2021/06/23 by Hanno Küpers, Ryan B. Lewis, Küpers, Hanno +15 · 1 citation
Engineering · Physics and Astronomy · Materials Science · #Nanowire Synthesis and Applications #GaN-based semiconductor devices and materials #Quantum Dots Synthesis And Properties
paper · pdf · doi:10.48550/arxiv.2106.12309
Core-shell nanowire heterostructures form the basis for many innovative\ndevices. When compound nanowire shells are grown by directional deposition\ntechniques, the azimuthal position of the sources for the different\nconstituents in the growth reactor, substrate rotation, and nanowire\nself-shadowing inevitably lead to sequential deposition. Here, we uncover for\nIn0.15Ga0.85As/GaAs shell quantum wells grown by molecular beam\nepitaxy a drastic impact of this sequentiality on the luminescence efficiency.\nThe photoluminescence intensity of shell quantum wells grown with a flux\nsequence corresponding to migration enhanced epitaxy, i. e. when As and the\ngroup-III metals essentially do not impinge at the same time, is more than two\norders of magnitude higher than for shell quantum wells prepared with\nsubstantially overlapping fluxes. Transmission electron microscopy does not\nreveal any extended defects explaining this difference. Our analysis of\nphotoluminescence transients shows that co-deposition has two detrimental\nmicroscopic effects. First, a higher density of electrically active point\ndefects leads to internal electric fields reducing the electron-hole wave\nfunction overlap. Second, more point defects form that act as nonradiative\nrecombination centers. Our study demonstrates that the source arrangement of\nthe growth reactor, which is of mere technical relevance for planar structures,\ncan have drastic consequences for the materials properties of nanowire shells.\nWe expect that this finding holds also for other alloy nanowire shells.\n