Quantitative analysis of effect of dopant interaction on microstructural, physical, and electrical properties in laser-annealed SiGe:B:Ga film

Lowering the contact resistivity at the metal/semiconductor interface is a necessary requirement in the development of next-generation p-type metal-oxide-semiconductor logic devices. The contact resistivity can be lowered by B and Ga co-ion implantation followed by nanosecond laser annealing (NLA), a state-of-the-art annealing method, which can effectively incorporate dopants into the Si_1-xGe_x lattice, surpassing the solid solubility limit. When only the Ga-doped Si_1-xGe_x (SiGe:Ga) layer is used as a source/drain material, the electrical characteristics deteriorate in terms of bulk resistivity and device reliability owing to the graded Ga profile. However, it is possible to implement a uniform B profile in the B and Ga co-doped Si_1-xGe_x (SiGe:B:Ga) layer during NLA. In this study, we quantitatively investigated the effects of the B and Ga interactions on the microstructure, surface roughness, and lattice parameters of the laser-annealed SiGe:B:Ga films. We observed decreased defects on the surface and improved surface morphology after B co-doping; after analysis through reciprocal space mapping, we deduced that Ga had a higher contribution to the lattice parameter than B at the same B and Ga ion-implantation dose. Furthermore, by measuring the sheet resistance according to the type of dopant (B and Ga), we compared the electrical properties of the laser-annealed III-element-doped Si_1-xGe_x films with the B and Ga profiles after NLA. Our comprehensive study provides information on the behavior and interaction of B and Ga during NLA, thus presenting a path to understanding the physical and electrical properties of SiGe:B:Ga films.