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Integer or half monolayers of CdTe have been deposited, every 20 monolayers, in 120-monolayer wide ZnTe/(Zn,Mg)Te quantum wells, by molecular beam epitaxy or atomic layer epitaxy on nominal (001) surfaces of ZnTe substrates. Low-temperature direct and piezomodulated reflectivity as well as C.W. and time-resolved photoluminescence have been taken from these samples. By comparison of samples grown in slightly different ways, we conclude that fractional CdTe layers, separated by a few ZnTe monolayers, grown in a Zn-rich environment, tend to grow in an ordered way: successive CdTe islands are stacked in vertical columns separated by columnar ‘voids’ of pure ZnTe. This behavior is the opposite of the staggered lineup of ZnTe islands in CdTe–(Cd,Zn)Te quantum wells, grown on Cd-rich substrates, recently observed by similar experimental techniques. Both behaviors are tentatively explained in terms of the relative stiffnesses of the materials of the inserts and of the matrix. |
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