Schottky barrier diodes ideality factor

Unfortunately, the real situation with Schottky diodes is not so good as was presented in the previous section. A hint of such problems was provided in Equation 3.38 where a diode ideality factor appears. Theoretically, one can measure the work function of both the metal and the semiconductor using photoelectron spectroscopy and other techniques. From this and the work function of the metal, one should be able to estimate the Schottky barrier height. 

Figure 7.31 demonstrates the very good rectifying behavior of such a Pd Schottky diode on undoped ZnO thin film. The current density ratio determined for bias voltages of +0.6 V and -3V is about 104 as shown in the inset of Fig. 7.31. The ideality factor n is about 1.5. The temperature-dependent current-voltage (IV, see Fig. 7.31) and capacitance-voltage (CV) measurements from 210 to 300 K explain the reason for the slight deviation of the ideality factor from unity and the dependence of the reverse current on the reverse bias. The barrier heights of the diode of Fig. 7.31 jy and

The peak absorption coefficient of OCS, 10 m", occurs at 462 GHz. This is by no means, however, the optimum working frequency due to the non-ideal behaviour of most MMW detectors. Commercial Schottky barrier mixer diode detectors show a quadratic roll-off in sensitivity at frequencies >100 GHz. If this is factored into Equation 6.1, the peak sample sensitivity occurs around 300 GHz, and the response is so flat that even at 100 GHz it has only fallen off by a factor of two. What is common to both curves is the dramatic fall-off in sample sensitivity at frequencies <100 GHz, reinforcing the point that the band 26-40 GHz is ill suited to high-sensitivity analytical spectroscopy. 

Pandey et al. [983] described In/CP Schottky devices fabricated via thermal evaporation of In on chemically synthesized P(ANi), poly(o-anisidine) and poly(aniline-co-o-anisidine). In the case of die last copolymer, the rectification ratio, ideality factor and barrier height were found to be 300, 4.41 and 0.497 V respectively, while they were 60, 5.5 and 0.510 V for the P(ANi) device. Bantikassegn and Inganas described [984] a Schottky contact made from poly(3-(4-octylphenyl)-2,2 -bithiophene) (P(TOPT)) in its neutral and PF -doped states and Al metal as the sandwich structure ITO/P(TOPT)/Al. Rectification ratios for the neutral and doped CP were observed to be ca. 5 and 3 orders of magnitude respectively, with diode quality factors (n) being 1.2 and 4.2 respectively. Liu et al. [122] fabricated Schottky diodes from L-B films of poly(3-alkyl-thiophenes) doped with an... 

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