Epitaxial GaN Nanorods via Catalytic Capillary Condensation

TL;DR

This paper presents a catalyst-free method for growing epitaxial GaN nanorods using capillary condensation during thin film deposition, revealing a new growth mechanism for controlled nano-structure fabrication.

Contribution

It introduces a novel catalytic process based on capillary condensation for epitaxial GaN nanorod growth without metal catalysts.

Findings

Nanorods grow from nanotrenches with epitaxial orientation.

Growth is driven by capillary condensation of Ga atoms.

Geometry constraints limit nanorod length.

Abstract

Intrinsic catalytic process by capillary condensation of Ga-atoms into nanotrenches, formed among impinging islands during the wurzite-GaN thin film deposition, is shown to be an effective path to growing GaN nanorods without metal catalysts. The nano-capillary brings within it a huge imbalance in equilibrium partial pressure of Ga relative to the growth ambient. GaN nanorods thus always grow out of a holding nanotrench and conform to the boundaries of surrounding islands. The nanorods are epitaxially orientated with <0001>GaN // <111>Si and <2110>GaN // <110>Si similar to the matrix. Concaved geometry is essential and is a condition that limits the axial dimension of the nanorods protruding above the base (matrix) material region. Revelation of the growth mechanism in the current context suggests that fabrication of nano quantum structures with controlled patterns is enabling for any attainable dimensions