Site‐controlled SiGe islands on patterned Si(001): Morphology, composition profiles, and devices

Abstract

Deterministic control of position on a substrate, uniform size and shape are prerequisite for most of the envisioned applications of SiGe islands in electronic and optoelectronic devices. As an example of electronic application, tensile strained Si layers on top of coherent SiGe islands may be used as channels for field effect transistors (FETs) with enhanced electron mobility. For such a kind of application, site-controlled islands are required to allow for their external addressability. In this feature article we investigate the morphological and compositional evolution of site-controlled SiGe islands on pit-patterned Si(001) substrates. We then report on the first demonstrated n-channel FET with enhanced electron mobility based on SiGe islands. Finally, a new approach for further increase of the tensile strain is presented.

Interpolating function of the strain relief of epitaxial quantum dots via an alternative morphological descriptor

“…The surface energy contribution can play an important role in some subtle cases where a precise quantitative balance of the terms is needed [19,[25][26][27]. But most commonly the sequence of the evolution observed experimentally agrees well * daniele.scopece@empa.ch; daniele.scopece.science@gmail.com with the one predicted by considering the elastic energy term alone (governing the evolution from flatter to steeper islands), both on flat [15,20] and on patterned substrates [8].…”

“…III B. In experiments the distribution of intermixed islands observed is typically nonhomogeneous [8,44,59,60], but it has been proven that the three-dimensional concentration profile obtained is the one minimizing the elastic energy [23,61,62].…”

“…The bottom-up solution to create nanosized objects currently represents a widely explored technique to overcome the limitations of top-down nanolithography for materials with novel and tunable properties for new technological nodes. High-gain photosensors [1,2], devices with quantum optical properties [3], efficient thermoelectrics [4][5][6], high-speed transistors [7,8], and the efficient strain engineering of the recently introduced membranes [9,10] represent just a few examples of the applications that are feasible. The properties of the final devices depend critically on the morphology of the nanostructures and on their evolution and/or stability during processing [11].…”

Effect of strain on the electronic and optical properties of Ge–Si dome shaped nanocrystals

“…Furthermore, Ge-Si nanostructures with various shapes (domes, wire, lens, and pyramids) have been fabricated and integrated in optical and electrical devices using advanced fabrication techniques such as molecular beam epitaxy (MBE), 19 self-assembly, [20][21][22] and chemical vapor deposition (CVD). 8 These devices exhibit size dependent characteristics and show potential for future devices such as thin-film field effect transistors, 7 flash memory, 8,10 DotFETs, 23 photodetectors, 24 solar cells, 25,26 and quantum computers. 15,16,27,28 Inter-level optical transitions in Ge-Si NCs have attracted interest due to the TYPE-II band alignment at the Ge and Si interface causing the holes and electrons to be spatially separated in the Ge and Si regions, respectively.…”