Dynamics of free carrier absorption in InN layers

Carrier dynamics in highly excited InN epitaxial layers was investigated in the 1550–2440 nm (0.8–0.51 eV) spectral range by using a femtosecond differential transmission technique. A transition from induced bleaching to induced absorption was observed for probing energy of 90 meV below the bandgap of the samples. The decay of the induced free carrier absorption provided the averaged lifetime of the total nonequilibrium carriers. In the carrier density range of Δn=1018–1020 cm−3, the density-dependent recombination mechanism was attributed to trap-assisted Auger recombination with decay rate 1/τ=BTAARΔn, with BTAAR in the range (4–30)×10−10 cm3 s−1 for layers with different defect densities.