Polar optical phonons

Similar expressions can be generated for holes simply by letting coc - — relaxation time xB needs justification, which will not be attempted here. Suffice it to say that this assumption is not bad for elastic scattering processes, which include most of the important mechanisms. A well-known exception is polar optical-phonon scattering, at temperatures below the Debye temperature (Putley, 1968, p. 138). We have further assumed here that t is independent of energy, although this condition will be relaxed later. 

The Dispersion of Long-Wave Polar Optical Phonons in Diatomic... 

Allakhverdiev K.R., Babaev S.S., Salaev E.Yu., Tagyev M.M. (1978) Angular behaviour of the polar optical phonons in A3B6 layered semiconductors. Phys. stat. sol. (b). 96(1), 177-182. 

Values for both the hole and electron mobilities and carrier densities in various SiC polytypes are listed. Ionized and neutral impurity, acoustic phonon, piezoelectric and polar optical phonon scattering mechanisms are all found in SiC. In general, mobilities have increased and carrier concentrations decreased with time, reflecting the improvement in crystal quality whether bulk or epitaxially-grown material is considered. 

One of the approaches to estimate the effects of scattering mechanisms is to consider carrier temperature increase due to a particular mechanism [340]. In narrow-bandgap materials for a temperature range between 200 K and room temperature the prevaihng mechanism is polar optical phonon scattering [13]. The increase of carrier temperature due to this mechanism is [341]... 

Figure 18 Temperature dependence of the electron mobility for 6H-SiC. The broken lines show the calculated values of the mobility determined by the impurity scattering by the piezophonon scattering Itpiez by polar optical phonon scattering (Xp i, and by acoustic phonon scattering The solid hne shows the values for the mobility determined by acoustic phonon and optical phonon scatterings, which is in...

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