Temperature dependence of characteristic parameters of the Au/SnO_2-Si (MIS) Schottky diodes

摘要

The variation in electrical characteristics of Au/SnO_2-Si (MIS) Schottky diodes have been systematically investigated as a function of temperature by using forward bias current-voltage (Ⅰ-Ⅴ) measurements. The main diode parameters, ideality factor n and zero-bias barrier height Φ_(B0), were found strongly temperature dependent and while the zero-bias barrier height Φ_(B0)(Ⅰ-Ⅴ) increases, the n decreases with increasing temperature. This behavior has been interpreted by the assumption of a Gaussian distribution of barrier heights due to barrier inhomogenities that prevail at the metal-semiconductor interface. The zero-bias barrier height Φ_(B0)vs q/(2kT) plot has been drawn to obtain evidence of a Gaussian distribution of the barrier heights, and values of Φ_(B0) = 1.101 eV and σ_0 = 0.158 V for the mean barrier height and zero-bias standard deviation have been obtained from this plot, respectively. Thus a modified ln(I_0/T~2) — (q~2σ_0~2)/2k~2T~2 vs q/(kT) plot has given mean barrier height Φ_(B0) and Richardson constant (A~*) as 1.116 eV and 127.86 A cm~(-2) K~(-2), respectively. The A~* value 127.86 A cm~(-2) K~(-2) obtained from this plot is in very close agreement with the theoretical value of 120 A cm~(-2) K~(-2)for n-type Si. Hence, it has been concluded that the temperature dependence of the forward bias Ⅰ-Ⅴ characteristics of the Au/SnO_2-Si (MIS) Schottky diode can be successfully explained on the basis of a thermionic emission (TE) mechanism with a Gaussian distribution of the Schottky barrier heights (SBHs). In addition, we have reported a modification by the inclusion of both n and αχ~(0.5)δ in the expression of I_0 to explain the positive temperature dependence of Φ_(B0) against that of energy band-gap of Si. Thus, the values of temperature coefficient of the effective barrier height Φ_(Bef)(-3.64 x 10~(-4)eV/K) is very close agreement with the temperature coefficient of Si band-gap (-4.73 x 10~(-4) eV/K).