Negative photoconductivity (NPC) and positive photoconductivity (PPC) are observed in the same individual InAs nanowires grown by metal–organic chemical vapor deposition. NPC displays under weak light illumination due to photoexcitation scattering centers charged with hot carrier in the native oxide layer. PPC is observed under high light intensity. Through removing the native oxide layer and passivating the nanowire with HfO2, we eliminate the NPC effect and realize intrinsic photoelectric response in InAs nanowire.Keywords: carrier scattering; InAs nanowire; intrinsic photoelectric response; NPC; PPC;

We report the first selective-area growth of high quality InAs(Sb)/GaSb core–shell nanowires on Si substrates using metal–organic chemical vapor deposition (MOCVD) without foreign catalysts. Transmission electron microscopy (TEM) analysis reveals that the overgrowth of the GaSb shell is highly uniform and coherent with the InAs(Sb) core without any misfit dislocations. To control the structural properties and reduce the planar defect density in the self-catalyzed InAs core nanowires, a trace amount of Sb was introduced during their growth. As the Sb content increases from 0 to 9.4%, the crystal structure of the nanowires changes from a mixed wurtzite (WZ)/zinc-blende (ZB) structure to a perfect ZB phase. Electrical measurements reveal that both the n-type InAsSb core and p-type GaSb shell can work as active carrier transport channels, and the transport type of core–shell nanowires can be tuned by the GaSb shell thickness and back-gate voltage. This study furthers our understanding of the Sb-induced crystal-phase control of nanowires. Furthermore, the high quality InAs(Sb)/GaSb core–shell nanowire arrays obtained here pave the foundation for the fabrication of the vertical nanowire-based devices on a large scale and for the study of fundamental quantum physics.Keywords: Core−shell nanowires; crystal structure; electrical properties; InAs(Sb)/GaSb; metal−organic chemical vapor deposition; selective-area growth;

We describe the controlled growth of planar InAsSb nanowires (NWs) on differently oriented Si substrates without any foreign catalysts. Interestingly, the planar InAsSb NWs grew along four criss-crossed ⟨110⟩ directions on an [100]-oriented substrate, two ⟨100⟩ directions plus four ⟨111⟩ directions on an [110]-oriented substrate, and six equivalent ⟨112⟩ directions on an [111]-oriented substrate, which correspond to the projections of ⟨111⟩ family crystal directions on the substrate planes. High-resolution transmission electron microscopy (HRTEM) reveals that the NWs experienced a transition from out-of-plane to in-plane growth at the early growth stage but still occurred on the {111} plane, which has the lowest surface energy among all the surfaces. Furthermore, the NWs exhibit a pure zinc-blende crystal structure without any defects. A growth model is presented to explain growth of the NWs. In addition, conductive atomic force microscopy shows that electrically rectifying p–n junctions form naturally between the planar InAsSb NWs and the p-type Si substrates. The results presented here could open up a new route way to fabricate highly integrated III–V nanodevices.

We present a study of Au-free InAsSb nanowire (NW) growth on Si (111) substrate under different growth parameters including V/III ratio, group Sb flow rate fraction (Sb-FRF, TMSb/(TMSb+AsH3)), and temperature. It was found that two different kinds of growth mechanisms for the Au-free InAsSb NW growth may be dominant depending on the growth parameters. At low V/III ratio and relatively high Sb-FRF, the NWs grow via vapor–liquid–solid (VLS) mode, while at high V/III ratio and relatively low Sb-FRF, they grow via vapor–solid (VS) mode. The NWs obtained by the two growth modes show clear differences in morphology, growth direction, and crystal quality. Under VS mode, the NWs exhibit unified growth direction and a uniform composition distribution, which are beneficial to integration devices of multiple NWs. On the other hand, under VLS mode, the NWs are first reported with pure crystal phase, which will be useful for the development of single NW devices.

This paper reports on significantly improved efficiency of InAs/GaAs quantum dot (QD) solar cells by directly doping Si into InAs QDs during the QD growth. The devices which contain five stacked QDs in their i-regions were grown using molecular beam epitaxy. It is shown that using appropriate Si-doing, the open-circuit voltage of the device can be increased to 0.84 V. This is dramatically higher than the value of 0.67 V obtained in undoped device using the same structure. Moreover, the efficiency of corresponding device is improved from 11.3% to 17.0%. This improvement in efficiency is attributed to greatly reduced energy loss in the devices that results from the reduction of the defect density in the stacked InAs/GaAs QD layers due to the doping.

•We demonstrated that InAs NWs on Si substrates are grown by self-catalyzed VLS mechanism.•We firstly achieved the growth of self-catalyzed InAs/GaSb axially heterostructured NWs, which can be used to fabricate p–n junction without Au contamination.•We realized the growth of InAs/GaSb core/shell heterostructured NWs by consuming In droplet on the top of InAs NWs.•We in detail discussed the reasons for the absence of In droplet in the growth of InAs NW.The growth mechanism of III–V nanowires (NWs) grown without the use of any foreign catalysts, especially the growth mechanism of InAs NWs grown on Si substrates, is still an open question and controversial. To make it clear, we in detail investigated metal–organic chemical vapor deposition (MOCVD) growth of InAs NWs on Si substrates. Based on assuming the growth of InAs NWs by self-catalyzed growth mode, we firstly realized the growth of InAs/GaSb heterostructured NWs both in the axial direction by utilizing the catalysis of In droplet and in the radial direction (core/shell structure) by consuming In droplet. In particular, we found the presence of a certain amount of In atoms in the top droplet of the InAs/GaSb axially heterostructured NWs, which is the direct evidence of self-catalyzed vapor–liquid–solid (VLS) growth mode for the growth of InAs NWs on Si. All the results obtained here support that the InAs NWs are grown by self-catalyzed VLS mechanism. The reasons for the absence of In droplets in the growth of InAs NWs were also discussed in details.

•As increasing nanohole size, many NWs per hole become thinner and thinner.•Well-defined and position-controlled NW arrays can be achieved.•SAG and strain-mediated growth regimes all exist in different size of holes.We have investigated the influence of nanohole size on selective-area growth (SAG) of InAs nanowire (NW) arrays on Si(111) substrates by metal-organic chemical vapor deposition. The growth of well-defined and position-controlled InAs NW arrays with united vertical orientation can be achieved on the patterned substrates with a certain range of nanohole size, which paves the way for the fabrication of high-electron-mobility and surrounding-gate transistor arrays using NWs as channels. Moreover, it is found that more than one NW are increasingly likely grown per nanohole as the nanohole size increases, and the NWs become increasingly thin and short. This is considered to be due to the supersaturation of adsorbed species in the nanohole and the intense competition for adatoms among multiple NWs per nanohole.