PROPERTIES AND STRUCTURE OF ANTIPHASE BOUNDARIES IN GAAS GE SOLAR-CELLS/

Antiphase boundaries (APBs) are particularly crystallographically simp le but technologically troublesome boundaries that tend to occur in pr ofusion in GaAs grown epitaxially on (100) oriented substrates of Ge o r Si. APBs were found to form only in a narrow band near the periphery of square wafers of GaAs/Ge grown by metal organic chemical vapour de position (MOCVD) to make solar cells for use on space satellites. Band s of APBs have continued to appear in a fraction of the wafers grown o ver a period of several years. The geometry of these bands is presente d and the distribution and structure of the APBs within it was studied by transmission electron microscopy (TEM) and scanning electron micro scopy (SEM) electron beam induced current (EBIC) and cathodoluminesenc e (CL). TEM showed that APBs and misfit dislocations were present in t he bands in earlier specimens while stacking faults were the only defe cts in areas outside the bands in more recent specimens. The significa nce of the formation of APBs only in a limited area and of their relat ively large interface recombination velocities are discussed.