Schottky diode contact

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). 

A piece of silicon immersed in an electrolyte behaves similarly to a Schottky diode, a metal-semiconductor contact, as discussed in Chapter 3. Under reverse... 

The development of SiC Schottky diode sensors was of interest due to their simple associated electronic circuitry. A Schottky diode usually consists of a metal contact on top of a low-doped semiconductor (Figure 2.6). These devices were pioneered by... 

Tobias et al. investigated Pt-gate 6H-SiC Schottky diodes with an interfacial layer of 1-nm Ta or 10-nm TaSq [78]. Both n-type and p-type diodes showed a gas response to hydrogen at 400-600°C. It was postulated that the gas response to hydrogen observed in the forward direction is mainly due to a change in the resistance of the gate contact. 

Another problem with Schottky diodes is that at high temperatures, the metal contact can anneal to the semiconductor, forming a silicide in the case of silicon and SiC [72, 80-83]. This can destroy the diode characteristic of the device, thus producing an unstable sensor. Use of an interfacial insulating layer, such as the oxide layer already mentioned, can prevent this from occurring. 

A mixed ion conductor, BaSnO, has also been tested as a contact layer on a Schottky sensor [90]. The BaSnOj/SiC sensor showed a response to oxygen and this was most pronounced at 400°C. The sensor was tested from 200°C to 700°C. Operated at 700°C, the sensor showed a negative resistance peak at a bias of 2V (Figure 2.8). This peak was accounted for by the tunneling or Esaki effect [91]. Up to an operation temperature of 400°C, thermionic emission was proposed to explain its behavior. At higher temperatures, a resistance connected in series with a Schottky diode can model the device [5, 73]. At temperatures of 500-600°C, the BaSn03 shows a mixed behavior of electronic and ion conduction, and the Nernst potential [92] can be added to the model. The complete proposed model is given in (2.9). 

Schottky diode sensors based on other wide bandgap materials have also been investigated, as previously mentioned. GaN Schottky diodes processed on either the Ga or N face have been examined by Schalwig et al. [11,21]. A Pt/GaN Schottky diode with a barrier height of 1-eV has been shown to reversibly transform into an ohmic contact through exposure to [94]. Kokobun et al. have also investigated Pt-GaN Schottky diodes as hydrogen sensors up to 600°C [15]. 

The SiC Schottky diodes and capacitors that have been processed by the authors were processed on either 6H or 4H substrates (n-type, about 1 x 10 cm ) with a 5-10- m n-type epilayer (2-6 x lO cm" ) [123, 124]. A thermal oxide was grown and holes were etched for the metal contacts. In the case of the Schottky sensors, the SiC surface was exposed to ozone for 10 minutes before deposition of the contact metal. This ozone treatment produces a native silicon dioxide of 10 1 A, as measured by ellipsometry [74, 75]. The MISiC-FET sensors (Figure 2.9) were processed on 4H-SiC, as previously described [125]. The catalytic metal contacts consisted of 10-nm TaSiyiOO-nm Pt, porous Pt, or porous Ir deposited by sputtering or by e-gun. 

UV-EL diodes were fabricated based on a Al/polysilane/ITO/glass structure.36 Glass or quartz plates coated with indium-tin-oxide (ITO) were used as substrates. The EL diodes operate at room temperature.36 A typical representation of the structure is shown in Figure 26.93 The device comprises a heterojunction forming a Schottky diode, with the polysilane film being the p-type layer, the ITO acting as an ohmic contact, and the A1 being the Schottky... 

Schottky barriers like those shown in Figure (a) present nonsymmetric current versus voltage curves, which in some cases show high rectification and for this reason find practical application in Schottky diodes, which are devices constructed having a Schottky contact. The shape and height of the Schottky barrier, in practical cases, depends on several preparation process parameters, like surface cleanness, surface treatment, presence of surface states, etc. See also -> flat-band potential. 

Schottky contact — Alternative denomination of metal-semiconductor contact presenting a Schottky barrier. Depending on metal - work function, semiconductor electron affinity, doping of the semiconductor, conditions of the surface of the semiconductor before contact preparation, and preparation process, Schottky contacts with high rectification can be prepared. Devices encor-porating such contacts behave like a diode and for this reason, are also denominated Schottky diodes, whose main features are the capability of high frequency operations and low forward-voltage drop. 

Schottky diodes Schottky contact Schottky effect Schottky barrier Schwabe, Kurt... 

We have also realized interdigital metal-semiconductor-metal (MSM) contacts. We found a strong increase of the current through the stmcture by illuminating it with UV-light. If the stability under reverse bias of regular Schottky diodes (see Fig. 7) is achieved for interdigital stmctures we are confident that MSM stmctures are well suited for the realization of solar-blind UV-detectors. 

The semiconductor/electrolyte contact has been extensively investigated since the 1970s. A recent review [32] and text books [33, 34] furnish details of the theory and applications of semiconductor electrodes. Below are given only some elements necessary for the discussion. Phenomenologically the liquid junction behaves more or less like a solid-state Schottky diode, with the electrolyte playing the role of the metal layer. 

Figure 12.10 Mott-Schottky plot of 1/C, as a function of potential referenced to the flat-band potential for a GaAs Schottky diode a) potential referenced to the Ohmic contact and b) potential referenced to a reference electrode located in the electrolyte according to the lUPAC convention for semiconductor electrodes. ...

Solution Orazem et al. and Jansen et al. described the impedance response for an n-type GoAs Schottky diode with temperature as a parameter. The system consisted of an n-GaAs single crystal with a Ti Schottky contact at one end and a Au, Ge, Ni Schottky contact at the eutectic composition at the other end. This material has been well characterized in the literature and, in particular, has a well-knozvn EL2 deep-level state that lies 0.83 to 0.85 eV below the conduction band edge. Experimental details are provided by Jansen et... 

State-of-the-art Schottky diodes operate up to 400°C [28] see FIGURE 5. The stability of the Schottky diodes limits the maximum temperature of operation of SiC MESFETs since SiC itself can withstand much higher temperatures. State-of-the-art ohmic contacts can operate at significantly higher temperatures than Schottky contacts. 

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