DISLOCATION FREE TECHNOLOGY FOR HIGHLY LATTICE MISMATCHED HETEROEPITAXY

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Growth technology of GaAs on Si substrate may open new area in opto-electronics. The present project aims at developing the technology to grow high quality GaAs on Si substrate. The technology developed in this project consists of two parts. In the first part, the technology for getting uniform GaAs by MBE on Si substrate was developed. To improve the crystal quality, various kinds of buffer layers were employed, for instance, GaAs buffer layer crystallized from amorphous GaAs thin layer, crystalline GaAs buffer layer epitaxially deposited at relatively low temperature, AlAs/GaAs double amorphous buffer layer and so on. The GaAs epitaxial layer is grown on these buffer layers with and without thermal cycle annealing. The evaluation of the GaAs layer was made by photoluminescence, by KOH etching and AFM. Among these buffer layers, A Among these buffer layers, AlAs/GaAs double amorphous buffer gave the best result. When the thermal cycle annealing was made during the GaAs EPITAXIAL GROWT … More H, films with low dislocation density of 3x10^6/cm^2, narrow X-ray FWHM of 145 sec and bright photoluminescence intensity were obtained.In the second part, epitaxial lateral over growth by LPE is employed to reduce the dislocation density. GaAs epitaxial layer grown by MBE on Si is used as a substrate and the surface is coated by SiO_2 film. Then narrow window of 5mum width is cut in the SiO_2 film and this part is used as a seed for the LPE growth. The growth is started from this window and when the height of the top surface exceeds the oxide layer the lateral growth starts. Since the oxide layer prevent the dislocation to continue the above layer, the part of laterally grown layer becomes dislocation free. This has been confirmed and drastic decrease of dislocation density in the laterally grown region was observed. However, relatively large number of stacking faults was observed. In conclusion, lateral epitaxial growth is very hopeful technique to get dislocation free GaAs on Si substrate. Less