Reverse graded relaxed buffers for high Ge content SiGe virtual substrates

Abstract

An innovative approach is proposed for epitaxial growth of high Ge content, relaxed Si1−xGex buffer layers on a Si(001) substrate. The advantages of the technique are demonstrated by growing such structures via chemical vapor deposition and their characterization. Relaxed Ge is first grown on the substrate followed by the reverse grading approach to reach a final buffer composition of 0.78. The optimized buffer structure is only 2.8μm thick and demonstrates a low surface threading dislocation density of 4×106cm−2, with a surface roughness of 2.6nm. The buffers demonstrate a relaxation of up to 107%.

Electrical isolation of dislocations in Ge layers on Si(001) substrates through CMOS-compatible suspended structures

“…Since the Ge is epitaxially grown on Si it has no adhesion issues, which sometimes can occur in metal mask layers [20], and can also be doped during epitaxy, thus avoiding additional implantation steps. In addition, Ge has been reported with spintronic [21], optical detection [22] and lasing [23] abilities and is an accommodating buffer for further SiGe layers [24,25] and III-V materials on Si [26]. Epitaxial Ge on Si(001) is, however, plagued by electrical leakage due to conduction through the dislocation network still present in the layer [27][28][29][30].…”

Optical absorption in highly strained Ge/SiGe quantum wells: The role of Γ→Δ scattering

“…18,19 The bottom layer of the device was p-doped with boron at 1 × 10 19 cm −3 , on which was grown a 100-nm-thick intrinsic SiGe spacer, the MQW layers, a second 100-nm-thick intrinsic spacer layer, an ntype SiGe layer doped with phosphorous at 1×10 19 cm −3 , and finally a 2-nm-thick Si cap layer. 80-µm-diameter circular mesas were etched to form vertical p-i-n diodes, and a Ti/Al metal stack was deposited and sintered at 400 • C for 30 minutes to form electrical contacts.…”

An origin behind Rashba spin splitting within inverted doped sGe heterostructures

“…Finally, a small peak f4 = 38 Hz is observed which corresponds to 13 ff  and is believed to be from Zeeman spin splitting 5,11 . Spin splitting of the HH level has been shown to occur because of cubic Rashba SOI 7 , while for the LH linear Rashba SOI.…”