Epitaxial Deposition of GaAs in the Ga (CH,) ,-ASH, -H2 S y s tern (111) Heteroepitaxy on Isolating SubstratesEpitaxial growth of GaAs has been achieved on CaF,, a-Al,O, and spinel substrates. X-ray investigations showed well defined relations between layer perfection and the quality of substrate material. The formation of epitaxial layers in pyrolytic deposition processes is discussed in terms of supersaturation and its influence on nucleation and layer growth.Epitaktische Abscheidungen von GaAs wurden auf FluRspat-, Korund-und Spinellsubstraten erhalten. Rontgenuntersuchungen zeigten eine eindeutige Beziehung zwischen der Schichtperfektion und der Qualitat des Substratmaterials. Das Auftreten von Epitaxie bei pyrolytischen Verfahren wird durch eine Analyse der Ubersattigung und deren EinfluD auf Keimbildung und Wachstum diskutiert.
IntroductionWhereas reporting on the deposition of GaAs on GaAs and Ge in Part I and 11, here results of the deposition on completely substantially foreign materials shall be reported.Pyrolysis techniques for the first time enabled epitaxial deposition of GaAs on isolating substrates and until now solely resulted in reproducible effects (MANASEVIT 1968). I n Table 1 the already applied substrate materials and AIIIBv compounds ere listed, also considering other procedures, which, however, as a rule, did not lead to the formation of closed epitaxial intergrown films.The experiments were performed on mechanically polished surfaces of CaF, (hydrothermally grown by VEB Carl Zeiss Jena), spinel (MgO . 3 -3,5 A1,0,, Verneuil-grown by VEB Elektrochemisches Kombinat Bitterfeld) and on corundum (tempered Verneuil-crystals and platelets grown from PbF, flux, without additional surface treatment).Details of the used apparatus have already been described in Part I.The experiments were made to show the influence of the kind and quality of the substrate, the role of misfit and expansion coefficient on the crystallographic perfection of the expitaxial layers. Laue as well diffractograms were used for the characterizing of the layers.
Results
GaAs/CaF, hetero-layersEpitaxial depositions on (111) misoriented substrates (with a deviation of 10-15" from the exact lattice plane) were produced in the investigated temperature range about 700 "C. Due t o the large differences in the thermal expan-33 *