D. Grützmacher

Analysis of the Metallic Phase of Two-Dimensional Holes in SiGe in Terms of Temperature Dependent Screening

We find that temperature dependent screening can quantitatively explain the metallic behavior of the resistivity on the metallic side of the so-called metal-insulator transition in p-SiGe. Interference and interaction effects exhibit the usual insulating behavior which is expected to overpower the metallic background at sufficiently low temperatures. We find empirically that the concept of a Fermi liquid describes our system with its large interaction parameter r(s) approximately 8.

Single-hole transistor in a p-Si/SiGe quantum well

A single-hole transistor is patterned in a p-Si/SiGe quantum well by applying voltages to nanostructured top gate electrodes. Gating is achieved by oxidizing the etched semiconductor surface and the mesa walls before evaporation of the top gates. Pronounced Coulomb blockade effects are observed at small coupling of the transistor island to source and drain.

Strategies to Improve Optical Gain and Waveguide Loss in Strain-Compensated SiGe Quantum Cascade Mid-Infrared Emitters

Strain-compensated p-type SiGe quantum cascade (QC) structures are promising candidates to realize an efficient Si-based light source. In this paper, we present the strategies to improve the optical gain and to minimize the waveguide loss to develop a SiGe QC laser for mid-infrared wavelength

Coexistence of weak localization and a metallic phase in Si/SiGe quantum wells

Magnetoresistivity measurements on p-type Si/SiGe quantum wells reveal the coexistence of a metallic behavior and weak localization. Deep in the metallic regime, pronounced weak localization reduces the metallic behavior around zero magnetic field without destroying it. In the insulating phase, a positive magnetoresistivity emerges close to B=0, possibly related to spin-orbit interactions.

Influence of capping on strain, composition and shape of SiGe islands

The rearrangement of SiGe islands during the deposition of Si was studied by a combination of scanning tunneling microscopy, transmission electron microscopy and high-resolution X-ray diffraction. With increasing silicon capping of the islands, an increasing flattening accompanied by a rising intermixing could be determined. Using a finite element calculation, which served as an input for X-ray simulations, the strain distribution within the islands was obtained.

Analysis of the resistance of two-dimensional holes in SiGe over a wide temperature range

The temperature dependence of a system exhibiting a ‘metal–insulator transition in two dimensions at zero magnetic 2eld’ (MIT) is studied up to 90 K. Using a classical scattering model we are able to simulate the non-monotonic temperature dependence of the resistivity in the metallic high density regime. We show that the temperature dependence arises from a complex interplay of metallic andinsulating contributions containedin the calculation of the scattering rate 1 =� D(E; T ), each dominating in a limited temperature range. ? 2002 Elsevier Science B.V. All rights reserved.

Intersubband quantum cascades in the Si/SiGe material system

AbstractSi=SiGe quantum cascade structure of 3 × 4 periods show well-resolved intersubband electroluminescence, whose non-radiativelifetimesarefoundtodependstronglyonthedesignofthequantumwellstructure,andareshowntoreachvaluescomparabletothatofanequivalentGaInAs=AlInAslaserstructure.ProblemsthatneedtobeovercomefortherealizationofaSi=SiGequantumcascadelaserarediscussedinrelationtostructuresonrelaxedSiGebuerlayers.InitialexperimentsusingSi 0:2 Ge 0:8 =SionSi 0:5 Ge 0:5 buerlayersshowwell-resolvedintersubbandabsorptionbetweentwoheavyholestatesinthequantumwells.? 2002ElsevierScienceB.V.Allrightsreserved. Keywords:Intersubband; Quantumcascade;SiGe 1. IntroductionThequantumcascade(QC)laserisrapidlyadvan-cing as a viable option for mid-IR emission, cover-ing today a large wavelength range, 3–24 m. Withan improved understanding of the intersubband pro-cesses, it has been possible to extend the operationtocontinuousmodeandroomtemperatureoperation[1]. The conception of a laser working through in-tersubbandtransitionshasalsospurredaninterestforapplyingthesameideastoSi-basedheterostructures,whoseindirectbandgapisalargeimpedimenttoe-cientinterbandlightemissionandlasing.Incontrast,forintersubbandemissionthenatureofthebandgapisinconsequential.ThemotivationforaSi-QClaseristwofold.WithSiMOSFETtechnologydominating

Strain compensated Si/SiGe quantum well and quantum cascade on Si0.5Ge0.5 pseudosubstrate

This study follows up our previous investigation of the valence band (VB) intersubband emission from quantum cascade structures grown lattice matched on Si substrates. Here, Si/Si1−xGex(x=80%) heterostructures are investigated which are deposited by MBE on a virtual substrate of relaxed SiGe containing 50% of Ge. TEM analysis reveal flat and abrupt interfaces for structures grown at temperatures Tgrowth≈300°C. Intersubband absorption and photoluminescence emission manifest well-defined interfaces and good material quality. The observed intersubband line positions are found to be in good agreement with k·p model calculations for the VB. This is in contrast to the observed type II no phonons recombination which is found at consistently lower energy than expected. Finally, electrically excited intersubband emission from a strain compensated cascade structure containing three periods is presented.

Si/SiGe quantum cascade structures emitting in the 10 μm range

Abstract In this paper, we report on the successful deposition of Si/SiGe quantum cascade (QC) structures by molecular beam epitaxy (MBE). The structures are pseudomorphically grown on Si in the metastable regime, thus low temperature (T=350xa0°C) deposition is required. Structural characterization has been performed using transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray reflectivity (XRR). The data indicate an interface roughness of about 2 monolayers and an excellent correlation of the layer periodicity within the stacks of cascades. Electroluminescence (EL) has been observed for several different p-type Si/SiGe QC structures. The observed energy agrees with the energy calculated for the HH2 to HH1 intersubband transition in the active well of the cascade structure and shows the expected confinement shift in dependence of the Ge concentration and the well width. The EL is strongly p-polarized. The results clearly indicate that the observed EL originates from the desired intersubband transition. The EL persists up to temperatures exceeding 180 K. The non-radiative lifetime of the HH2 state reaches values of about 0.5 ps, which is comparable to those of III/V QC structures.

Strategies to improve optical gain and waveguide loss in SiGe quantum cascade devices

Strain-compensated p-type SiGe quantum cascade structures are promising candidates to realize an efficient Si-based light source. Here we report strategies to improve the optical gain and waveguide loss to develop a SiGe quantum cascade laser.