Thermal activation energies for

The literature abounds with reports of thermal activation energies for shallow donors in GaN, obtained from Hall effect measurements over a range of temperatures, above and below room temperature, though their interpretation is rendered problematic by a number of complicating factors. At low temperatures there is clear evidence for impurity band conduction (see, for example, [31]) which severely limits the temperature range over which data may usefully be fitted to the standard equation for free carrier density n in terms of the donor density ND and compensating acceptor density NA ... 

For concentrated Bi compounds another model yields a similar temperature dependence, viz. mobile excitons with concentration nj and self-trapped excitons with concentration n and an energy difference AE, representing the thermal activation energy for exciton migration through the lattice. Unfortunately it is seldom checked whether the temperature dependence of the decay time in concentrated systems refers to an intrinsic property of an isolated luminescent centre or to an activation energy for migration. This, by the way, holds also for other compounds which have been discussed above. ... 

Experimental measurements can provide information about potential energy surfaces for unimolecular reactions. As shown by Tolman, Fowler, and Guggenheim (Steinfeld et al., 1989) the thermal activation energy for a chemical reaction is... 

In the final step, these bound charge-carrier pairs dissociate by thermal activation. The necessary thermal activation energy for this is = -Ucp = Ecp - E and is reduced by an applied electric field which is superposed onto the Coulomb potential, that is by the Stark effect (see Fig. 8.17). 

Thermal activation energy for bond scission Volume... 

Resistivities and thermal activation energies for polyvinylpyridine (PVP), phthalocyanines (PHTH) and mesophenyltetrabenzporphyrins (MTBP) are displayed in Table II. Table III exhibits the resistivities and activation energies for the phenothiazines (PH), chlorpromazine hydrochloride (CPZ.HCl), and ionenes (lo Br and loPHBr). 

---