally uniform arrays can be made from this material, but the quantum efficiency is < 1% (D = 3 x 1010 cm I Iz0 5 W-1), making such arrays unsuitable for low light level applications. Photoconductive lead sulfide (PbS) arrays with 320 x 240 pixels are also available for operation in the 1.0-3.0 un range, with reported D values up to 3 x 1011 cm Hz0 5 W 1 if cooled to 200 K. 

Other groups have built tunable far-inffared spectrometers which do not involve high-frequency backward-wave oscillators. Verhoeve, Zwart, Versluis, Drabbels, ter Meulen, Meerts, Dymanus and McLay [61] have described a system in which fixed frequency far-inffared radiation is mixed with tunable microwave radiation in Schottky barrier diodes. This instrument has been operated up to 2.7 THz, and used to study OD and N2H+. A similar system, combined with a continuous supersonic jet, has been described by Cohen, Busarow, Laughlin, Blake, Havenith, Lee and Saykally [62], This instrument was used to study rare gas/water clusters. 

Walter Haus Schottky (1886-1976) received his doctorate in physics under Max Planck from the Humboldt University in Berlin in 1912. Although his thesis was on the special theory of relativity, Schottky spent his life s work in the area of semiconductor physics. He alternated between industrial and academic positions in Germany for several years. He was with Siemens AG until 1919 and the University of Wurzburg from 1920 to 1923. From 1923 to 1927, Schottky was professor of theoretical physics at the University of Rostock. He rejoined Siemens in 1927, where he finished out his career. Schottky s inventions include the ribbon microphone, the superheterodyne radio receiver, and the tetrode vacuum tube. In 1929, he published Thermodynamik, a book on the thermodynamics of solids. Schottky and Wagner studied the statistical thermodynamics of point defect formation. The cation/anion vacancy pair in ionic solids is named the Schottky defect. In 1938, he produced a barrier layer theory to explain the rectifying behavior of metal-semiconductor contacts. Metal-semiconductor diodes are now called Schottky barrier diodes. 

The lifetimes of the previous section depend on the concentration, capture cross-section and energy level of the impurities. Lifetime measurements, however, cannot easily be used for these determinations. DLTS is the technique most frequently used instead. It is based on the concept in Figure 5 (22). First consider the n-type Schottky barrier diode of Figure 5 (a) with no deep level impurities. A reverse bias -Vj creates a scr of width W. When the bias is reduced to zero, the scr is also reduced. The scr capacitance, being inversely proportional to W, is small and equal for cases A, C and D and large for case B. If the voltage is pulsed between zero and -V., the capacitance follows almost instantaneously and no time-dependent capacitance is observed. 

Currently, much work is devoted to the synthesis of conducting polymers for use in a variety of applications. Polyacetylene, the prototype conducting polymer, has been successfully demonstrated to be useful in constructing p-n heterojunctions, (1) Schottky barrier diodes, (2,3) liquid junction photoelectro-chemical solar cells, (4) and more recently as the active electrode in polymeric batteries. (5) Research on poly (p-phenylene) has demonstrated that this polymer can also be utilized in polymeric batteries. (6)... 

Schottky barrier diodes - a diode consisting of a metal-semiconductor contact which has rectifying characteristics similar to a p-n junction differs from a p-n junction diode in that the diode s forward voltage is different (lower for commonly used materials), and there is no charge stored when the diode is forward biased device can therefore be turned off very rapidly by application of reverse bias, as storage time is negligible. 

SiC p-n junction and Schottky barrier diodes C SCHOTTKY BARRIER DIODES... 

Both SiC p-n diodes and Schottky barrier diodes are utilized as UV photodetectors operating in the 200 nm to 450 nm range. They can be used up to temperatures of at least 700 K and are expected to be radiation tolerant. 

Schottky-barrier diode under high reverse bias. In this case, because the levels below midgap lie below J J and are always occupied, only the two deep levels above midgap at — 0.4 eV and — 0.6 eV will give rise to an ac charge distribution within the depletion region. The capacitance versus temperature curve for an assumed constant emission rate prefactor of v 10 ... 

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