Deep bandtail states picosecond intensity-dependent carrier dynamics of GaN epilayer under high excitation

B. Guo, Z. R. Qiu, J. Y. Lin, H. X. Jiang, K. S. Wong

Research output: Contribution to journalArticle

6 Scopus citations

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 languageEnglish
Pages (from-to)521-526
Number of pages6
JournalApplied Physics B: Lasers and Optics
Volume80
Issue number4-5
DOIs
StatePublished - Apr 2005

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