Positioned growth and spectroscopy of InP nanowires containing single InAsP quantum dots

We describe two different approaches to growing precisely positioned and diameter controlled InP nanowires on InP wafers. Both of these approaches utilize the selective area growth capabilities of Chemical Beam Epitaxy (CBE), one using the Au catalysed Vapour-Liquid-Solid (VLS) growth mode, the other being catalyst-free. In both cases a SiO₂ masked substrate is used with the nanowire positions determined through e-beam lithography. In VLS growth the nanowire diameter is controlled by the size of the Au particle, whereas when catalyst-free the diameter is that of the opening in the SiO₂ mask. The orientation of the nanowires is also different, <;111>;B when using Au particles and <;111>;A when catalyst- free. For the catalysed growth the effect of the Au particle can be turned off by modifying growth conditions allowing the nanowire to be clad, dramatically enhancing the optical emission from InAsP quantum dots grown inside the nanowire. Photoluminescence from individual InAsP quantum dots is observed, and it is shown that the s- to p-shell splitting can be reproducibly controlled through the nanowire diameter.