Band Alignment Tuning in Twin-Plane Superlattices of Semiconductor Nanowires

Abstract

The band alignments of twin-plane superlattices in semiconductor nanowires are systematically investigated on the basis of density functional calculations. Our calculations demonstrate that for nanowires with small diameters the quantum-confinement effect is prominent within wurtzite structure regions and the energy gap in wurtzite-structured nanowires is remarkably larger than that including zinc-blende structure. This results in the straddling band alignment, in which both electrons and holes are confined in zinc-blende structure region. The analysis using a simple tight-binding methods also clarifies that the straddling band alignments can be realized when the diameters of nanowires are less than 4-8 nm, leading to full control of band alignments by varying the nanowire diameter. Our results provide the ability of band-alignment tuning and open new possibilities for band engineering.

Twin-induced one-dimensional homojunctions yield high quantum efficiency for solar hydrogen generation

“…However, the ordered structures can be broken when stacking faults are introduced. As a twin plane in ZB structure in the o1114 direction can be considered as a monolayer of WZ structure 25 , it means that a stacking fault in ZB (WZ) can create a segment of WZ (ZB). For example, in the ZB structure, misplacement of a bilayer to yield a sequence of AaBbCcAaCcBbAc results in a symmetry structure with a mirror plan Aa, which is known as a twin plane or twin boundary, whereas the consequent CcAaCc segment can be recognized as a three-bilayer WZ structure 28,35 .…”

“…Twinning in nanocrystals, especially in one-dimensional (1D) nanomaterials, has been investigated over III-V and II-VI semiconductors anticipating their potential applications in optical and electronic devices [24][25][26] . Usually, twin planes periodically occur with a constant spacing and have a long-range order, resulting in twinning superlattice (TSL) in a specific dimension [24][25][26][27][28][29] .…”

“…Usually, twin planes periodically occur with a constant spacing and have a long-range order, resulting in twinning superlattice (TSL) in a specific dimension [24][25][26][27][28][29] . Thus, mini-bands could be generated in this crystal structure 24 .…”

Linearly arranged polytypic CZTSSe nanocrystals

“…Therefore, the uncontrollable defect of random polytypism introduced in the synthesis stage would have some uncertain effects on the properties of the materials910. Recently, controlled polytypism and twinning engineering in one single III–V nanowire have been realized in vapor-liquid-solid (VLS) growth91011, and these engineered structure defects are expected to be useful in future optical, electronic and photovoltaic devices, as the variations in electron band structure of different polymorphs provide new possibilities to the band-gap tuning and alignment of semiconductor materials1213.…”

Evolution of morphology and microstructure of GaAs/GaSb nanowire heterostructures

“…However, the well-controlled synthesis of III-V NWs with a pure wurtzite (WZ) or zinc blende (ZB) phase can also bring about new application possibilities, since different crystal structures can lead to different band gaps [21][22][23] and, in turn, different electronic and optical properties. In fact, some novel structures like WZ/ZB or ZB twinning superlattice have been proposed [24][25][26][27]. However, antimonide NWs with the ZB structure are dominating from the previous reports, and this keeps true even for ternary antimonide NWs with only a small Sb concentration [28].…”