Dresden 2006 – scientific programme
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HL: Halbleiterphysik
HL 36: Optical properties
HL 36.12: Talk
Wednesday, March 29, 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 XA (Ry=59meV; Eloc=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 XA 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.