Molecular beam epitaxy of AlGaN nanowires: source configuration and correlated material properties and device characteristics

Semiconductor nanowires have emerged as an appealing material platform for cutting-edge semiconductor devices. Behind the exciting progress of semiconductor nanowire devices is the advancement in the understanding of the nanowire synthesis process and mechanism. In this article, I will focus on the recent development in the molecular beam epitaxy (MBE) of semiconductor aluninum gallium nitride (AlGaN) nanowires. MBE has become an attractive tool for large-scale semiconductor nanowire devices, whereas AlGaN is a technologically important semiconductor material for short-wavelength photonics, as well as high-power and radio-frequency (RF) electronics. Different from epilayers wherein only a horizontal surface is involved in the epitaxy, the epitaxial growth of nanowires in general involves both horizontal and vertical surfaces. Such a unique geometry, coupled with different source configurations, greatly affects the growth kinetics, and consequently the material properties and device characteristics. In this regard, the general considerations of MBE chamber configuration for epilayers are discussed first as the basics to understand the nanowire growth. This is followed by the uniqueness of nanowires. In the end, the experimental results regarding to the correlation of source configuration to AlGaN nanowire properties and device characterics such as alloy composition, optical properties, and light emission are discussed. This article could provide useful insight for the development of AlGaN nanowire devices as well as other epitaxial semiconductor nanowire devices beyond AlGaN, especially when the chamber configuration is considered. This article could also shed new light on explaining some features in semiconductor nanowires.