In this work we investigate the effects of ex situ annealing in N ambient and in situ annealing in As ambient on the temperature dependence of photoluminescence (PL) spectral characteristics of GaAsSbN∕GaAs single-quantum-well heterostructures. The focus of this work is on three representative nitride samples grown by molecular-beam epitaxy. The widths of the quantum wells (QWs) varied from 8 to 9 nm and the concentrations of nitrogen and antimony as determined from high-resolution x-ray diffraction and secondary-ion-mass spectroscopy were in the range of 0.8%–1.4% and 26%–33%, respectively. One sample was ex situ annealed in N ambient at 700 °C for 10 min. Two other samples were in situ annealed in As ambient at 650 and 700 °C, respectively, also for 10 min. Excitonic transitions in the QWs exhibit the well-known “S-curve” behavior in the temperature dependence of the PL peak energy. In addition, the variation of the full width at half maximum with temperature exhibits an “inverted S-curve” behavior. These are well-known signatures of localized excitons. The PL characteristics such as total integrated intensity and full width at half maximum as well as their temperature dependence, and the quality x-ray rocking curves clearly indicate that in situ annealing is more effective in reducing the densities of the localized states and of nonradiative recombination centers leading to better quality quantum well structures.
The structural, optical, and vibrational properties of a GaAsSbN epilayer lattice matched to GaAs with a band gap of 1eV have been investigated using a variety of characterization techniques. These layers have potential applications in GaAs based tandem solar cells that utilize the near infrared region of the solar spectrum. The epilayers were grown in an elemental solid source molecular beam epitaxy system with a rf plasma nitrogen source. The Sb and N compositions of the nearly lattice-matched layers are 6.8% and 2.6%, respectively, as determined by high resolution x-ray diffraction and secondary ion mass spectroscopy (SIMS) analysis. The high crystalline quality of the layers is attested by the presence of well resolved Pendellosung fringes on a triple axis (004) x-ray scan and dynamical truncation rods observed on the corresponding (004) reciprocal space map. The effects of in situ annealing in As ambient and ex situ annealing in N ambient on the low temperature photoluminescence (PL) characteristics are discussed. Ex situ (in situ) annealed samples display an 8K PL peak energy of 1eV with a full width at half maximum of 18meV (26meV). Raman spectral analysis, the temperature dependence of the PL peak energy, and SIMS profiles indicate that outdiffusions of N and As are suppressed in the in situ annealed samples and improvement in Ga–N bonding is observed, leading to higher PL intensities in these samples. In addition, indirect evidence of atomic scale ordering has been observed. The stability of these structures appears to be dependent on the annealing conditions.
In this work, the growth and characterization of GaAsSbN epilayers nearly lattice matched to GaAs, grown in an elemental solid source molecular beam epitaxy (MBE) system with a RF plasma nitrogen source, are discussed. The Sb and N compositions of the nearly lattice matched layers are 2.6% and 6.8%, respectively, as determined by high resolution x-ray diffraction (HRXRD) and secondary ion mass spectroscopy (SIMS) analysis. The layers are found to be fully strained as evidenced by the presence of Pendellosung fringes on the x-ray diffraction spectra.Effects of in-situ and ex-situ annealing on the low temperature photoluminescence (PL) characteristics are discussed. The 10 K PL peak energy of 1 eV with a FWHM of 18 meV has been achieved on ex-situ annealed samples in N ambient. The temperature dependence of PL peak energy exhibits “S-shaped” behavior in the low temperature regime, indicative of the presence of localized excitons. Raman spectroscopy analysis has been carried out to determine the local structural changes on annealing.
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