Dresden 2006 – wissenschaftliches Programm

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HL: Halbleiterphysik

HL 36: Optical properties

HL 36.12: Vortrag

Mittwoch, 29. März 2006, 19:00–19:15, POT 151

Recombination kinetics of excitons in AlN — •Barbara Bastek¹, T. Riemann¹, J. Christen¹, K. Balakrishnan², N. Fujimoto², T. Kitano², M. Iwaya², S. Kamiyama², I. Akasaki², and H. Amano² — ¹Otto-von-Guericke-University Magdeburg, Germany — ²Meijo University, Nagoya, Japan

The luminescence of AlN layers is analyzed by spatially, spectrally and ps-time resolved cathodoluminescence microscopy (CL) at variable temperature. AlN was grown directly on 6H-SiC substrate by MOVPE above 1350^∘C. CL spectra at T=6K show bright near band edge emission (NBE) around 5.98eV and two broad defect related luminescence bands at 4.2eV and 3.2eV, respectively. The NBE peak position evidences tensile stress in the AlN layers and perfectly maps the stress relaxation at micro-cracks. The dominant NBE emission at 6K is assigned to an impurity bound exciton. At about 60K we observe the thermal activation of a high energy peak, identified as the free A-exciton X_A (Ry=59meV; E_loc=19meV). Periodic excitation of the AlN was performed in ps-CL by rectangular e-beam pulses. The NBE decay follows two different time scales (τ₁≈100ps, τ₂≈2.5ns). The slow component is preferentially found at the spectral position of X_A and vanishes at temperatures above T=15K. For the 3.2eV band a strongly non-exponential decay is found with time constants in the ms-range. The NBE recombination kinetics of different AlN layers is correlated with appearance and strength of the defect bands.