### Abstract

Picosecond carrier dynamics of deep bandtail states (3.1 eV) in an unintentionally n-doped GaN epilayer at room temperature under high excitation densities (i.e., N _{0} = 1.0× 10 ^{19}- 1.1× 10 ^{20} cm ^{-3}) have been investigated with nondegenerate femtosecond pump-probe (267/400 nm) reflectance (Δ R/R _{0}). All Δ R/R _{0} traces possess a ∼2 ps buildup time that represents an overall time for the initial non-thermal carrier population to relax towards the continuum extremes and then into the probed tail states. We observe a saturation of Δ R/R _{0} initial (first 10 ps) recovery rate γ _{i} at a density of 5- 6×10 ^{19} cm ^{-3} close to the Mott transition threshold obtained from time-integrated PL measurements. Such a saturation phenomenon has been identified as the trap-bottleneck due to the bandtail states and deep traps. As N _{0} is further increased, γ _{i} accelerates due to the onset of Auger recombination as the trap-bottleneck becomes effective. The best fit by the Auger model for N _{0} in the range of the mid-10 ^{19}-10 ^{20} cm ^{-3} yields an Auger coefficient of C _{a}?∼ 5.0× 10 ^{-30} cm ^{6} s ^{-1}.

Original language | English |
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Pages (from-to) | 521-526 |

Number of pages | 6 |

Journal | Applied Physics B: Lasers and Optics |

Volume | 80 |

Issue number | 4-5 |

DOIs | |

State | Published - Apr 2005 |

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## Cite this

*Applied Physics B: Lasers and Optics*,

*80*(4-5), 521-526. https://doi.org/10.1007/s00340-005-1766-9