Self-assembled Quantum Wells Research Articles

Light emission from erbium-doped nanostructures embedded in silicon microcavities

We present the findings of high-efficient Er 3+-related 4 I 13/2↔ 4 I 15/2 absorption and emission from self-assembled quantum wells (SQW) embedded in silicon microcavities. The microcavities are prepared by the short-time diffusion of boron into the Si (1 0 0) wafer doped with erbium. The intraband electron transitions accompanied by tunneling through strongly coupled SQW series are observed to excite the 4 I 13/2↔ 4 I 15/2 Er 3+ -intracenter emission, 1.54 μm , that is enhanced by strong sp–f mixing in the range of the Rabi splitting revealed by the transmission spectra.

Observation of large optical anisotropy and valence band splitting in AlInAs self-assembled lateral quantum wells

Self-assembled lateral quantum wells in alloys of AlInAs, epitaxially deposited by metal–organic chemical vapor deposition on InP, are studied by transmission electron microscopy, modulation spectroscopy, and photoluminescence. Under particular growth conditions, the growth of a homogeneous layer results in the spontaneous self-assembly of a sequence of quantum wells with quantization axes oriented along the [110] direction. With respect to a homogeneous alloy of similar average composition, the band gap reduction observed is as large as 360 meV. A polarization anisotropy exceeding 90% is observed for the lowest energy transition and a large valence band splitting of 139 meV separates the heavy- and light-hole-like valence bands.

Single impurity centers embedded in self-assembled silicon microcavities

We present the findings of high efficient light absorption in self-assembled quantum wells (SQW) embedded in silicon microcavities that exhibit a distributed feedback identified by the FIR transmission spectra. The photo and electroluminescence from SQW is found to be enhanced in the range of the Rabi splitting. The intraband hole transitions are shown to give rise to a fast energy transfer into the d-shell transitions of the center incorporated into the microcavity which is caused by the strong sp-d mixing in the built-in electric field and revealed by the intracenter emission.

Light emission from erbium doped nanostructures embedded in silicon microcavities

We present the findings of high efficient Er 3+-related 4I 13/2↔ 4I 15/2 absorption and emission from self-assembled quantum wells (SQW) embedded in silicon microcavities. The microcavities of this art are prepared by the short-time diffusion of boron into the Si(1 0 0) wafer doped with erbium. The intraband electron transitions accompanied by tunneling through strongly coupled SQW series are observed to excite the 4I 13/2→ 4I 15/2 Er 3+-intracentre emission that is enhanced in the range of the Rabi splitting revealed by the transmission spectra.

Self-Assembled Impurity Superlattices and Microcavities in Silicon

We present ultra-shallow (5-30 nm) diffusion profiles performed by short-time boron diffusion from the gas phase into the n-type Si(100) wafer using controlled surface injection of selfinterstitials and vacancies. The diffusion profiles of this art are found to consist of both self-assembled longitudinal and lateral quantum wells formed naturally between the δ barriers heavily doped with boron. The deformed potential fluctuations created by self-interstitials microdefects embedded into the p-diffusion profile are shown to cause the formation of self-assembled microcavities that are revealed by the light transmission spectra.

The K.U. Leuven pulsed-field facility solid-state physics in high magnetic fields

The pulsed-field facility has five parallel measuring stations. Most functions of each experiment, in particular, the control of the capacitor bank, data recording and cryogenics, are controlled by a central computer which is part of a network for data processing and is linked by fiber optics to the capacitor bank and the stations. User magnets are designed to work reliably up to 50–60 T with a pulse duration of the order of 20 ms. The pulse can be extended by a crowbar circuit. The available cryogenic equipment includes flow cryostats, 4He bath cryostats, 3He bath cryostat and a 50 mK dilution refrigerator. Physical properties such as magnetization, magneto-transport phenomena, far-infrared (FIR) optical absorption and photoluminescence (PL) in the visible and near infrared can be studied. The solid-state research is focused on the following topics: the normal state transport properties of high-temperature superconductors, the study of magnetic systems as spin-Peierls compounds, Mn-Oxide GMR materials and Fe-Oxide garnet compounds, and low-dimensional semiconductors such as self-assembled quantum dots and quantum wells.

Low Temperature Impurity Diffusion into Large-Band-Gap Semiconductors

Low temperature diffusion of boron and phosphorus has been performed for the first time into the monocrystalline diamond and 6H-SiC wafers through the controlled surface injection of vacancies. By varying the parameters of the surface oxide and polycrystalline silicon overlayer during the boron/phosphorus diffusion process, it was possible to obtain the planar quantum-size pn and np junctions respectively in the 6H-SiC and diamond wafers as well as the 6H-SiC transistor structures. The first findings of the high temperature (77 K) quantized conductance and single-hole transistor operation are present, which identify the formation of self-assembled quantum wells inside ultra-shallow pand ndiffusion profiles. These large-band-gap nanostructures are shown to cause the high electroluminescence efficiency of the diamond and 6H-SiC p-n junctions.