Kinetic Engineering of Wurtzite and Zinc-Blende AlSb Shells on InAs Nanowires

Area of Science:

• Materials Science
• Nanotechnology
• Semiconductor Physics

Background:

• Heteroepitaxial growth of III-antimonides is crucial for advanced electronic and optoelectronic devices.
• Understanding crystal phase selection in nanowire shell growth is essential for controlling material properties.

Purpose of the Study:

• To investigate the selective heteroepitaxial radial growth of aluminum antimonide (AlSb) shells on InAs nanowire templates.
• To determine the influence of deposition parameters, particularly temperature, on the crystal phase and thickness of AlSb shells.
• To elucidate the underlying mechanisms governing the preferential growth of wurtzite (WZ) versus zinc-blende (ZB) AlSb.

Main Methods:

• Metal-organic vapor phase epitaxy (MOVPE) was used to deposit AlSb shells on InAs nanowire core templates with engineered axial WZ and ZB segments.
• Scanning electron microscopy (SEM), transmission electron microscopy (TEM), electron tomography, and energy-dispersive X-ray spectroscopy (EDX) were employed to analyze shell thickness, crystal phase, nanostructure, and composition.
• AlSb shell growth was studied as a function of shell growth temperature (Ts).

Main Results:

• WZ and ZB AlSb shells grew heteroepitaxially on corresponding WZ and ZB InAs core segments.
• Surprisingly, between 390 °C and 450 °C, WZ-AlSb shells were thicker than ZB-AlSb shells, with WZ thickness increasing as Ts decreased.
• ZB-AlSb shell thickness showed a slight increase with increasing Ts.
• Enhanced deposition on {112̅0} facets contributed to the increased thickness of WZ-AlSb shells.

Conclusions:

• Kinetic limitations in MOVPE of AlSb can lead to preferential growth of the WZ phase over the thermodynamically stable ZB phase at lower temperatures.
• The relative thickness of WZ and ZB AlSb segments can be tuned by controlling deposition parameters like temperature.
• These findings challenge previous assumptions about the favored growth of ZB-structured III-antimonides in heteroepitaxial radial growth.