GROWTH OF II-VI BRAGG MIRRORS BY MOLECULAR-BEAM EPITAXY

Quarter wavelength distributed Bragg reflectors (DBRs) of MnZnSSe/ZnSS e (referred to as Mn-DBR) and MgZnSSe/ZnSSe (Mg-DBR) have been grown b y molecular beam epitaxy for the blue-green spectral region, In partic ular, a continuous in situ optical reflectance monitoring was employed to control the layer thickness of Mg-DBR. This growth monitoring tech nique appeared to be simple, low cost, accurate and extremely useful w hen preparing complex epitaxial layers which otherwise would require s table growth conditions for long time periods, The Mn-DBR consisted of a 25-pair stack of MnZnSSe and ZnSSe layers with the periodicity of 8 4.5 nm. The Mg-DBR consisted of a 20-pair stack of MgZnSSe and ZnSSe l ayers with a periodicity of 93.3 nm. All the structures were lattice-m atched to GaAs substrates. The Mn-DBR exhibited maximum reflectance of 81% centred at 486 nm at room temperature, while the Mg-DBR had maxim um reflectance of 86% at 473 nm, Experimental X-ray diffraction rockin g curves and computer simulated rocking curves for both the samples ex hibited sharp features in good agreement with each other and provided evidence that the constituent layers had grown coherently strained thr oughout the entire DBR structures.