Control of Polarity, Structure and Growth Direction in S n‐Seeded G a S b Nanowires

Abstract

Among III‐V semiconductor materials GaSb is highly interesting for several device applications such as optoelectronics. 1 The epitaxial growth of GaSb nanowires has mainly been done using Au as the seed material which demonstrated several limitations like direct nucleation and crystal structure tuning. 2 In this work we have investigated the epitaxial growth of Sn‐seeded GaSb nanowires directly nucleated on GaSb (111)A substrates with controlled Ga‐ and Sb‐polarities, and study their structural and physical properties. Nanowires are grown by metal organic vapor phase epitaxy (MOVPE) in a standard low pressure (100 mbar) horizontal MOVPE reactor (Aixtron 200/4). Sn‐seed particles are formed in‐situ by using Tetraethyltin (TESn) precursor at 530°C. Following the particle formation, the reactor temperature was changed to the nanowire growth temperature in the range of 490‐570°C. Trimethylgallium (TMGa) and trimethylantimony (TMSb) are used as precursors for nanowire growth. The polarity of the nanowires is confirmed by aberration‐corrected scanning transmission electron microscopy (STEM) as can be seen in Figure 1. It is shown that there are differences in the structural properties (i.e. growth direction, composition of the seed particle, and crystal purity) of Ga‐ and Sb‐polar nanowires; and their growth mechanism is studied. In addition, the formation of inclined twins which only occurs in the Sb‐polar nanowires is explained by using simulation methods. Also high‐angle annular dark‐field (HAADF‐) STEM image simulation is employed for realization of subtle features in the experimental images, as shown in Figure 2. In this Figure, presence of twin boundaries which is not perpendicular to the zone axis is proven. Finally, photoluminescence response of the Sn‐seeded GaSb nanowires is compared with their Au‐seeded counterpart, suggesting incorporation of Sn atoms from the seed particle into the nanowires. 3