NOVELTY - Fabricating a nanostructure (140) for antireflection involves: coating a solution containing a combination of metal ions with organic or inorganic ions on a substrate (100); sintering the coated solution using an annealing process to grow nanoscale metal particles; and chemically etching the substrate using the metal particles as a mask or accelerator to form the subwavelength nanostructure on the substrate.    USE - For fabricating a nanostructure for antireflection, which is integrated in a photo device (claimed), such as a solar cell, a photodetector, a light emitting device, or a transparent glass.    ADVANTAGE - The present method provides fabrication of the subwavelength nanostructure without an apparatus requiring a vacuum state using a simple method for a short amount of process time. Thus, reflection of light generated between a semiconductor material and the air may be minimized, and the nanostructure for antireflection is integrated in a photo device, to produce devices with good luminous efficiency and performance at low cost in large quantities. Even if a substrate has a step difference, a wafer-scale process is enabled. Also, a subwavelength nanostructure is fabricated on the substrate through a chemical etching process using metal particles having a controllable size. Thus, a nanostructure for antireflection having a low reflectance with respect to a wide wavelength range and a wide incident angle and a highly efficient photo device integrated with the nanostructure for antireflection is fabricated.    DETAILED DESCRIPTION - Fabricating a nanostructure (140) for antireflection involves: coating a solution containing a combination of metal ions with organic or inorganic ions on a substrate (100); sintering the coated solution using an annealing process to grow nanoscale metal particles; and chemically etching the substrate using the metal particles as a mask or accelerator to form the subwavelength nanostructure on the substrate. The metal is any metal capable of being bonded to the organic or inorganic ions in a solution state and being sintered such that the metal is separated from the organic or inorganic ions and bonded to other metals through annealing to grow subwavelength metal particles. The annealing of the coated solution is performed in a nitrogen (N2) atmosphere to prevent oxidation of the metal ions and improve reproducibility and reliability with respect to the size and thickness of the metal particles. When the metal ions are bonded to the organic ions, the combination is diluted with one alcohol-based solution selected from methanol, ethanol, and isopropyl alcohol to adjust the concentration of a metal, and when the metal ions are bonded to inorganic ions, the combination is diluted with water to adjust the concentration of the metal so that the solution is coated to a thickness of 1-500 nm. The chemical etching of the substrate is performed by controlling a mixture ratio of water, nitric acid (HNO3), and hydrogen fluoride (HF) to 20:1:4 or 20:4:1 or includes performing a primary etching process using water, HNO3 and HF mixed at a mixture ratio of 20:1:4 and performing a secondary etching process using water, HNO3 and HF mixed at a mixture ratio of 20:4:1. An INDEPENDENT CLAIM is included for fabricating a photo device integrated with a nanostructure for antireflection, when the photo device is a light emitting device, involving: sequentially stacking an n-type doped layer, an active layer and a p-type doped layer and coating a solution containing a combination of metal ions and organic or inorganic ions on a top surface of a light emitting unit of the p-type doped layer, sintering the coated solution using an annealing process to grow nanoscale metal particles, and chemically etching the top surface of the light emitting unit of the p-type doped layer using the metal particles as a mask or accelerator to form a subwavelength nanostructure for antireflection on the top surface of the light emitting unit of the p-type doped layer; and when the photo device is a light receiving device, involving: sequentially stacking a p-type doped layer, an active layer and an n-type doped layer and coating a solution containing a combination of metal ions and organic or inorganic ions on a top surface of a light receiving unit of the n-type doped layer, sintering the coating solution using an annealing process to grow nanoscale metal particles, and chemically etching the top surface of the light receiving unit of the n-type doped layer using the metal particles as a mask or accelerator to form a subwavelength nanostructure for antireflection on the top surface of the light receiving unit of the n-type doped layer, where the nanostructure being configured to taper upward.    DESCRIPTION OF DRAWING(S) - The figure shows cross-sectional view illustrating a method of fabricating a nanostructure for antireflection.    Semiconductor substrate (100)    Nanostructure (140)