Design Requirements for Group-IV Laser Based on Fully Strained Ge_1−xSn_xEmbedded in Partially Relaxed Si_1−y−zGe_ySn_zBuffer Layers

Abstract

Theoretical calculation using the model solid theory is performed to design the stack of a group-IV laser based on a fully strained Ge1−xSnx active layer grown on a strain relaxed Si1−y−zGeySnz buffer/barrier layer. The degree of strain relaxation is taken into account for the calculation for the first time. The transition between the indirect and the direct band material for the active Ge1−xSnx layer is calculated as function of Sn content and strain. The required Sn content in the buffer layer needed to apply the required strain in the active layer in order to obtain a direct bandgap material is calculated. Besides, the band offset between the (partly) strain relaxed Si1−y−zGeySnz buffer layer and the Ge1−xSnx pseudomorphically grown on it is calculated. We conclude that an 80% relaxed buffer layer needs to contain 13.8% Si and 14% Sn in order to provide sufficiently high band offsets with respect to the active Ge1−xSnx layer which contains at least 6% Sn in order to obtain a direct bandgap.

Low temperature epitaxial growth of Ge:B and Ge0.99Sn0.01:B source/drain for Ge pMOS devices: in-situ and conformal B-doping, selectivity towards oxide and nitride with no need for any post-epi activation treatment

“…strained-Ge grown on top of SiGeSn strainrelaxed buffer (SRB) to confine carriers for improved emission characteristics). [1][2][3][4][5][6][7][8][9] Typical requirements for p-type Ge FinFETs S/D stressors are high active doping to achieve a low contact resistivity (ρ c ), conformal doping, low thermal budget fabrication schemes, thermally stable, high crystalline quality (no precipitation or amorphous inclusions), and sufficiently large lattice constant (a) i.e. > -a a _…”

Interplay between relaxation and Sn segregation during thermal annealing of GeSn strained layers

“…1 However, for Ge 1Àx Sn x to be useful in devices it would typically require substitutional Sn concentrations of at least 5%. 2 A further important feature of Ge 1Àx Sn x (hereafter referred to as GeSn) is that substitutional Sn concentrations in the region of 7%-8% can convert Ge from an indirect into a direct bandgap semiconductor, [3][4][5][6] thereby making the construction of GeSn lasers 7,8 feasible and could open the door to Group IV, Si-based optoelectronic devices. Clearly, GeSn is an interesting material which may find a variety of applications in future microelectronic devices.…”

Electrical properties of extended defects in strain relaxed GeSn

“…3,4 Secondly, the band structure of Ge 1Àx Sn x can be tuned as a function of the misfit strain and the Sn content, and a transition from the indirect-L to direct-C bandgap can occur. 5,6 The possibility of a narrow direct bandgap makes it alluring for p-type tunnel FETs (TFETs) 7 and infrared optical components like photo-detectors, 8 light emitting diodes and lasers. 2,5 However, the Sn content required to observe indirect to direct transition increases with the magnitude of compressive strain, 2,5,6 thereby impelling the use of strain-relaxed Ge 1Àx Sn x .…”

“…5,6 The possibility of a narrow direct bandgap makes it alluring for p-type tunnel FETs (TFETs) 7 and infrared optical components like photo-detectors, 8 light emitting diodes and lasers. 2,5 However, the Sn content required to observe indirect to direct transition increases with the magnitude of compressive strain, 2,5,6 thereby impelling the use of strain-relaxed Ge 1Àx Sn x . The high compressive strain due to the lattice mismatch between Ge 1Àx Sn x and Ge/ virtual-Ge or Si substrates is released above a critical epitaxial layer thickness.…”