Epitaxial Growth of Ferrite Films for Milliwave and Microwave on GaAs

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The establishment of epitaxial growth techniques between dissimilar materials is requisite to monolithic integrated devices for milliwave and microwave.In this project, we have studied on intermediate layr required for heteroepitaxially growing garnet ferrite films for microwave devices on semiconductor substrates and vice versa.As the intermediate layr, CeO_2 with the cubic fluorite crystal structure and Y_2O_3, In_2O_3 with the Sc_2O_3 type structure known to show epitaxy on Si and GaAs are promising candidates. We have revealed for the first time that these films are epitaxially grown in situ on (111)-oriented Gd_3Ga_5O_<12> garnet (GGG) substrates above 400ﾟC, 450ﾟC and 500ﾟC, respectively, by sputtering method. However, further epitaxy of Y_3Fe_5O_<12> garnet (YIG) films on these intermediate layrs formed on GGG has not yet been achieved. We have also sputter-deposited ZrO_2 films with the fluorite structure lower in crystal symmetry than that of CeO_2 as an intermediate layr. The ZrO_2 films (111)-oriented normal to the film plane were found to preferentially grow on (111) GGG substrates at 300ﾟCC - 400ﾟCC which is much lower than that of the films made by the evaporation method.We must further investigate the relationships between the epitaxy and the chemical bondings at the interface of the above dissimilar materials in details.