Dresden 2014 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 5: Nitrides: mostly transport properties and recombination processes
HL 5.6: Vortrag
Montag, 31. März 2014, 10:45–11:00, POT 251
Field-dependent photoluminescence of InAlN/GaN based HEMT structures — •Christoph Koch1, Martin Feneberg1, Rüdiger Goldhahn1, María Fátima Romero2, Fernando Calle2, Zhan Gao2, María Ángeles Pampillón3, Enrique San Andrés3, Pedro C. Feijoo3, and Pavel Y. Bokov4 — 1Otto-von-Guericke Universität, Magdeburg, Germany — 2Universidad Politécnica de Madrid, Madrid, Spain. — 3Universidad Complutense de Madrid, Madrid, Spain — 4Moscow State University, Moscow, Russia
The optical properties of InAlN/GaN based HEMT structures were examined by field-dependent photoluminescence spectroscopy as a function of temperature.
Samples grown on Si subtrate were investigated. On top of a thick GaN buffer layer, an InAlN barrier of 10 nm causes a two-dimensional electron gas (2DEG), which dominates PL spectra at low temperatures at energies slightly below the donor-bound exciton. Semi-transparent metal contacts were processed either directly on top of the structures or seperated by an additional high-k dielectric, serving as Schottky or MIS diodes, respectively. Free exciton recombinations of the GaN buffer were observed for higher temperatures and allow determination of the strain in the GaN layer. Due to sample structure PL measurements exhibit mostly GaN related features.
PL spectra with varying voltages and thus modified band diagrams were systematically studied. Consequently, a voltage-dependent shift of 2DEG related luminescence is observed, corroborating the assignment of this band to a 2DEG to free-hole transition.