In situ passivation of Ga x In(1-x)P nanowires using radial Al y In(1-y)P shells grown by MOVPE

Ga x In(1-x)P nanowires with suitable bandgap (1.35-2.26 eV) ranging from the visible to near-infrared wavelength have great potential in optoelectronic applications. Due to the large surface-to-volume ratio of nanowires, the surface states become a pronounced factor affecting device performance. In this work, we performed a systematic study of Ga x In(1-x)P nanowires' surface passivation, utilizing Al y In(1-y)P shells grown in situ by using a metal-organic vapor phase epitaxy system. Time-resolved photoinduced luminescence and time-resolved THz spectroscopy measurements were performed to study the nanowires' carrier recombination processes. Compared to the bare Ga0.41In0.59P nanowires without shells, the hole and electron lifetime of the nanowires with the Al0.36In0.64P shells are found to be larger by 40 and 1.1 times, respectively, demonstrating effective surface passivation of trap states. When shells with higher Al composition were grown, both lifetimes of free holes and electrons decreased prominently. We attribute the acceleration of PL decay to an increase in the trap states' density due to the formation of defects, including the polycrystalline and oxidized amorphous areas in these samples. Furthermore, in a separate set of samples, we varied the shell thickness. We observed that a certain shell thickness of approximately similar to 20 nm is needed for efficient passivation of Ga0.31In0.69P nanowires. The photoconductivity of the sample with a shell thickness of 23 nm decays 10 times slower compared with that of the bare core nanowires. We concluded that both the hole and electron trapping and the overall charge recombination in Ga x In(1-x)P nanowires can be substantially passivated through growing an Al y In(1-y)P shell with appropriate Al composition and thickness. Therefore, we have developed an effective in situ surface passivation of Ga x In(1-x)P nanowires by use of Al y In(1-y)P shells, paving the way to high-performance Ga x In(1-x)P nanowires optoelectronic devices.