A compound includes indium element (In), gallium element (Ga), aluminum element (Al) and oxygen element (O), the compound having a triclinic crystal system with lattice constants being a=10.07±0.15 Å, b=10.45±0.15 Å, c=11.01±0.15 Å, α=111.70±0.50°, β=107.70±0.50° and γ=90.00±0.50°.