Study of low-frequency excess noise in GaN thin films deposited by RF-MBE on intermediate-temperature buffer layers

Low-frequency excess noise was measured in a series of GaN epitaxial films deposited by RF-plasma assisted molecular beam epitaxy (MBE). The GaN epitaxial layers were grown on double buffer layers, each consisting of an intermediate-temperature buffer layer (ITBL) deposited at 690°C and a conventional low-temperature buffer layer grown at 500°C. The Hooge parameters for the as-grown films were found to depend on the thickness of ITBL with a minimum value of 7.34 × 10 ^-2 for an optimal ITBL thickness of 800 nm. The observed improvements in the noise properties are attributed to the relaxation of residual strain within the material, leading to a corresponding reduction in crystalline defects.