Amorphous boron nitride (aBN) has found broad applications in industrial applications. Thick aBN has been thoroughly investigated¹,², including the recent revisiting of this material at nanometer thickness. However, most investigations of aBN so far have been based on three-dimensional structures. In this thesis, Molecular-Beam Epitaxy (MBE) grown monolayer aBN in two-dimensional structure is demonstrated. In-situ gallium nitride (GaN) remote epitaxy is finished on the transparent monolayer aBN. By doing the in-situ remote epitaxy, contaminations are avoided, and epitaxial membrane quality is improved. Multi-stacking technique is developed to further enhance the manufacturing efficiency of the free-standing GaN film. Surface acoustic wave (SAW) strain sensor fabricated by free-standing ultrathin single crystalline GaN film shows good performances. Process to solve GaN device heat dissipation is presented. Relaxed InGaN film grown on aBN monolayer provides a new research direction for GaN based red LED.