The effects of annealing on the structural, optical, and vibrational properties of lattice-matched GaAsSbN∕GaAs grown by molecular beam epitaxy

Abstract

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.

Cathodoluminescence Characterization of Dilute Nitride GaNSbAs Alloys

“…Comparing the different samples, it can be noticed that the annealing process under As overpressure (insitu annealed sample) presents a higher redshift, getting closer to our 1 eV bandgap target, the lowest FWHM as well as the smallest energy bandgap shift along the growth direction. Our results are coherent with previous studies, where it was reported that the PL characteristics of the in-situ annealed samples (As atmosphere) were better than those of the ex-situ annealed samples [7,9,10]. The reason argued for this improvement was a more efficient elimination of N-related recombination centers [9,10], as well as a suppression of both N and As out-diffusion that leads to an improvement of Ga-N bonding [7].…”

“…The final authenticated version is available online at: https://doi.org/10.1007/s11664-018-6325-3 5 increment in the N content in the GaNSbAs layer due to the annealing process in N ambient [7], which would cause an As desorption and a N incorporation at such high temperature. Both hypotheses are coherent with the fact that the intensity of this low energy band increases closer to the surface.…”

“…This compound presents better thermal stability due to the fact that it contains just only one element of group III, and needs lower N concentration than GaInNAs to reach the same bandgap reduction [4]. As it happens with other dilute nitrides, post-growth annealing of GaNSbAs has been revealed beneficial to achieve a good quality material; however, the reason for this improvement is still not well understood [5][6][7][8][9][10]. Some authors have studied the effects of the thermal annealing by photoluminescence (PL) combined with high resolution X-ray diffraction (HRXRD) and secondary ion mass spectroscopy (SIMS) [7,9,10]; others have studied this effect by spectroscopic ellipsometry (SE) together with HRXRD and SIMS [8].…”

“…As it happens with other dilute nitrides, post-growth annealing of GaNSbAs has been revealed beneficial to achieve a good quality material; however, the reason for this improvement is still not well understood [5][6][7][8][9][10]. Some authors have studied the effects of the thermal annealing by photoluminescence (PL) combined with high resolution X-ray diffraction (HRXRD) and secondary ion mass spectroscopy (SIMS) [7,9,10]; others have studied this effect by spectroscopic ellipsometry (SE) together with HRXRD and SIMS [8]. Also, PL and photoreflectance spectroscopy (PR) [6] or PL together with HRXRD and transmission electron microscopy (TEM) have been used [5].…”

A Study of GaAsSb Nanowires by Molecular Beam Epitaxy for Near IR Applications

“…As shown in Figure 3.9, the variation in FWHM with temperature is less and T deloc is smaller in sample N2 due to the smaller range of values of the localization energies. In sample N1, the FWHM exhibits a small inverted S-curve, that is, a mild dip in the FWHM curve as the temperature approaches T deloc , which is a signature of strong exciton localization normally observed in dilute nitride system [39][40][41]. The T deloc is considerably larger for this sample.…”