Thickness-Induced Crystal Orientation Regulation in a Magnetron-Sputtered GaSb Buffer Layer for High-Performance InAs/GaSb Photodetectors

InAs/GaSb photodetectors (PDs) are of significant interest for high-performance infrared detection, driving the demand for low-cost fabrication of high-quality films. Here, we systematically investigate magnetron sputtering of the InAs/GaSb film and the effects of different growth parameters on the film structure and morphology. It was found that an elevated temperature facilitated Sb diffusion in GaSb thin films, leading to compositional stratification. Rapid thermal annealing at 600 °C significantly suppressed Sb diffusion, while spontaneous crystallization led to island-like growth on the film surface. Substrate-induced crystallization, controlled by sputtering time, suppressed spontaneous crystallization and produced a highly crystalline (100)-oriented GaSb film with a smooth surface. The InAs films deposited on the GaSb buffer layer demonstrate significantly enlarged grain size, collectively reducing nonradiative recombination centers. The fabricated InAs/GaSb PDs were tested at room temperature, demonstrating a dark current density of 1.1 × 10^-3 A/cm². Under 1310 and 1550 nm laser illumination, the device exhibited responsivities (<i>R</i>) of 1.32 and 3.46 A/W@-1 V, with corresponding specific detectivities (<i>D</i>*) of 7.04 × 10¹⁰ and 1.84 × 10¹¹ Jones, respectively. This work presents a promising approach for fabricating high-performance III-V heterojunction PDs at room temperature by using magnetron sputtering.