Evidence and control of unintentional As-rich shells in GaAs_1–x P _x nanowires

Abstract

We report on the detailed composition of ternary GaAsP nanowires (NWs) grown using self-catalyzed vapor-liquid-solid (VLS) growth by molecular beam epitaxy (MBE). We evidence the formation of an unintentional shell, which enlarges by vapor-solid (VS) growth concurrently to the main VLS-grown core. The NW core and unintentional shell have typically different chemical compositions if no effort is made to adjust the growth conditions. The compositions can be made equal by changing the substrate temperature and P:As flux ratio in the vapor phase. In all cases, we still observe the existence of a P-rich interface between the GaAsP NW core and the unintentional shell, even if favorable growth conditions are used.

Computational Study of the Ene/Rearrangement Reaction between (F3C)2B═NMe2, 1, and Acetonitrile: Reactant-Catalyzed Mechanism of the Ketenimine–Nitrile-Like Rearrangement

“…While reaction self-catalysis is well established in biochemical − and polymer/materials processes, − it is rather rarer in organic synthesis , and rarer still in inorganic/organometallic synthesis. , The reaction studied here represents an intriguing example of aminoborane self-catalysis providing a functional group rearrangement. We plan to examine other pericyclic reactions in this area to see if other unusual reactions can be explained by self-catalysis.…”

Nanoscale electrical analyses of axial-junction GaAsP nanowires for solar cell applications

“…Figures 1(d) and (e) display the measured P and As concentration. The composition is homogenous along the NW axis; it is equal to GaAs 0.7 P 0.3 (we note that this value is measured on the NW sidewall, so it gives a compositional average over any eventual radial variations, which may appear in ternary NWs [43,44]). We conclude that in the MBE grown GaAsP NWs, the dopant (Be, Si) incorporation does not influence the crystal quality or NW composition.…”

Influence of surface passivation on the electrical properties of p–i–n GaAsP nanowires

“…17,18 One serious candidate for the top cell material in III-V/Si tandem devices is GaAsP. Several investigations of GaAsP NWs have been reported; 10,[19][20][21][22][23][24] however, the efficiency of GaAsP NW solar cells remains low. This is due to a more complex control over the optical and electrical properties of a ternary alloy and to a lack of knowledge of several fundamental parameters.…”

“…The GaAsP NWs were grown on patterned n-type Si (111) substrates by MBE following the previously optimized procedure. 24,29 Hexagonal arrays of nano-holes in a SiO 2 mask layer were defined by electron-beam lithography. The patterned substrates were outgassed in an ultra-high vacuum chamber at 450 C for one hour prior to the NW growth.…”

“…Indeed, structural and optical characterizations on undoped GaAsP NWs grown under similar conditions showed the formation of an unintentional GaAsP shell due to a parasitic lateral growth by the vapor-solid mechanism, which accompanies the axial NW growth. 23,24 This shell was shown to be optically inactive in bare NWs, but it produced luminescence in NWs passivated with a GaP shell. 23 In the present case of the p-i-n junction NWs, the unintentional shell formed around the base part during the deposition of the top pdoped segment is expected to be p-doped.…”