Presentation Information
[10a-A23-6]Effects of Porosity and Pore Depth in Porous Si Substrates on the Surface of
GaAs Thin Film Growth
〇Ryo Yoshitomi1, Momoko Sakuma1, Hidetoshi Suzuki1 (1.Miyazaki Univ.)
Keywords:
MBE,Porous Si,III-V
High-quality GaAs growth on Si substrates is expected to enable low-cost and high-efficiency solar cells, but stress caused by lattice and thermal expansion mismatches induces defects. In this study, porous Si(001) substrates with porosities ranging from 3 to 30% were fabricated by anodization and used for GaAs growth by molecular beam epitaxy (MBE). The influence of substrate porosity on strain relaxation and rotational twin formation during growth was investigated using reflection high-energy electron diffraction (RHEED), and the surface morphology after growth was examined by scanning electron microscopy (SEM). The GaAs thickness was fixed at 110 nm, and substrates with a pore depth of 200 nm were mainly studied. The surface lattice constant gradually changed from that of Si to that of GaAs with increasing film thickness, indicating strain relaxation during growth. Lower-porosity substrates achieved relaxation with thinner GaAs layers. The intensity of diffraction peaks originating from rotational twins decreased as growth proceeded, particularly within the initial 25 nm. However, rotational twins remained after growth on substrates with 30% porosity, whereas they were scarcely observed for 3% and 17% porosity. These results suggest that larger pores promote rotational twin formation and require thicker layers to achieve surface planarization and twin reduction. (992 characters)