Charge carrier traffic at self-assembled Ge quantum dots on Si

• Published in: Solid-state electronics Vol. 83; pp. 99 - 106
• Main Authors: Kaniewska, M., Engström, O., Karmous, A., Oehme, M., Petersson, G., Kasper, E.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Kidlington Elsevier Ltd 01-05-2013; Elsevier
• Subjects: Applied sciences; Capacitance; Cross-disciplinary physics: materials science; rheology; Deep level transient spectroscopy; Depletion; Diodes; Electric potential; Electronic transport in quantum dots; Electronics; Exact sciences and technology; Materials science; Methods of deposition of films and coatings; film growth and epitaxy; Microelectronic fabrication (materials and surfaces technology); Molecular beam epitaxy; Molecular, atomic, ion, and chemical beam epitaxy; Nanoscale materials and structures: fabrication and characterization; Physics; Quantum confined energy states; Quantum dots; Self-assembled Ge/Si quantum dots; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Silicon; Surface morphology; Self-assembled Ge/Si quantum dots; Molecular beam epitaxy; Quantum confined energy states; Electronic transport in quantum dots; Deep level transient spectroscopy; Surface morphology; Self assembly; Deep level transient spectrometry; Quantum dot; Diode; Charge carrier; Tunnel effect; Surface structure; Microelectronic fabrication; p type semiconductor; Silicon; Activation energy; Low temperature; Voltage capacity curve; Potential energy; Potential distribution; Energy distribution; Doped materials; Mean value; Valence band; Thermal activation; Germanium
• ISSN: 0038-1101; 1879-2405
• DOI: 10.1016/j.sse.2013.01.025

► Germanium quantum dots grown by MBE are characterized using two capacitance-based methods. ► The results provide information on the energy distribution of quantum dot states. ► Lower-temperature grown quantum dots had a wider distribution of energy states. ► The thermal activation energy for hole emission was found to be close to 0.40eV.
Germanium quantum dots (QDs) have been characterized by deep level transient spectroscopy (DLTS) and capacitance versus voltage (C–V) technique. Two types of dots, grown by molecular beam epitaxy (MBE) at different temperatures, were investigated and assessed with respect to morphological properties. Samples with dots grown at 350°C, were designed as n++–p–p++ silicon junctions with the QDs positioned in the depleted p-region, while a second type of samples were Shottky diodes based on medium doped silicon with the QDs prepared at 550°C and positioned in the Schottky depletion region. From the combined results of temperature scanned and frequency scanned DLTS, and by varying hole filling levels of the QD potentials, the energy distribution of states in the QD potentials were investigated. A wider distribution was found for the low-temperature QDs, probably related with a larger variation of size. By using a technique for separating tunneling and thermal hole emission, the average thermal activation energy for emitting holes to the valence band was found close to 0.40eV for both types of QDs.