Role of Steps in GaAs Heteroepitaxial Growth on InAs(001) Surfaces

The role of steps during the initial stages of GaAs growth on InAs surfaces was investigated by scanning tunneling microscopy (STM). The surface structures of a nominally (001) InAs substrate and a misoriented (001) InAs substrate tilted by 1° towards the [111]B direction were observed by STM after a certain amount of GaAs deposition. In the case of a nominally (001) surface, a growth mode transition from two-dimensional (2D) to 3D island growth occurred when more than 0.75 ML GaAs was deposited. On the other hand, in the case of a vicinal surface, a growth mode transition did not occur when the same amount of GaAs was deposited onto the surface. In this case, GaAs-selective growth attached to the step edges and crack formation extending in the [11̄0] direction were observed in the STM images. These results indicate that the initial growth stages of GaAs heteroepitaxy on an InAs vicinal surface are different from those on a nominally (001) InAs surface due to the existence of steps.