Jurgen Michel

Totally relaxed GexSi1-x layers with low threading dislocation densities grown on Si substrates

We have grown compositionally graded GexSi1−x layers on Si at 900 °C with both molecular beam epitaxy and rapid thermal chemical vapor deposition techniques. Triple‐crystal x‐ray diffraction reveals that for 0.10<x<0.53, the layers are totally relaxed. GexSi1−x cap layers grown on these graded layers are threading‐dislocation‐free when examined with conventional plan‐view and cross‐sectional transmission electron microscopy. Electron beam induced current images were used to count the low threading dislocation densities, which were 4×105±5×104 cm−2 and 3×106±2×106 cm−2 Eq. 2×106 cm−2 for x=0.23 and x=0.50, respectively. Photoluminescence spectra from the cap layers are identical to photoluminescence from bulk GexSi1−x.

Impurity enhancement of the 1.54‐μm Er3+ luminescence in silicon

The effect of impurity coimplantation in MeV erbium‐implanted silicon is studied. A significant increase in the intensity of the 1.54‐μm Er3+ emission was observed for different coimplants. This study shows that the Er3+ emission is observed if erbium can form an impurity complex in silicon. The influence of these impurities on the Er3+ photoluminescence spectrum is demonstrated. Furthermore we show the first room‐temperature photoluminescence spectrum of erbium in crystalline silicon.

Microstructure of erbium-implanted Si

A study is presented of the relation between microstructure and 1.54 μm photoluminescence (PL) in high‐energy ion‐implantated Er in Si as a function of implant dose, energy, and temperature and subsequent anneal. Transmission electron microscopy (TEM) of material implanted at 500 keV and ≳100 °C and annealed at 900 °C to activate the Er PL suggests the solubility of Er in Si to be ≊1.3±0.4× 1018 cm−3 at 900 °C. Precipitates take the form of platelets (probably ErSi2) ≊100–300 A in diameter and ≊10 A thick. The 1.54 μm PL saturates at ≊5× 1017 cm−3, before the apparent solubility limit. Layers in which the Si is fully amorphized and subsequently regrown by solid phase epitaxy during an anneal show increased Er incorporation in the crystalline Si but segregation at the amorphous‐crystalline interface. In buried amorphous layers regrown from top and bottom, segregation leads to a line of high Er concentration near the center of the layer: Regrowth from a single interface leads to a segregation pileup of Er a...

The electrical and defect properties of erbium‐implanted silicon

A detailed study of the electrical and defect properties of ion‐implanted erbium in silicon shows that erbium doping introduces donor states. The concentration of erbium related donors as a function of implant dose saturates at 4×1016 cm−3 at a peak implanted Er‐ion concentration of (4–7)×1017 cm−3. The defect levels related to erbium in silicon are characterized by deep level transient spectroscopy and identified as E(0.09), E(0.06), E(0.14), E(0.18), E(0.27), E(0.31), E(0.32), and E(0.48). The dependence of the photoluminescence on annealing temperature for float zone and for Czochralski‐grown silicon show that oxygen and lattice defects can enhance the luminescence at 1.54 μm from the erbium. Temperature‐dependent capacitance‐voltage profiling shows donor emission steps when the Fermi level crosses EC − ET = 0.06 eV and EC − ET = 0.16 eV.

Elimination of dislocations in heteroepitaxial MBE and RTCVD Ge x Si 1-x grown on patterned Si substrates

We have grown GexSi1-x (0 <x < 0.20,1000–3000Å thick) on small growth areas etched in the Si substrate. Layers were grown using both molecular beam epitaxy (MBE) at 550° C and rapid thermal chemical vapor deposition (RTCVD) at 900° C. Electron beam induced current images (EBIC) (as well as defect etches and transmission electron microscopy) show that 2800Å-thick, MBE Ge0.19Si0.81 on 70-μm-wide mesas have zerothreading and nearly zero misfit dislocations. The Ge0.19Si{0.81} grown on unpatterned, large areas is heavily dislocated. It is also evident from the images that heterogeneous nucleation of misfit dislocations is dominant in this composition range. 1000Å-thick, RTCVD Ge0.14Si0.86 films deposited on 70 μm-wide mesas are also nearly dislocation-free as shown by EBIC, whereas unpatterned areas are more heavily dislocated. Thus, despite the high growth temperatures, only heterogeneous nucleation of misfit dislocations occurs and patterning is still effective. Photoluminescence spectra from arrays of GeSi on Si mesas show that even when the interface dislocation density on the mesas is high, growth on small areas results in a lower dislocation density than growth on large areas.

Carbon reactions in reactive ion etched silicon

Reactive ion etching (RIE) of silicon creates interstitial defects in the near surface region which diffuse into the bulk material and are trapped at substitutional carbon sites. Photoluminescence (PL), current-voltage (I–V), and Rutherford backscattering (RBS) measurements show that silicon etched in a CF4 + 8%O2 or SF6 + 8%O2 plasma consists of two distinct regions, adisplacement damage region extending 1000Å from the surface and apoint defect reaction region which can extend to depths > 1 μm. The size of the point defect reaction region is determined by diffusion limited trapping of the interstitial silicon generated during the RIE resulting in the formation ofCi - Oi orCs-Ci defect pairs. The long range diffusion rate of the interstitial defects is enhanced by the plasma during the RIE processing, and by a recombination enhanced reaction path.

Photoluminescence investigations of graded, totally relaxed Ge x Si 1- x structures

MBE grown, totally relaxed, graded GexSi1-x on Si heterostructures were studied by using photoluminescence spectroscopy at 4.2 K. The existence and linewidth of the near band gap bound exciton recombination confirms the high quality of these layers. Due to the relaxation we find dislocation related D-bands in the near infrared region of the photoluminescence spectra. The dislocation band D4 proved to be an effective tool for measuring residual strain in the heteroepitaxial layer because of its large line-shift in the presence of strain. We found tensile strain of 0.4% at the interface between the SiGe layer and the Si substrate.

Athermal Silicon Ring Resonators

We demonstrate athermal amorphous Si (a-Si) ring resonators using a top polymer cladding. We observe near complete thermo-optic (TO) compensation, and a temperature dependent resonant wavelength shift (TDWS) as low as 0.5 pm/K is achieved.

Light up the Future of Silicon Microprocessors

United States. Defense Advanced Research Projects Agency. Electronic and Photonic Integrated Circuit (EPIC) Program

Large Diameter, CMOS-Manufacturable Photodetectors for over 2 Gbps Polymer Optical Fiber Applications

Lateral p-i-n photodetectors were fabricated in a CMOS-compatible process. The 200µm diameter devices had a bandwidth of 1.7 GHz, suitable for 2.5 Gbps operation. An unexpected illumination intensity dependance was observed and confirmed by simulation.