A new approach to the determination of MS-barrier heights from photoelectric data and/or an alternative way to determine the value of the Richardson constant

Abstract

The short circuit current ( I sc ) and the open-circuit voltage (V oc) of MS-diodes were measured making use of internal photoemission. The Schottky barrier heights were then obtained by the usual extrapolation of Fowler plots [1] corrected according to the operational method presented before [2]. Combining the equation for the short circuit current and open circuit voltage of an illuminated junction (from the equivalent circuit) with the equation relating saturation current to barrier height we then sum up alternative methods of using I sc , V oc data: (a) Fowler plots using either I sc or V oc to deduce φ B ; (b) using I sc and V oc (for any wavelength or average over a certain range) to deduce the barrier height φ B , if the effective Richardson constant A ∗∗ (and the tunneling transmission coefficient θ) are assumed known; (c) using I sc and V oc to deduce A ∗∗ (and then m ∗ or θ (in the product θA ∗∗ if the φ B values derived from Fowler plots or/and common IV-data (thermal current) are assumed correct. This approach could lead to the determination of several parameters ( A ∗∗ , m ∗ , etc.) as a function of temperature, crystal orientation or for different semiconductors. The interrelation of the methods is shown in flow diagram form. Measurements on Rh- nSi diodes are taken as an example, and the agreement between φ B values from the different methods is shown to be excellent, if a lower than usual A ∗∗ value is used (which follows the published trend of A ∗∗ with field strength). The Fowler method is based upon knowledge of the response per incident photon as a function of the wavelength. The importance of monitoring the light actually incident upon the metal interface is pointed out.