Electron holes, concentration

Germanium used for transistors has a resistivity of 2 cm and an electron hole concentration of 1.9 x 10 holes/cm. (a) What is the mobility of the electron holes in the germanium (b) What impurity element could be added to germanium to create electron holes ... 

When lithium oxide is dissolved in nickel oxide, monovalent lithium ions replace nickel ions. We obtain, therefore, an increase of the electron—hole concentration with increasing concentration of Li.O, The prime represents the negative charge of this impurity center Li> (Ni). 

We have seen that it is possible to control electron (and electron hole) concentrations by the chemical potential of a component of the crystalline compound within a finite range of homogeneity. This observation leads to an effect that is known as... 

Fig. 5. (a) Bulk electronic concentration at the metal—oxide interface and electron-hole concentration at the oxide—oxygen interface associated with equilibrium interfacial reactions, (b) Electronic energy-level diagram illustrating the dielectric (or semiconducting) nature of the oxide, with the possibility of electron transport (e.g. by tunneling or thermal emission) from the metal to fill O levels at the oxide—oxygen interface to create a potential difference, VM, across the oxide. 

The potential Vq (Fig. 7.17a) depends on electron-hole concentrations and is of the order of 0.5 V. If an external voltage V/, is applied with the positive pole... 

Thus if one solves explicitly for the cation vacancy concentration or the electron hole concentration. 

Since in the system investigated only the linear velocity changes, all other variables and constants are lumped together in K. Assuming now that the electronic conductivity of the scale is the limiting factor rather than the ionic one, the cathodic current can be set to be proportional to the electron hole concentration times the electron hole mobility ... 

The electrical conductivity is expected to vary proportionally to the electron-hole concentration and so with the sixth root of the oxygen partial pressure. A further possibility, however, is that a cation vacancy may bond with an electron hole, i.e., in NiO a Ni " " may be permanently attached to the Ni vacancy. In this case, the... 

This will produce lower interstitial anion concentrations with correspondingly reduced ionic conductivity, together with increased electron-hole concentration and associated increased electronic conductivity. 

Intrinsic and extrinsic defects do not play the same role. With the latter, impurities determine the electron (hole) concentration in the conduction (valence) band. A very important practical case occurs when non-stoichiometry depends on the atomic exchange between a crystal and the surrounding medium, usually gas. A simple binary non-stoichiometric compound for instance, is an intrinsic semiconductor or dielectric... 

All these defect concentrations depend on each other through the equilibrium constants. If an oxide has Schottky-type thermal disorder the vacancy concentrations are inversely proportional to each other through K. The electron and electron hole concentrations are interrelated through the formation equilibrium constant K,.. 

For MlECs of high disorder the concentration of mobile ions is large. It is assumed that the concentration of electrons and holes is small. The defect model is therefore denoted by p, n N . In this class fall the SEs. However, a number of dominantly electronic conductors may be found there as well. The reason is that a large electronic conductivity need not reflect a large electronic (electron/hole) concentration. When the mobility of the electron/hole is many orders of magnitude higher than that of the ions it is possible to And Oei Oj in spite of the fact that n, p N. ... 

Electrical conductivity for an intrinsic semiconductor-dependence on electron/hole concentrations and electron/hole mobilities... 

If za > Zb, then electron hole concentration decreases, Cg increases, and reactivity increases. 

If Za < Zb, then electron hole concentration increases, Cg decreases, and reactivity decreases. 

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