Theoretical investigation for the formation mechanism of CuAu-I type ordered structure in InGaAs/(110)InP alloy semiconductor using an empirical interatomic potential

It is known that a CuAu-I (L1(0)) type ordered structure is formed in an (I n, Ga)As alloy semiconductor grown on a slightly tilted (110)InP substrate. The energy gains due to the formation of L1(0) in a bulk alloy, in a thick epi-layer and in a single epi-layer on a two-monolayer step, were investig ated using an empirical interatomic potential calculation. It is confirmed that an L1(0) ordered structure is not stable in a bulk alloy. The ordered structure can exist stably in a thick epi-layer, but the energy gain due to the ordering is too small to form the ordered structure at the growth temp erature. The L1(0) ordered structure can actually form at a two-monolayer s tep on the growth-surface. This indicates that the atomic arrangement near the two-monolayer step has strong effects on the stability of the ordered s tructure in an (In, Ga)As alloy.