High Indium Content InGaN Strain Relaxation

Light-emitting diode (LED) is the most popular light source in the modern world. Because LED owns higher efficiency and brightness compared with conventional light sources, it is widely used in the illumination and the display of numerous devices. Due to its tunable bandgap, indium gallium nitride (InGaN) has been used as the material to make blue and green LEDs. However, in order to decrease the band gap of InGaN, more indium has to be incorporated into the material, which leads to a high lattice mismatch between the InGaN layer and the GaN substrate. This mismatch causes the low quality of high indium content InGaN, which obstacles the approach to use InGaN as the base material for RGB (red, green and blue) pixels. Here, we propose a method to fabricate high quality LED based on InGaN with high indium content using remote epitaxy. Conventionally, when an epilayer is grown on the substrate using epitaxy methods such as molecular beam epitaxy (MBE) and metal organic chemical vapor deposition (MOCVD), the lattice structure of the epilayer always perfectly follows the lattice structure of the substrate. Therefore, the epitaxial InGaN layer is always strained on the substrate because they are connected by strong covalent bonds.<br/>Remote epitaxy provides a way to avoid this constraint. When a layer of 2D material is deposited prior to the epilayer, the epilayer grown on the top of the 2D material still follows the crystalline structure of the substrate under the influence of the penetrated potential field from the substrate. However, unlike normal epitaxy methods, the epilayer of remote epitaxy spontaneously relaxes due to the slippery surface of the 2D material. The Van der Waal force on the 2D material doesn’t limit the relaxation like the covalent bond. Therefore, high quality InGaN can be obtained with this method. we have demonstrated the remote epitaxy based on in-situ MBE grown amorphous boron nitride (aBN). By doing the in-situ remote epitaxy, contaminations are avoided, and epitaxial membrane quality is improved compared with the previous transferred graphene method. High quality single-crystalline GaN is obtained with this method. These results show that aBN can be a good candidate for the InGaN remote epitaxy and build the foundation for this work. By depositing InGaN on 2D/GaN substrate, the misfit strain can be relaxed from the beginning of the growth regardless of the indium composition. By avoiding the strain-relaxation process, most of the dislocations can be eliminated. Similarly, the relaxed film also helps alleviate the quantum-confined Stark effect.