Dresden 2009 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 41: GaN: preparation and characterization II

HL 41.2: Vortrag

Donnerstag, 26. März 2009, 09:45–10:00, BEY 154

Spectrally and time resolved cathodoluminescence spectroscopy of AlN grown on sapphire by high-temperature MOVPE — •Martin von Kurnatowski¹, Barbara Bastek¹, Juergen Christen¹, Thomas Hempel¹, Outi Rentilä², Viola Küller², Frank Brunner², and Markus Weyers² — ¹Otto-von-Guericke-Universität Magdeburg — ²Ferdinand-Braun-Institut für Höchstfrequenztechnik Berlin

We present spectrally and ps-time resolved cathodoluminescence studies of AlN epilayers grown on sapphire by high-temperature MOVPE. The spatially averaged 5 K luminescence spectrum shows bright near band gap (NBG) emission dominated by a sharp (D⁰,X) peak at 5.94 eV. Apart from that, a broad luminescence band occurs at lower energies. It consists of two parts, centered at 3.0 eV and 3.8 eV, assigned to an O-DX-center and a Si defect, respectively. The intensity of the emission caused by Si-defects is characterized by a thermal activation, described by an activated Arrhenius-function. An activation energy of 48 meV is determined. Due to this behavior, the Silicon defects are interpreted as DX-centers as well.

For the analysis of the recombination kinetics and its temperature dependence periodic excitation was performed in ps-CL using rectangular e-beam pulses. Appropriately matched repetition frequencies ranging from MHz down to below 1 kHz and matched puls length were chosen, depending on the actual kinetics timescale. For the 3.0 eV band a strongly non-exponential decay is found with time constants ranging from the ns- to the ms-range.