Direct experimental evidence for unusual effects of hydrogen on the electronic and vibrational properties ofGaNxP1−xalloys: A proof for a general property of dilute nitrides

Abstract

Direct experimental evidence for dramatic effects of hydrogen incorporation on the electronic structure and lattice properties of $\mathrm{Ga}{\mathrm{N}}_{x}{\mathrm{P}}_{1\ensuremath{-}x}$ alloys is presented. By employing photoluminescence excitation spectroscopy, postgrowth hydrogenation is shown to reopen the band gap of the GaNP alloys and to efficiently reduce the N-induced coupling between the conduction band states. By Raman spectroscopy, these effects are shown to be accompanied by hydrogen-induced breaking of the Ga-P bond in the alloy, evident from disappearance of the corresponding vibrational mode. According to the performed Raman and x-ray diffraction measurements, the hydrogenation is also found to cause a strong expansion of the GaNP lattice, which changes the sign of strain from tensile in the as-grown GaNP epilayers to compressive in the posthydrogenated structures, due to the formation of complexes between N and H.