Intersubband Transition Engineering in the Conduction Band of Asymmetric Coupled Ge/SiGe Quantum Wells

Abstract

n-type Ge/SiGe asymmetric-coupled quantum wells represent the building block of a variety of nanoscale quantum devices, including recently proposed designs for a silicon-based THz quantum cascade laser. In this paper, we combine structural and spectroscopic experiments on 20module superstructures, each featuring two Ge wells coupled through a Ge-rich tunnel barrier, as a function of the geometry parameters of the design and the P dopant concentration. Through the comparison of THz spectroscopic data with numerical calculations of intersubband optical absorption resonances, we demonstrated that it is possible to tune by design the energy and the spatial overlap of quantum confined subbands in the conduction band of the heterostructures. The high structural/interface quality of the samples and the control achieved on subband hybridization are the promising starting point towards a working electrically pumped light-emitting device.

Electron-phonon coupling in n -type Ge two-dimensional systems

“…Our samples consist of a stack of 20 strain-compensated QWs deposited on a reverse step-graded virtual substrate as detailed in Ref. [7]. Six samples feature a symmetric QW geometry with a Ge well with varying thickness w, and a 21 nm thick Si0.20Ge0.80 barrier (see Table I).…”

“…Structural investigation of the grown samples, performed by high-resolution X-ray diffraction and scanning transmission electron microscopy, revealed high crystal quality, very sharp and flat interfaces and a very good layer thickness and composition reproducibility along the entire stack 7 .…”

“…Due to a more mature epitaxy technology, carrier scattering in low dimensional systems has been investigated mainly focusing on III-V based structures 2,3 . However, in the last two decades, advances in group-IV epitaxy have made possible to grow SiGe multilayer systems with high crystal quality [4][5][6][7][8] ; consequently this class of materials is attracting increasing research efforts, mainly motivated by its prompt integrability with the mainstream CMOS standard. In particular, in the last ten years, SiGe Ge-rich structures have been actively investigated, and applications have been proposed in different contexts as for instance quantum computing [8][9][10] , Si-based photonics [11][12][13] , high mobility transistors 14,15 , and thermoelectricity 16,17 .…”

Smart Materials for Dynamic Thermal Radiation Regulation

“…The study provided insights into the enhancement of the selectivity and sensitivity of spectroscopy applications even in extremely hot conditions. Besides the structures above which concentrate on MIR, in other literature, [ 105–107 ] quantum well‐based multilayer structures were designed to modulate emissivity in the THz region which can be applied in electrically modulated incandescent sources and cascade laser devices. This provides novel ideas for emissivity modulation in MIR.…”

In-Situ Annealing and Hydrogen Irradiation of Defect-Enhanced Germanium Quantum Dot Light Sources on Silicon

“…Practical, Si-compatible, monolithically-integrated lasers are the main missing ingredient towards the realization of efficient and low-cost integrated silicon photonics circuits that are designated to uplift fields of on-chip data communication [1][2][3] and on-chip sensing [4]. There has been substantial recent progress in the field ranging from the integration of III-V quantum dot (QD)-lasers on Si [5][6][7] to all-group-IV approaches [8][9][10][11][12]. Independently of the fabrication method used, the stability of the light emission with respect to the typical thermal budget of a CMOS process is of key importance.…”