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HL: Fachverband Halbleiterphysik
HL 51: GaN: preparation and characterization
HL 51.4: Talk
Friday, March 30, 2007, 11:45–12:00, H13
Luminescence properties of high quality non-polar a-plane GaN epilayers — •Martin Noltemeyer, Barbara Bastek, Lars Reißmann, Frank Bertram, Alexander Franke, Jürgen Christen, Matthias Wieneke, Armin Dadgar, and Alois Krost — Institute of Experimental Physics, Otto-von-Guericke-University Magdeburg, Germany
A set of high quality a-plane GaN layers is grown on r-plane sapphire-substrates by MOVPE and characterized by temperature (T) dependent photoluminescence (PL) and cathodoluminescence (CL). The T=4K PL spectra consist of several emission peaks: Near the band edge, a donor bound (D0, X) at 3.495 eV as well as an acceptor bound exciton (A0, X) at 3.482 eV can be resolved. Their spectral position corresponds to a compressive strain of 0.9 GPa. An emission at 3.30 eV originating from donor-acceptor-pair recombination (DAP) and accompanied by several LO-phonon replicas. A blue-shift of 34 meV is observed with increasing excitation density and with increasing temperature a high energy peak, i.e. the free-to-bound (e, A0) emerges. The dominating defect emission at 3.42 eV is attributed to excitons localized at stacking faults (SF) forming a wurtzite/cubic/wurtzite GaN quantum well. Temperature (T) dependent PL studies show a thermal quenching of the SF perfectly following an Arrhenius behavior with three activation energies (25 meV, 4 meV, and 40 meV). The SF peak energy shows an S-shaped T-dependence corresponding to a localization energy of 25 meV. Spatially resolved CL spectroscopy shows a homogeneous intensity distribution of the SF luminescence.