Long-Range Order inAlxGa1−xAs

Abstract

We report the first observation of long-range order in a semiconductor III-V ternary alloy. ${\mathrm{Al}}_x{\mathrm{Ga}}_{1-x}\mathrm{As}$ thin crystals grown by metal-organic chemical vapor deposition or molecular-beam epitaxy have Ga atoms preferentially occupying the 0,0,0 and ½,½,0 sites and Al atoms the ½,0,½ and 0,½,½ sites in each unit cell. Our results indicate that this ordered structure is the equilibrium state of ${\mathrm{Al}}_x{\mathrm{Ga}}_{1-x}\mathrm{As}$.