Nanowires (NWs) have better functionality and superior performance as compared with the traditional thin film counterparts. However, NW growth is highly complicated and the growth mechanism is far from clear, especially when it is grown by vapor-liquid-solid mode. In this work, the influences of droplet size on the growth of self-catalyzed ternary NWs were studied using GaAsP NWs. The size-induced Gibbs−Thomson (GT) effect is observed for the first time in the self-catalyzed growth mode, which can make the smaller catalytic droplets have lower effective supersaturations. Thus, the droplet size can significantly influence the uniformity and composition of NWs. By carefully control the droplet size, the growth of highly uniform NW arrays are demonstrated. These results provide useful information for understanding the mechanisms of self-catalyzed III−V NW nucleation and growth with the important ternary III−V material systems.
Ternary GaAsP nanowires (NWs) have gained great attention due to their structure-induced novel properties and band gap that can cover the working wavelength from green to infrared. However, the growth and hence applications of selfcatalyzed GaAsP NWs are troubled by the difficulties in controlling P and the complexities in growing ternary NWs. In this work, self-catalyzed core-shell GaAsP NWs were successfully grown and demonstrated almost stacking-fault-free zinc blend crystal structure. By using these core-shell GaAsP NWs, single NW solar cells have been fabricated and a single NW world record efficiency of 10.2% has been achieved. Those NWs also demonstrated their potential application in water splitting. A wafer-scale solar-to-hydrogen conversion efficiency of 0.5% has been achieved despite the low surface coverage. These results open up new perspectives for integrating III−V nanowire photovoltaics on a silicon platform by using self-catalyzed GaAsP core−shell nanowires.
Self-catalyzed GaAsP nanowires (NWs) have a band gap that is capable of covering the working wavelengths from green to infrared. However, the difficulties in controlling P and the complexities of the growth of ternary NWs make it challenging to fabricate them. In this work, self-catalyzed GaAsP NWs were successfully grown on Si substrates by solid-source molecular beam epitaxy and demonstrated almost stacking fault free zinc blend crystal structure, Growth of high-quality shell has been realized on the core NWs. In the shell, a quasi-3-fold composition symmetry has been observed for the first time. Moreover, these growth techniques have been successfully applied for growth on patterned Si substrates after some creative modifications such as high-temperature substrate cleaning and Ga pre-deposition. These results open up new perspectives for integrating III−V nanowire photovoltaics and visible light emitters on the silicon platform using self-catalyzed GaAsP core−shell nanowires.
We realise growth of both GaAsP and GaAs core nanowires (NWs), as well as GaAsP core-shell NWs grown on (111) Si substrates using solid source molecular beam epitaxy (MBE). By modifying the growth conditions it is possible to change the dimensions of the GaAsP NWs and optimisation of these conditions yields high crystal quality structures. Scanning electron microscopy (SEM) as well as temperature, power and time resolved photoluminescence (PL) are used to study the optical and structural properties of the NWs. The incorporation of P into the NWs is used to shift the PL emission for ~ 810 nm to ~ 730 nm at 77 K, and also results in enhanced PL and an improved carrier lifetime. The addition of a p-doped GaAsP shell to a GaAsP core NW reduces the nonradiative recombination at surface states, as evidenced by x14 reduction of PL quenching with temperature, enhanced carrier lifetime, as well as a x3.5 increase in 77 K integrated PL intensity.