Integration of GaN thin films to SiO2–Si(100) substrates by laser lift-off and wafer fusion method
A process methodology has been adopted to bond GaN thin films to Si(100) substrates using the combination of laser lift-off and direct wafer fusion. Using optimum excimer laser conditions, 2–10 μm of GaN is lifted-off from sapphire. The lifted-off thin film is cleared from gallium residual and then suitably treated in a hydrofluoric, nitric and acetic acid mixture to render the surface hydrophilic. This treatment provides van der Waals bonds to immediately contact bond with SiO2–Si(100) substrate at room temperature. The bonds are further strengthened by a high temperature annealing at 650 ∘C for 2 h. The structural and mechanical characteristics of the bonded structure reveal uniform and high quality bonding. The optical characteristics of the transferred bonded film on SiO2–Si(100) substrate exhibit similar properties to that of GaN on sapphire. In a similar manner, high-brightness blue LEDs were transferred from sapphire to SiO2–Si(100) substrate with no deterioration in the electrical and optical performance of the device.