Capacitance–voltage and admittance spectroscopy of self-assembled Ge islands in Si

We investigate the electrical properties of self-assembled Ge islands embedded in Si Schottky diode structures by means of capacitance–voltage measurements and admittance spectroscopy. The Ge islands form at T=550 °C by self-assembly in the Stranski–Krastanow growth mode with an area density of 4.5×109 cm−2. Their diameter and height are 70 and 6.5 nm, respectively. A linear increase of the thermal activation energy observed in voltage-dependent admittance spectroscopy shows that the ensemble of Ge islands has a low, continuous, averaged density of states.