Doping conventional semiconductors

When an electron is added (by doping with donors or by photoexcitation) to the NDGS semiconductor polymer, it does not go into the conduction band as is the case in a conventional semiconductor. It deforms the polymer chain as shown in Fig. 2.4. The actual... 

Electronic Raman scattering originates not only from free electron excitations, but also from collective electron excitations in the form of plasmons. So far, these two types of excitation have been observed only in conventional semiconductors and to some extent in high temperature superconductors, as discussed in subsections 4.8.4 and 4.8.5. However, doped polymers with not too high carrier concentrations or charge transfer systems are possible candidates, and the search for electronic Raman scattering in such systems is one of the challenges in this held. 

Diamondlike Carbon and Hard Carbon-Based Sensors Sensors that are based upon diamond technology include thermistors, pressure and flow sensors, radiation detectors, and surface acoustic wave devices [103]. The relative ease of depositing prepattemed, dielectrically isolated insulating and. semiconducting (boron-doped p type) diamond films has made polycrystalline diamond-based sensors low-cost alternatives to those based on conventional semiconductors. Diamondlike carbon and diamond films synthesized by chemical... 

In hydrogenated amorphous silicon (a-Si H) mobility measurements are much more difficult to perform and to interpret for two reasons (1) the material has a disordered structure, and (2) undoped a-Si H is a photoconducting insulator whose transport properties have much in common with those of dielectrics. In many instances, even doped a-Si H may be very resistive compared with conventional semiconductors. Nevertheless, the Hall mobility can still yield valuable information about the bands involved in electron and hole transport. In this chapter some of the ideas that make the... 

Doping in a conventional semiconductor such as silicon is very different from that in a conjugated organic polymer. In conventional semiconductors, the dopant is a small amount of a donor or acceptor that is introduced into the atomic lattice resulting in a change in the occupancy... 

The general principle of operation of QCLs is depicted in Figure 4.19. Conventional semiconductor lasers (such as the diode lasers used CD-players and telecommunication applications and the lead-salt devices commonly used in the mid-lR) rely on electron-hole recombination across the doped... 

Another important feature to note regarding the bipolaron levels in particular is that they are either empty (p-type doping) or fiilly occupied (n-type doping), and thus spinless. An important reason why a model different from that of conventional semiconductors was sought for CPs is that in highly doped CP samples, which had high intrinsic conductivity, there was no evidence for unpaired electrons from experiments such as electron spin resonance (esr) measurements, or correlation of conductivity with esr absorption, but rather, spinless charge carriers were indicated [16]. 

Schematically show and compare the results of n-doping of a conventional semiconductor (e.g. Si with P) and a CP (e.g. poly(thiophene) with tetrafluo-roborate), using band structure diagrams, and molecular (for Si) and chain (for poly(thiophene)) structures. 

To a considerable extent, the recent interest in diamond is due to the fact that diamond can be doped. Substitutional boron forms an acceptor with an ionization energy of 360 meV [4] and phosphorus a donor with an ionization energy of 600 20 meV [11]. While these values are large compared to dopands in conventional semiconductors, they nevertheless make diamond a promising semiconductor with a considerable potential for power electronics and optoelectronic devices in the deep UV (5.5 eV = X = 225.8 nm). 

The most detailed NMR study of impurity band formation in a semiconductor in the intermediate regime involved 31P and 29 Si 7). line width and shift measurements at 8 T from 100-500 K for Si samples doped with P at levels between 4 x 1018 cm 3 and 8 x 1019 cm 3 [189], and an alternate simplified interpretation of these results in terms of an extended Korringa relation [185]. While the results and interpretation are too involved to discuss here, the important conclusion was that the conventional picture of P-doped Si at 300 K consisting of fully-ionized donors and carriers confined to extended conduction band states is inadequate. Instead, a complex of impurity bands survives in some form to doping levels as high as 1019 cm 3. A related example of an impurity NMR study of impurity bands is discussed in Sect. 3.8 for Ga-doped ZnO. 

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