IMPERFECTIONS IN II-VI SEMICONDUCTOR LAYERS EPITAXIALLY GROWN BY ORGANOMETALLIC CHEMICAL VAPOR-DEPOSITION ON GAAS

II-VI semiconductor heteroepitaxial layers have been grown on (001) Ga As substrates by OMCVD, at temperatures of 365-degrees-C. The systems were CdTe/ZnTe/GaAs, where, in some cases, (CdHg)Te was grown on top o f CdTe. We have examined the interfaces by transmission electron micro scopy (TEM). The ZnTe/GaAs interface is abrupt and contains misfit dis locations. On the contrary, there is no TEM contrast at the ZnTe/CdTe interface. Threading dislocations can also be observed (CdHg)Te grown on top of CdTe contains a remarkably low dislocation density. This is due to the interdiffusion multilayer process used for their preparatio n, which consists to, first, deposit alternate HgTe/CdTe layers (misfi t approximately 0.3%). This initial strained superlattice eliminates d islocations. X-ray microanalysis and secondary ion mass spectrometry h ave been used to detect the presence of impurities in the layers. Arse nic and gallium were found in concentrations up to a few percent in II -VI semiconductors. Their presence is due to interdiffusion in the lat tice and along dislocations.