Recent Progress in Investigation of Luminescent and Electrical Phenomena from Semiconductor Cleavage
Measurements of luminescence from cleavage of a range of semiconductors in vacuum and in air, have shown that some overall generalisations are possible. In the cases of Si, Ge, GexSil-x of three different compositions, and GaAs and InP, a short duration light emission (20 microsec. or less) was found to occur on cleaving. This luminescence took place whether the cleavage was in air or high vacuum. It has been interpreted as originating from defect regions on the cleavage surfaces. Another emission which only occurs upon cleavage in vacuum, is associated with bulk band recombination of electrons excited by the cleavage process. This has a relatively long duration in the cases of the elemental semiconductors, attributed to their indirect band gaps. Its spectral distribution reveals that hot electrons are present. A surface state signal has also been detected from Si. Preliminary work on cleavage in ambients other than air appears to indicate a signal-shortening effect. Studies of electrical conduction across the crack during cleavage of Si show that voltage pulses up to about 400 mV are produced at cleavage, with currents up to about 5 mA being detected. This is explained in part as due to generation of a dipole moment on cleavage. Such a dipole can only occur if scission takes place on the three-bond plane and not on the single-bond plane. This has important consequences for surface structure models.
KeywordsDipole Moment Luminescence Signal Bond Rupture Cleavage Surface Bond Scission
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