Inhomogeneous Schottky Contacts Research Articles

Barrier characteristics of [formula omitted] Schottky diodes as determined from I- V- T measurements

The current-voltage-temperature characteristics of PtSi/p-Si Schottky barrier diodes were measured in the temperature range 60–115 K. Deviation of the ideality factor from unity below 80 K may be modelled using the so-called T 0 parameter with T 0 = 18 K. It is also shown that the curvature in the Richardson plots may be remedied by using the flatband rather than the zero-bias saturation current density. Physically, the departure from ideality is interpreted in terms of an inhomogeneous Schottky contact. Here we determine a mean barrier height at T = 0 K, ƒ b 0 = 223 mV , with an (assumed) Gaussian distribution of standard deviation σ ƒ = 12.5 mV . These data are correlated with the zero-bias barrier height, ƒ j 0 = 192 mV (at T = 90 K), the photoresponse barrier height, ƒ ph = 205 mV , and the flatband barrier height, ƒ fb = 214 mV . Finally, the temperature coefficient of the flatband barrier was found to be −0.121 mVK −1, which is approximately equal to 1 2 (dE g i/dT) , thus suggesting that the Fermi level at the interface is pinned to the middle of the band gap.

The Ideality of Spatially Inhomogeneous Schottky Contacts

ABSTRACTWe present a new analytical theory of electronic transport for inhomogeneous Schottky contacts. Our model combines a novel method to solve Poisson's equation for the space charge region of an inhomogeneous contact with thermionic emission theory. We explain quantitatively the temperature and voltage dependences of the ideality factor n of current/voltage characteristics, and we are able to extract from experimental data information on the characteristic size of the inhomogeneities. Our measurements on polycrystalline and epitaxial Schottky contacts yield values in the range of 200–500nm as the typical size of inhomogeneities, covering a fraction of 0.1–1% of the total interface area.

Barrier inhomogeneities at Schottky contacts

We present a new analytical potential fluctuations model for the interpretation of current/voltage and capacitance/voltage measurements on spatially inhomogeneous Schottky contacts. A new evaluation schema of current and capacitance barriers permits a quantitative analysis of spatially distributed Schottky barriers. In addition, our analysis shows also that the ideality coefficient n of abrupt Schottky contacts reflects the deformation of the barrier distribution under applied bias; a general temperature dependence for the ideality n is predicted. Our model offers a solution for the so-called T0 problem. Not only our own measurements on PtSi/Si diodes, but also previously published ideality data for Schottky diodes on Si, GaAs, and InP agree with our theory.

Transport Properties of Inhomogeneous Schottky Contacts

We review an analytical model for the interpretation of transport measurements on spatially inhomogeneous Schottky contacts. The comparison of barriers from current/voltage- as well as from capacitance/voltage-curves permits a quantitative analysis of spatially distributed Schottky barriers. We reveal that the ideality coefficient n of abrupt Schottky contacts reflects the deformation of the barrier distribution under applied bias; a general temperature dependence for the ideality n is predicted and observed. An extension of our model includes the so-called flat band barrier of current/voltage curves. Here we demonstrate the interdependence of flat band Schottky barrier, ideality n and the homogenization of the barrier distribution under the application of a bias voltage. Effective photoresponse barriers and electrical noise at inhomogeneous Schottky diodes are also discussed.