Theoretical approach to the tunneling mechanoluminescence produced during cleavage of II-VI semiconductors

This paper describes the tunneling mechanoluminescence (ML) produced during fracture of II-VI semiconductors. The electric potential surrounding the charged dislocations bends, valence band and conduction band strongly and consequently, the electron centres float up in synchronism with the band bending as the dislocations core approaches starting distance from the dislocation core the process of electron tunneling from the centre into the conduction band becomes significant. Thus, a moving dislocation can transfer electrons form deep traps to the conduction band. These electrons subsequently recombine with the holes at impurity centres and give rise to luminescence, which is the characteristic of the centres. When a II-VI semiconductor is fractured or cleaved initially the mechanoluminescence (ML) intensity increases with time attains a peak value I m at the time t m corresponding to completion of the fracture of semiconductors. After the completion of fracture, the ML intensity decay with time, whereby the initial fast decay is controlled by the pinning time of dislocations and the subsequent slow decay is controlled by the lifetime of electrons in the shallow traps. In the ML produced during the fracture of II-VI semiconductors, both I m and IT increase directly with the area of the newly created surfaces of the crystals. The ML intensity of II-VI compounds decreases with temperature. Expressions are derived for the rise of ML intensity, and the total ML intensity. A good agreement is found between the theoretical and experimental results related to the ML produced during the cleavage of II-VI semiconductors.