Carrier emission

Thanks to the principle of detailed balance, an equivalent descriptor is the lifetime r0+ for carrier emission via the inverse reaction, i.e., for the... 

Unfortunately, no reliable estimate of cr is available for any hydrogen species. Since the hydrogen donor level seems to be somewhere near midgap, it is appropriate to recall the range covered by the cr values measured for various deep impurities in silicon (Milnes, 1973, Chapter 10), namely, cr 10-14 - 10 21 cm2. Such values would give r0 values in (22) of the order of microseconds to seconds at 200°C if eD = em. At room temperature, on the other hand, values as long as hours could occur if eD is well below em or o-+e is very small. The range of possibilities for other conceivable carrier emission processes (H°— H + h, H+— H° + h, etc.) is presumably similar. 

An equation analogous to (28) can also be written for the ratio n / ° in a depletion region. It would be conceivable for all three charge states, H+, H°, and H , to exist together in a depletion region, with steady-state concentrations having universal ratios dependent only on the four carrier emission rates. As we shall see in Section 4a in III, however, experiments suggest that H+ and H° have the major roles, with n+ a fraction of n0. The... 

Characterization of radiation-induced centers in the p -n-structures was carried out by means of deep level transient spectroscopy (DLTS) [3]. Concentrations, activation energies of charge carrier emission, and apparent capture cross sections of carriers were determined for all the traps observed. 

A more searching analysis of the Poole-Frenkel mechanism performed for polysiloxane on the basis of the Hill model ( ) showed that charge carrier emission should proceed from the isolated Coulomb centre and should take place in the hemisphere related to that centre. The depth of the centres, determined form the activation dependence of the temperature, was =... 

Mark and Gora [24], commenting on the results, considered a model in which initiation is associated with a critical interface field at the Schottky-barrier contact between the metal electrode and the azide. Interface fields depend on properties of the sample and on the work function of the electrode, and are larger than the applied voltage divided by sample thickness. The model predicted an effect for uniform samples which was qualitatively consistent with experiment, but whose magnitude was too small to observe. However, the experimental samples were pressed pellets composed of individual grains which are likely to be separated by potential barriers [25,26]. Taking this into account, the model was consistent with experiment if initiation occurs at a critical interface field of about 2 X 10 V/m. This is a plausible value, in that fields in excess of 10 -10 V/m applied to surfaces of wide band-gap semiconductors commonly result in destructive breakdown due to carrier emission into the bulk from interface states [27-29]. 

In general, the occupation of states in the gap is dominated by majority-and minority-carrier emission and majority-carrier capture. The emission rate for electrons at temperature T is usually given as... 

Given the electron and hole capture rates and t/(E), p in region B is readily computed and we can solve the dynamic barrier problem as in the voltage pulse case. The only additional complication for the calculation of experimental quantities arises for the case of current measurements. This is due to the fact that with minority-carrier emission present the change in the barrier charge need not involve the external circuit (see Cohen and Lang,... 

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