Photoluminescence Properties of GaN Nanowires Grown in a Gradient-Plasma Environment

Abstract

Herein, we report the plasma effect on the surface defects of GaN nanowires (NWs). A gradient plasma growth system by microwave plasma chemical vapor deposition is demonstrated for NWs growth. The structure and surface defects of NWs are affected by the plasma distribution. The PL results show that emission peaks at ∼355, ∼374, and ∼389 nm arising from near band edge emission are observed from the GaN NWs under different plasma growth environment. The relative emission area (E relative) of the specific emission peaks to total emission area (E total) from the different growth regions also changes. The reason for variant ratio E relative /E total is related to the surface defects including structural defects and oxygen incorporation according to the results of high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy. The analysis of PL properties provided a strong evidence for formation of distinct surface defects. The emission mechanism of GaN NWs grown in a high-density plasma environment enriches our understanding of the plasma effects on the surface defects and optical property, and the knowledge is important to the development of nano-optoelectronic devices.

GaOx@GaN Nanowire Arrays on Flexible Graphite Paper with Tunable Persistent Photoconductivity

“…After the GaN NWs growth, self-annealing occurs in the environment with nonprotective gas and ample Ga 2 O decomposed from Ga 2 O 3 . In our previous study, there was no oxide decoration layer in the NW surface grown in a quartz reactor with a larger spiracle when cool down with a protective gas . The smaller spiracle is more conductive to source vapor circulation in the reaction process.…”

“…The growth rate increases with microwave power from 500 to 800 W. In contrast, both the top and bottom diameters of NWs decrease until the microwave power is 800 W. In our previous study of NW formation in a high-density plasma environment, growth is affected by diffusion and surface effects, which make the diameter of the top and bottom of the NW nonuniform. 36,37,44 The enhanced diffusion and impingement process affected by the plasma energy may provide an opportunity for aligned NW growth and more discussion can be found in Figure S3 in the Supporting Information.…”

“…53 In our previous study, there was no oxide decoration layer in the NW surface grown in a quartz reactor with a larger spiracle when cool down with a protective gas. 37 The smaller spiracle is more conductive to source vapor circulation in the reaction process. According to Lee et al's study, in ambient O 2 , GaN powders and vapor can easily be oxidized into Ga 2 O 3 .…”

“…The NWs are fabricated in a quartz reactor by MPCVD, as shown in Figure a. The shrinking spiracle and circular quartz boat make uniform and large-scale growth possible due to a steadier internal circulation process and prevention of direct etching by the plasma. , Meanwhile, the relatively steady circulation environment including decomposed Ga 2 O is conducive to the formation of an amorphous layer by self-annealing after the growth of GaN NWs. The photographs of the flexible GP wi.…”

“…In our previous study, GaN NWs were synthesized and modulated successfully by MPCVD. 37 The pure and high-quality GaN NWs were prepared in a quartz reactor with a bigger spiracle (Φ20 mm) under protection in a N 2 atmosphere in the cooling process. We designed and improved the quartz reactor to satisfy the demand for large-scale growth and better internal reaction circulation.…”