Quantum confinement effects in variable band-gap GaN_xAs_1-x thin films studied by photoacoustic spectroscopy

By using the magnetron radio frequency (rf) sputtering deposition technique we have grown a new family of III–V nitride semiconductors: GaN_xAs_1-x thin films with nanocrystalline grain sizes and different N concentrations obtained by controlling the rf power used in the growth process. We have used the photoacoustic spectroscopy to measure the absorption edge behavior for the series of GaNAs films grown with different stoichiometries. The absorption spectra show a clear shift to higher energies as the N concentration increases; also, very remarkable shoulders in these spectra are clear evidence of the presence of optical transitions between energy levels produced by the quantum confinement effects that takes place because the average grain sizes (16 Å) are comparable to the exciton Bohr radius for GaN (28 Å). We discuss the quantum confinement regime for this case, and how information concerning the hole effective mass can be obtained by comparing a theoretical model to the experimentally observed transitions between the quantized electronic levels. © 2003 American Institute of Physics.