Due to their interesting size-dependent properties, semiconductor Quantum Dots (QDs) have many potential applications in nanoelectronics and optoelectronics. Ge QDs are particularly attractive because of the compatibility of Ge with Si technology and the ability to grow dislocation-free Ge QDs through the Stranski-Krastanov growth mode. Recently given examples include mm-wave circuit operation [1] with Ge QD Schottky diodes of 1.1 THz transit frequency or room temperature single electron memory [2] function of double (Si,Ge) dots. In this paper the voltage dependent occupation of states and their filling dynamics is investigated in two terminal device structures (Schottky barrier diode, p/n junction) by capacitance voltage (C-V) and deep level transient spectroscopy (DLTS) methods. Frequency scanned DLTS (FS-DLTS) was used, where the DLTS signal at a constant temperature is measured as a function of the repetition frequency of electrical pulses, f, with the emission voltage of the pulses, VR, as a parameter. Presenting DLTS spectra as a contour plot on a (f, VR)-plane, where contour lines with negative (positive) slope reflect signals related to thermal (tunnelling) transitions makes it possible to distinguish between these emission paths.
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