Effect of V/III ratio on the structural and optical properties of self-catalysed GaAs nanowires

Abstract

The performance of GaAs nanowire (NW) devices depends critically on the presence of crystallographic defects in the NWs such as twinning planes and stacking faults, and considerable effort has been devoted to understanding and preventing the occurrence of these. For self-catalysed GaAs NWs grown by molecular beam epitaxy (MBE) in particular, there are in addition other types of defects that may be just as important for NW-based optoelectronic devices. These are the point defects such as the As vacancy and the Ga antisite occurring due to the inherently Ga-rich conditions of the self-catalysed growth. Here we demonstrate experimentally the effects of these point defects on the optical properties of GaAs/AlGaAs core-shell NWs grown by self-catalysed MBE. The present results enable insight into the role of the point defects both on their own and in conjunction with crystallographic planar defects.

Heterointerface‐Driven Band Alignment Engineering and its Impact on Macro‐Performance in Semiconductor Multilayer Nanostructures

“…The GPA results confirm the modulation of As-content in QWs on the epitaxial strain. The compressive strain in QWs shows a downward trend from ≈2.5% in A1 to ≈1.0% in A4 (Figure 4), in line with the high-resolution X-ray diffraction (HRXRD) Small 2019, 15,1900837 characterization (see Figure S6 and Note S3, Supporting Information). Obviously, A2 has obtained the most asymmetric strain distribution and followed by A3, attributed to the AlGaAs-like WoB interfaces and the "normal" BoW interface.…”

“…Based on the aforementioned two individual pieces of evidence from different perspectives, it suggests that the WoB interface Small 2019, 15,1900837 is As-rich to form the "AlGaAs-like" interface for the following reasons. First, the lattice constant of III-V alloys is expected to experience a sharp decrease with the increasing As-composition ( Figure S4a-c, Supporting Information).…”

“…Finally, when the compressive strain of InGaAsSb QWs decrease from A2 to A4, the WoB interface becomes less As-rich because the strain effect requires less tensile strain at interfaces to "neutralize" the compressive strain in QWs. A1 is a rather special case: despite that QWs are heavily strained, the QW material is actually As-free (InGaSb), which Small 2019, 15,1900837 means that the As-flux is off during the formation of the WoB interface, then A1 does not obtain the objective conditions for the interfacial As-enrichment. Traditionally, it is thought that the As-rich interface was associated with the degradation of crystalline quality, the creation of interfacial defects and the reduction of optical quality.…”

“…The rapid advance on molecular beam epitaxy (MBE) in the 1980s further prospered the design‐to‐order methodology . Since then, semiconductor quantum confined structures, with diverse dimensionalities and band structures, have experienced a booming development, including quantum dots, nanowires, quantum wells (QW), and superlattices …”

“…[12] The rapid advance on molecular beam epitaxy (MBE) in the 1980s further prospered the designto-order methodology. [1] Since then, semiconductor quantum confined structures, with diverse dimensionalities and band structures, have experienced a booming development, including quantum dots, [13,14] nanowires, [14][15][16] quantum wells (QW), [17,18] and superlattices. [5][6][7] Among all factors, with its inherent determination on actual band alignment, heterointerface is at the heart.…”