Berlin 2012 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 80: GaN: Preparation and Characterization V (mainly Cathodoluminescence)

HL 80.3: Vortrag

Donnerstag, 29. März 2012, 11:45–12:00, ER 270

Cathodoluminescence investigation of polarization field effects in InGaN MQWs with AlInGaN barriers — •Silvio Neugebauer, Sebastian Metzner, Frank Bertram, Jürgen Christen, Lars Groh, Jürgen Bläsing, Armin Dadgar, and Alois Krost — Institute of Experimental Physics, Otto-von-Guericke-University Magdeburg, Germany

The optical properties of In_0.25Ga_0.75N multiple quantum wells (MQWs) with quaternary AlInGaN barriers have been investigated using highly spatially, spectrally and time-resolved cathodoluminescence (CL) microscopy. The samples were grown on c-plane sapphire substrates by MOVPE using an optimized AlGaN/GaN template. The Indium and Aluminum content of the barriers were increased systematically starting with binary GaN towards matched polarization with respect to the InGaN quantum well. In time-resolved CL measurements, the polarization unmatched reference sample with GaN barriers exhibits a blue-shift of the QW emission wavelength during the onset of the e-beam excitation. The blue-shift clearly indicates the screening of polarization fields. In complete contrast, the polarization matched sample shows a red-shift during onset which indicates that relaxation of carriers into potential fluctuations is the dominant process of the recombination kinetics. During decay both samples consistently show a red-shift of the emission wavelength (field effects as well as potential fluctuations). The results clearly indicate drastically reduced polarization fields when using quaternary barriers.