Role of ionized nitrogen species in the optical and structural properties of GaInNAs/GaAs quantum wells grown by plasma-assisted molecular beam epitaxy

Abstract

Internal quantum efficiency of III-nitride quantum dot superlattices grown by plasma-assisted molecular-beam epitaxy J. Appl. Phys. 109, 103501 (2011); 10.1063/1.3590151GaInNAs/GaAs quantum wells grown by molecular-beam epitaxy emitting above 1.5 μm Appl.We report on the impact of the nitrogen ion density on the structural and optical properties of GaInNAs quantum wells ͑QWs͒ grown by molecular beam epitaxy. The optical emission is strongly increased when the nitrogen ion density is reduced, as we found from photoluminescence experiments. Cathodoluminescence mappings of QWs grown under different ion densities are compared, showing a stronger modulation depth, and thus a higher structural disorder when a higher ion density was present during the growth. Atomic force microscopy measurements of equivalent epilayers showed that ions cause an important structural disorder of the layers. A nearly double root-mean-square roughness is observed when the density of ions is not reduced by external magnetic fields. Additionally, results of transmission electron microscopy measurements of buried GaInNAs QWs are presented, showing that lateral compositional fluctuations of In and N are suppressed when the QWs are protected from the ions. Finally, we find that QWs exposed to higher ion densities during the growth show deeper carrier localization levels and higher delocalization temperatures. These results provide clear evidence that the density of nitrogen ions present in the chamber during the epitaxial growth of GaInNAs QWs directly limits both the structural and optical properties.

Role of ion damage on unintentional Ca incorporation during the plasma-assisted molecular-beam epitaxy growth of dilute nitrides using N2∕Ar source gas mixtures

“…2͑b͒ utilized the ion deflector plates and was therefore grown without ions. Akin to a recent report by Miguel-Sanchez et al 33 that ions increase the surface roughness, it may also be possible that an increased surface roughness results from the more energetic atomic N species, which may be contributing to the higher Ca incorporation in the tail. 2͑a͒ and 2͑b͒, we see a Ca incorporation of ϳ10 16 cm −3 at the FIG.…”

Effects of different plasma species (atomic N, metastable N2*, and ions) on the optical properties of dilute nitride materials grown by plasma-assisted molecular-beam epitaxy

“…Samples at each of the three isonitrogen plasma operating combinations were grown with and without ions to measure the impact of ion damage. 15 As commonly cited, 24,25 ion removal led to optical improvement in all samples. Our previously reported ion energy distributions 26 show that the conditions which favor atomic N generation ͑i.e., high power and low flow rates͒ also leads to the greatest amount and energies of the ions.…”

“…This may happen either because atomic N has no strong dimer ͑N v N͒ to break, or because it is 3.6 eV more energetic than N 2 * , 28 and hence has more energy to hop to thermodynamically favorable lattice sites. A more favorable incorporation of atomic N can be responsible for the formation of compositional modulations of Gau N and Inu As at the edge of the QW, 25 in addition to promoting the creation of group III vacancies. 29 Upon annealing, a smoothening of these compositional modulations caused by the atomic N at QW interfaces may be leading to the more pronounced blueshift at the lower annealing temperatures shown in Fig.…”

Influence of arsenic flux on the annealing properties of GaInNAs quantum wells for long wavelength laser applications around 1.6μm

“…Since the first realization of laser diodes with emission wavelengths above 1.5 mm by Fischer et al [1], optimization of growth conditions and better understanding of the special characteristics of this material system has resulted in huge progress during the last years. Successful concepts include the use of GaAsN barrier material for strain compensation and wavelength extension [2], optimizing the growth temperature and corresponding As flux [3,4], adding Sb to the QW resulting in the quinary material GaInNAsSb [5][6][7], reduction of nitrogen plasmarelated defects (e.g., by the application of electric or magnetic fields to remove ions) [5,8]. Using these approaches, the realization of low threshold current laser diodes was possible allowing continuous-wave (cw) operation in the 1.5-1.6 mm range of both multi-mode [5,7,9] and single-mode devices [10,11].…”