Interfaces random semiconductors

Veres et al. have shown that the field-effect mobilities of amorphous PTAA [18] and other polymers are higher in contact with low-k dielectrics with 8 < 3 than dielectrics with higher k [19]. The latter usually contain polar functional groups randomly oriented near the active interface, which is believed to increase the energetic disorder at the interface beyond what naturally occurs due to the structural disorder in the organic semiconductor film resulting in a lowering of the field-effect... 

When electrons move toward the interface, lattice sites from where electrons are originated become positively charged (Fig. 4b). Creation of positively charged carriers occurs randomly in the semiconductor (shown by a curved vertical line in Fig. 4b), but are situated not very far from the interface. Any mathematical treatment for such random distribution or even approximated exponential distribution of charged ions becomes a complicated system to deal with. 

What is the role of the constituents of the redox electrolyte present at the interface of the semiconductor-electrolyte junction Choice and optimization of the electrolyte has a substantial effect on PEC solar cells [18-19]. Before a semiconductor is immersed in an electrolyte, anions and cations freely and randomly move in the solution. As a result of this movement, no specific spatial accumulation of ions occurs in the solution. This situation alters... 

The inclusion of 2 extends the previously reported procedure of Relaxation Spectrum Analysis (44). in this form can include contributions from static disorder such as porosity (45), random mixture of conductor and insulator that can be described by the effective medium approximation at percolation (46), or an interface that can be described by a fractal geometry (47). It can also include contributions from dynamic disorder such as diffusion. To provide one specific example if originates from diffusion capacitance in the semiconductor, then r is the minority carriers diffusion time, n = 0.5 and... 

One remarkable example of a discontinuity-related effect is the interfacial spike in the conduction band edge, shown in Figure 3.22. The wider gap AlAs is doped n-type in this case. Enough electrons flow into the GaAs that near the heterojunction it is made so n-type that it becomes a metal. With careful design, this metallic layer can be rendered very thin such that the electrons find it very hard to move perpendicular to the heterojrmction. In other words, the potential traps them adjacent to the interface. Because they are free to move randomly in this plane and have a moderate to high concentration they are referred to as a two-dimensional electron gas. Because their motion is restricted, it is more difficult for them to scatter since they must remain in the interface plane. The consequence is that the electrons in the interface have a higher mobility than electrons in the bulk semiconductor. 

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