“…Even though the mismatches of lattice constants and thermal expansion coefficients between GaAs and Ge are negligible, challenges remain in growing GaAs directly on Ge substrate [2], mainly due to the formation of anti-phase domains (APDs) when polar materials GaAs grown on nonpolar materials Ge [5,6], and the atomic interdiffusion near the GaAs/Ge interface [1,[7][8][9]. For the former, it has been well established that under proper growth conditions, the APDs can be eliminated by the adoption of off-cut Ge substrates [10][11][12][13][14][15]. For the later, Chia et al demonstrated that the interdiffusion could be effectively blocked by introducing an interlayer with high bonding energy such as Al x Ga 1Àx As [16,17].…”