Hexagonal (2H) silicon (Si) semiconductors have excellent mechanical properties and optically diverse applications due to their structure and quasi-direct bandgap. The 2H-Si has a relatively lower direct band gap of approximately 1.69 eV at the Γ-point in comparison with that of diamond-silicon (i.e. 3.4 eV), but it is not actually a direct bandgap semiconductor. Herein, we report an optical property of wide spectrum light emission in visible and infrared ranges from grown Si crystals with a 2H structure of a 0 = 0.3824 nm, c 0 = 0.6257 nm, and c 0 /a 0 = 1.6362 corresponding to theoretical predictions and experimental results. Obtained via high-resolution transmission electron microscopy measurements, the crystal structure of the grown 2H Si possesses the only stable form of the 2H structure with the characteristic quasi-direct bandgap, achieved using mixed-source hydride vapor phase epitaxy at about 1200 • C. Raman, photoluminescence, and electroluminescence spectra, Commission International de l' Eclairage chromaticity coordinates of light emission, lattice parameters, and the quality of the crystals were evaluated and found to correspond with the predicted results. The reported material has potential applications in optoelectronics.

Although hexagonal (2H) silicon (Si) semiconductors exhibit excellent optical properties owing to their quasi-direct bandgap, their growth conditions, which require extremely high pressures, preclude their widespread use in industrial applications. The current study, therefore, proposes a novel approach for the facile growth of hexagonal Si at atmospheric pressure via a unique phenomenon known as Al-based nano absorber. A mixed-source hydride vapor phase (HVPE) method was used for the growth of the hexagonal Si single crystals employing a rapid interaction between GaCl3, AlCl, and SiCln gases at a high temperature of 1200 °C using a source mixture of Ga, Al, and Si. In this process, the Al-based nano absorber was formed, which resulted in the absorbance of Si atoms, rather than the growth of Al-based nano absorber, to form the Si crystals due to the subsequent lack of GaCl3 and AlCl sources. The hexagonal Si structure of these Si crystals was confirmed using scanning electron microscopy (FE-SEM), high-resolution X-ray diffraction (HR-XRD) spectroscopy, and Raman spectroscopy. Thus, the current study establishes atmospheric pressure mixed source HVPE as a facile approach for growing various allotropic crystals such as Si, C, or Ge via absorption of other atoms by an Al-based nano absorber.