A first example of the fabrication of large-scale diffractive microlens arrays on n-GaAs using an efficient electro-chemical technique named CELT (confined etchant layer technique) is reported. This microlens array is an eight-phase level diffractive optic device with eight concentric rings and seven steps in one lenslet. When appropriate chemical solutions and etching conditions are chosen, an approximate copy of the diffractive microlens array on the quartz is transferred onto the n-GaAs.