Growth of GaNxAsyP1−x−y alloys on GaP(100) by gas-source molecular beam epitaxy

We report structural studies on the epitaxial growth of GaAs/GaNAs core-shell nanowires (NWs) on patterned Si (111) substrates by self-catalyzed selective area growth using Gas-Source Molecular Beam Epitaxy. Epitaxial growth conditions were obtained using a combination of dry and time-sensitive wet etching of the SiO2 growth mask and native SiO2 layer, respectively. We found that higher growth temperatures resulted in a higher yield for the epitaxial growth of patterned self-catalyzed GaAs NWs on Si with an optimal temperature of 690 °C. The GaNAs shell growth at 500 °C was found to be conformal and maintained an epitaxial and dislocation-free interface with both the Si substrate and the GaAs nanowire. The micro-photoluminescence (μ-PL) measurement at 6 K revealed two bands peaking at 1.45 and 1.17 eV, which could be emission from the GaAs core and GaNAs shell. Transmission electron microscopy showed the zincblende crystal structure of GaAs and GaAs/GaNAs core-shell NWs with minimal twinning near the base of the GaAs nanowires and at the tips of the GaAs/GaNAs core/shell nanowires. This study illustrates the feasibility of the epitaxial growth of patterned GaAs with dilute nitride shells on Si substrates, which would have potential for Si-friendly intermediate band solar cells and telecom emitters.

mentioning

confidence: 99%

Self-catalyzed core-shell GaAs/GaNAs nanowires grown on patterned Si (111) by gas-source molecular beam epitaxy

Liu

Yao

Chen

et al. 2017

“…29 This can be significantly suppressed by post-growth rapid thermal annealing (RTA). [30][31][32] In our work, all GaNP samples were treated by RTA at 750 C for 30 s in 95% N 2 and 5% H 2 forming gas ambient. This RTA condition was experimentally determined as the optimal condition providing the highest photoluminescence intensity-a higher intensity indicating lower non-radiative defects.…”

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confidence: 99%

Enhanced conversion efficiency in wide-bandgap GaNP solar cells

Sukrittanon

Liu

et al. 2015

In this work, we demonstrate ∼2.05 eV dilute nitride GaNP solar cells on GaP substrates for potential use as the top junction in dual-junction integrated cells on Si. By adding a small amount of N into indirect-bandgap GaP, GaNP has several extremely important attributes: a direct-bandgap that is also tunable, and easily attained lattice-match with Si. Our best GaNP solar cell ([N] ∼ 1.8%, Eg ∼ 2.05 eV) achieves an efficiency of 7.9%, even in the absence of a window layer. This GaNP solar cell's efficiency is 3× higher than the most efficient GaP solar cell to date and higher than other solar cells with similar direct bandgap (InGaP, GaAsP). Through a systematic study of the structural, electrical, and optical properties of the device, efficient broadband optical absorption and enhanced solar cell performance are demonstrated.

“…19 The P incorporation rate was calibrated by P-induced RHEED oscillations on a surface with excess Ga adatoms. 19 The substrate was then annealed for 30 s to form Ga seed droplets.…”

mentioning

confidence: 99%

“…19 The P incorporation rate was calibrated by P-induced RHEED oscillations on a surface with excess Ga adatoms. 19 The substrate was then annealed for 30 s to form Ga seed droplets. Growth started by opening the Ga shutter and injecting PH 3 through a hydride injector into the growth chamber to initiate growth of GaP nanowires.…”

mentioning

confidence: 99%

Growth and characterization of dilute nitride GaNxP1−x nanowires and GaNxP1−x/GaNyP1−y core/shell nanowires on Si (111) by gas source molecular beam epitaxy

Sukrittanon

Kuang

Dobrovolsky

et al. 2014

We have demonstrated self-catalyzed GaNxP1−x and GaNxP1−x/GaNyP1−y core/shell nanowire growth by gas-source molecular beam epitaxy. The growth window for GaNxP1−x nanowires was observed to be comparable to that of GaP nanowires (∼585 °C to ∼615 °C). Transmission electron microscopy showed a mixture of cubic zincblende phase and hexagonal wurtzite phase along the [111] growth direction in GaNxP1−x nanowires. A temperature-dependent photoluminescence (PL) study performed on GaNxP1−x/GaNyP1−y core/shell nanowires exhibited an S-shape dependence of the PL peaks. This suggests that at low temperature, the emission stems from N-related localized states below the conduction band edge in the shell, while at high temperature, the emission stems from band-to-band transition in the shell as well as recombination in the GaNxP1−x core.