| Budget Amount *help |
¥2,100,000 (Direct Cost: ¥2,100,000)
Fiscal Year 1993: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 1992: ¥1,400,000 (Direct Cost: ¥1,400,000)
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| Research Abstract |
We have invented a novel methodology of non-contact Deep level transient spectroscopy (DLTS) in very high spatial resolution based on scanning tunneling microscopy (STM). An STM tip is used to detect the transitent of surface photo-voltage (SPV) induced at surfaces of semiconducting crystals. Theoretical considerations showed that under an appropriate condistion, the SPV-DLTS signal, defined by the ratio of the decay component of SPV to the total magnitude of the SPV,is proportional to the density of sub-surface deep centers that trap minority carriers on illumination, We have experimentally succeeded in measureing, for a plastically deformed n-GaAs, SPV-DLTS spectra matching those obtained by optical-DLTS.From comparison of a two-dimensional map of the SPV-DLTS signal, obtained at the spectral peak temperature, with the SPV signal distribution, we concluded that the image contrasts in the SPV-DLTS image represent the presence of minority carrier traps in the depletion layr beneath the surface. The spatial resolution reached the order of 10nm even in this preliminary expriment. If we solve the remaining technical problem of thermal drift of the STM tip during temperature scanning, the STM-DLTS will serve as a powerful tool not only for local assessment of micro-fabricated structures but also for studies of crystalline defects in semiconductors.
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