NUMERICAL-SIMULATION OF TRANSIENT EMISSION FROM DEEP-LEVEL TRAPS IN POLYSILICON THIN-FILM TRANSISTORS

Numerical simulation was used to model transient carrier emission from deep level traps in polycrystalline silicon (poly-Si) thin film trans istors and to validate the analytical approximations used to interpret DLTS measurements. Transient emission from a single trap was compared with that from a continuous density of states. Numerical simulation w as used to quantify the degree of error in the analytical analysis and show that it yields substantially correct values for a typical double exponential poly-Si trap state density as a function of energy, to wi thin +/- 10%. The major source of discrepancy was associated with the omission of the effects of displacement current from the analytical an alysis. The DLTS spectra associated with a constant density of states was shown to give a decreasing signal with decreasing temperature, whi le that of an exponential density of states was found to be essentiall y flat. (C) 1997 Elsevier Science Ltd.