Current- and capacitance-voltage characteristics of Cd/p-GaTe Schottky barrier diodes under hydrostatic pressure

Abstract

Schottky barrier diodes (SBDs) on p-type GaTe have been fabricated by Cd metallization and characterized by current–voltage (I–V) and capacitance–voltage (C–V) techniques as a function of hydrostatic pressure (0.0–7.0 kbar). The evaluation of the experimental data reveals a decrease of barrier height (Φb), ideality factor (n) and series resistance (Rs) with an increase in the hydrostatic pressure. The zero-bias barrier height, ideality factor and series resistance values for the Cd/p-GaTe SBD by I–V measurements have been in the range of 0.743–0.682 eV, 1.246–1.219 and 30.5–16.4 Ω for the 0.0–7.0 kbar pressure interval, respectively. C–V measurements at 1.0 MHz have resulted in higher barrier heights than those obtained from I–V measurements. The discrepancy between Schottky barrier heights (SBHs) obtained from I–V and C–V measurements is explained by the introduction of a spatial distribution of SBHs due to barrier height inhomogeneities that prevail in the metal/GaTe interface. The change of barrier height values (Φb(0) − Φb(P)) obtained from the I–V and C–V techniques turns out to have a mean linear pressure coefficient of −8.77 ± 0.10 meV kbar−1 (=−87.7 ± 1.0 eV GPa−1), approximately equal to that found for the band gap of GaTe. We have concluded that the variation of the barrier height due to the applied pressure should follow precisely the variation of the semiconductor band gap, accepting that the Fermi level is a reference level which is pinned to the conduction-band minimum (CBM) as a function of the pressure.