Dislocations in Germanium: Mechanical Properties

doi:10.1007/978-3-540-85614-6_1

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“…It is noteworthy that the pits observed here have precisely the same shapes (i.e. square for the (001) and triangular for the (111) substrate) as those produced by preferential chemical etching of dislocations on Ge(001) and Ge(111) [42,43]. Therefore, we expect that, also in the present case, dislocations play a critical role in the formation of pits.…”

Section: Annealing-induced Pit-like Defects On Ge(001) and Ge(111)supporting

confidence: 68%

“…Notably, the temperature needed for the formation of pits was comparable to that used for ultra-high-vacuum (UHV) surface cleaning of Ge [40,41] and for the graphene/Ge growth [30][31][32]. The pits were morphologically very similar to those produced by preferential chemically etching of dislocations [42,43]. The density of the defects depends on the maximum temperature reached, the number of thermal cycles performed and, above all, on the wafer orientation.…”

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confidence: 93%

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Formation of extended thermal etch pits on annealed Ge wafers

Persichetti

Fanfoni

Seta

et al. 2018

Applied Surface Science

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An extended formation of faceted pit-like defects on Ge(001) and Ge(111) wafers was obtained by thermal cycles to T> 750 °C. This temperature range is relevant in many surface-preparation recipes of the Ge surface. The density of the defects depends on the temperature reached, the number of annealing cycles performed and correlates to the surface-energy stability of the specific crystal orientation. We propose that the pits were formed by preferential desorption from the strained regions around dislocation pile-ups. Indeed, the morphology of the pits was the same as that observed for preferential chemical etching of dislocations while the spatial distribution of the pits was clearly non-Poissonian in line with mutual interactions between the core dislocations. * luca.persichetti@uniroma3.it I. INTRODUCTIONDespite recent advances in the van der Waals epitaxy of two-dimensional semiconductors [1-7], bulk group-IV still plays a leading role in current complementary-metal-oxide-semiconductor (CMOS) technology. Within group IV, non-siliconoriented research is mainly devoted to Ge. SiGe heterostructures monolithically grown on Si are the ideal test bed for understanding alloying [8][9][10][11] and the interplay between elastic/plastic relaxation at the nanoscale [12-22] Their also being promising candidates for integrating optical communications into a CMOS platform, thanks to their optical properties potentially compatible with the C-band transmission window [23]. Ge wafers, on the other hand, are the substrates of choice for the epitaxial growth of high-efficiency multi-junction solar cells based on III-V semiconductors [24][25][26][27][28][29] and have also been shown to be suitable CMOS compatible templates for graphene overgrowth [30][31][32]. All these applications require a highlydemanding surface quality of the epi-ready Ge substrates. Indeed, any deviation from a perfect surface will be a nucleation point for a defect or a cause of a non-uniform epi-stack. In particular, one of the main issues affecting the manufacturing of semiconductor wafers is the formation of extended secondary defects such as crystal-originated pits (COPs) and L-pits (also referred to as A-Swirls) resulting from the aggregation of intrinsic point defects [33]. While COPs are voids produced by the aggregation of vacancies, it is generally assumed that the formation of L-pits is related to dislocation loops either intrinsically formed during the wafer manufacturing [34,35] or by misfit strain in the case of SiGe heteroepitaxy [36]. In the former case,

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Section: Annealing-induced Pit-like Defects On Ge(001) and Ge(111)supporting

confidence: 68%