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FCA decay kinetics in different thickness HVPE GaN layers at various temperatures: (a) and (b) . Excitation fluencies were (a) and (b) .
Temperature dependences of (a) nonradiative lifetime and (b) ambipolar diffusion coefficient for different thickness GaN layers. Solid lines in (a) are calculated according to with , 5.29, and 0.98 cm for 145, 90, and layers, respectively. The lifetime increasing with layer thickness is described by dependence. In vs fit (b), and relations were used (, stand for ambipolar, hole, acoustic phonon, and polar optical phonon mobilities). In turn, and , where is the LO phonon energy, see Ref. 9. The dashed curve in (b) is a fit by a power function . The value at 300 K was found very close to the previously determined value of , see Ref. 10.
Dependence of nonradiative carrier lifetime on screw TD density in HVPE layers: points—experimental data and line—calculations according to Eq. (2). The dashed line is a power fit of the data . The inset shows the domain structure used for modeling [the hexagonal prisms are rotated by a small angle (Ref. 14), dots indicate the edge of inserted crystal plane, i.e., threading edge dislocations, TD]. The used value is approximately ten times lower than its theoretical limit at (Ref. 6), thus indicating that dislocations cover 10% of the grain boundary length , and the corresponding effective dislocation radius is of .
Layer thickness dependent dislocation density in HVPE grown GaN layers. Our data are compared with those from different sources.
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