Enhanced photoluminescence of multilayer Ge quantum dots on Si(001) substrates by increased overgrowth temperature

Abstract

Four-bilayer Ge quantum dots (QDs) with Si spacers were grown on Si(001) substrates by ultrahigh vacuum chemical vapor deposition. In three samples, all Ge QDs were grown at 520 °C, while Si spacers were grown at various temperatures (520 °C, 550 °C, and 580 °C). Enhancement and redshift of room temperature photoluminescence (PL) were observed from the samples in which Si spacers were grown at a higher temperature. The enhancement of PL is explained by higher effective electrons capturing in the larger size Ge QDs. Quantum confinement of the Ge QDs is responsible for the redshift of PL spectra. The Ge QDs’ size and content were investigated by atomic force microscopy and Raman scattering measurements.

Morphology and structure evolution of multilayered Ge/Si quantum dots grown by magnetron sputtering

“…Besides, the Raman character peaks of Ge-Ge and Ge-Si in three sampes shown a gradually enhanced red shift compared with their intrinsic peak positions of the bulk materials (300.5 and 402 cm − 1 respectively). This phenomenon was consistent with the results observed by Liu and cheng et al [22], and it usually attributed to the synergistic effect of the stress relaxation, QDs size and atomic intermixing changed by the rising temperature [13].…”

“…As the development of research, multilayer QDs t the requirement of photonic device in a structure and improve device performance effectively [5,6]. In the past decade, the researchers mainly focused on single-layer growth technics of QDs, multi-layer QDs prepared methods also had been explored by the conventional low-rate deposition technics, such as molecular beam epitaxy (MBE) [7,8], chemical vapor deposition (CVD) [9] and modi ed chemical vapor deposition (MCVD) [10]. In the growth technics mentioned, high requirements for temperature control (MBE), the reaction products may become surface impurities (CVD), especially the high cost of equipment and maintenance, and low deposition rate, have become major obstacles to the industrialization of highquality QDs.…”

“…In the past decade, much research mainly focused on single-layer growth technics of QDs, multi-layer QDs prepared methods also had been explored by the conventional low-rate deposition technics, such as molecular beam epitaxy (MBE) [7,8] and chemical vapour deposition (CVD) [9,10]. Some recent typical work on multi-layer Ge/Si QDs involves that Chu et al [11] reported the work of using low growth temperature (Ge below 400 • C, Si below 500 • C) to inhibit the formation of Ge nano islands in multi-layer Ge/Si films grown by low-pressure CVD to fabricate and demonstrate stacked Ge nanosheets GAA FET CMOS inverter, Storozhevykh et al [7] studied the influence of the critical thickness and stress distribution of the intermediate layers formed in the Ge/Si heterostructure on atomic mixing and structure of multi-layer Ge/Si QDs grown by MBE, Smagina et al [12] manufactured multi-layer Ge/Si QDs with ordered spatial arrangement and novel photoluminescence properties by adjusting the parameters (diameter and spatial period) of pits on the SOI substrate and depositing Si isolation layers with appropriate thickness (25 nm) based on MBE technology.…”

Structural and electrical investigations of MBE-grown SiGe nanoislands

“…4b. It is also noticeable that the slight local Si-Si vibrations shoulder observed at 455 cm −1 in both samples may have emerged since the layers are grown extremely thicker compared to a few atomic layers [33,34,37]. However, due to rich top Ge content in SiGe-3 and SiGe-4, Si-Si vibration peaks are not observed at all since it is possible that Raman signal from lower layers were surpassed by the 100 nm top Ge layer.…”

“…This result suggests that some portion of the samples could possess amorphous contents. In comparison with the size found by the XRD and Raman data analyses, the size found by the XRD can be considered to be more reliable due to fact that X-rays have relatively higher penetration depth with respect to the laser light used in the Raman measurement [33,34]. Furthermore, the size found using the phonon confinement model (PCM) [35,36] includes estimation only for Ge-Ge located at ca.…”