Near band-edge optical properties of cubic GaN with and without carbon doping
We report the results of studying the optical properties of cubic GaN thin films with photoluminescence and photoluminescence excitation spectroscopies. The films are deposited by plasma-assisted molecular beam epitaxy on GaAs (001) substrates, with and without intentional doping with carbon atoms (p-type doping). The evolution of the optical spectra of the C-doped samples is consistent with a picture in which carbon enters into N-vacancies at low concentrations, producing a marked improvement in the crystalline properties of the material. At higher concentrations it begins to form complexes, possibly due to interstitial occupation. The temperature dependence on the absorption edge of the doped material is also measured and is analyzed with standard theoretical models.
Photoreflectance studies of optical transitions in cubic GaN grown on GaAs(001) substrates
Abstract The optical properties of cubic GaN epitaxial layers were investigated by modulated photoreflectance (PR) and photoluminescence in the temperature interval from 5 to 300 K. The epilayers were grown on GaAs(0 0 1) substrates by molecular beam epitaxy using a nitrogen RF-activated plasma source. The PR spectra show a transition which is well fitted using the third-derivative functional form of the unperturbed dielectric function, which we interpret as band-to-band transition. Our results allow determination of the temperature dependence of the main gap of c-GaN and give insights into the residual strain in the film, as well as allow us to estimate the binding energy of the complex formed by an exciton bound to a neutral acceptor.
A photomodulated spectroscopy study of InxGa1−xAs/GaAs superlattices and quantum wells
We present here a detailed study of photomodulated transmission and reflectivity at room and liquid‐nitrogen temperatures of a series of In x Ga1−x As/GaAs superlattices and a single quantum well. Our samples span a variety of alloy compositions and quantum‐well widths. We compare the results of our measurements with the predictions of an envelope‐function calculation, which includes wave‐vector dependence of the minibands. This comparison allows identification of several spectral features unmistakably arising from miniband dispersion. Also, accurate determination is made of the band‐offset parameter, whose value is discussed in the context of those obtained by other authors.