Optical properties of individual site-controlled Ge quantum dots

Abstract

We report photoluminescence (PL) experiments on individual SiGe quantum dots (QDs) that were epitaxially grown in a site-controlled fashion on pre-patterned Si(001) substrates. We demonstrate that the PL line-widths of single QDs decrease with excitation power to about 16 meV, a value that is much narrower than any of the previously reported PL signals in the SiGe/Si heterosystem. At low temperatures, the PL-intensity becomes limited by a 25 meV high potential-barrier between the QDs and the surrounding Ge wetting layer (WL). This barrier impedes QD filling from the WL which collects and traps most of the optically excited holes in this type-II heterosystem.

Enhanced Telecom Emission from Single Group-IV Quantum Dots by Precise CMOS-Compatible Positioning in Photonic Crystal Cavities

“…For the high-quality ( Q )-factor modes (M0, M1 with Q > 10 000) and the low- Q -mode group (M2–M4, Q < 3000) two optimal PCR sets were identified with a = 357 nm and a = 378 nm, respectively, and r / a = 0.31 (simulation results for the PCR modes M0–M4 given in Section I of the Supporting Information ). Note that due to the prepatterned growth approach, our Ge QDs are very homogeneous with respect to composition profile and size 38 and exhibit a broad time-averaged emission spectrum typical for the material system 39 and the employed pumping intensity. Therefore, the emission spectra of the QDs on our PCR chip are comparable under the given experimental conditions, and the time-averaged spectral width of each dot is large enough to include all cavity modes of the selected high- or low- Q group.…”

“…To enhance spectral overlap between the cavity modes and QD emission, a rather high laser excitation power of 750 μW was chosen, which has been shown to cause significant spectral broadening of the time-averaged emission spectrum of single Ge QDs. 39 …”

Assessing Carrier Recombination Processes in Type‐II SiGe/Si(001) Quantum Dots

“…This is much broader than the lifetime‐limited emission linewidth, which is to be expected in the µeV range, considering reported radiative lifetimes for SiGe . Different interpretations of the broad PL linewidth of SiGe QDs include: i) size inhomogeneity of the QDs, ii) compositional inhomogeneity between different QDs in an ensemble, iii) state filling effects, iv) bi‐exciton formation at higher excitation intensities, v) existence of a low‐energy phonon replica, vi) photo‐induced band‐bending effects, vii) spectral diffusion and fast dephasing …”

“…The typical photoluminescence emission (PL) of randomly nucleated Ge/Si QDs is spectrally very broad and can to some extent be narrowed by using site‐controlled QDs on patterned substrates . The PL emission from a single SiGe QD grown on a pit‐patterned substrate with wide pit period shows an inhomogeneous linewidth of about 16 meV even for the lowest measurable excitation powers. This is much broader than the lifetime‐limited emission linewidth, which is to be expected in the µeV range, considering reported radiative lifetimes for SiGe .…”

Исследование структурных и излучательных свойств Ge(Si) квантовых точек, упорядоченных на поверхности Si(001)

“…Упорядочение квантовых точек (КТ) в свою очередь является ключевым фактором для их практического применения в микро-и наноэлектронных устройствах, которые включают в себя запоминающие устройства, лазеры и транзисторы [5,6]. Так, например, рост GeSi-структур на структурированных подложках позволил получить отдельные наноостровки, встроенные в фотонно-кристаллические микрорезонаторы [6][7][8], что привело к значительному увеличению интенсивности сигнала фотолюминесценции (ФЛ) и сужению линий ФЛ в спектрах отдельных КТ. Существуют различные способы создания структурированной поверхности по-лупроводниковых подложек [9][10][11][12].…”