GeSi films with reduced dislocation density grown by molecular-beam epitaxy on compliant substrates based on porous silicon

Abstract

To grow high-quality heteroepitaxial layers, we propose a compliant silicon substrate consisting of a thin epitaxial silicon film on a high-density porous layer as a membrane and an expansive low-density porous layer as a mechanical damper which shields the overlying layers from the massive wafer. GeSi films over the critical thickness have been grown by molecular-beam epitaxy on these substrates. Transmission electron microscopy analysis shows that Ge0.2Si0.8 films have no dislocations owing to just elastic strain relaxation whereas plastic flow in the pseudomorphic films that are being grown on conventional Si substrates occurs with generation of dislocations in a regular manner. The experimental data on porous silicon structure are presented in some detail and are briefly discussed in connection with substrate compliance.

HVPE GaN growth on porous SiC with closed surface porosity

“…As it has been suggested earlier, the compliance of porous substrate results in the implementation of the mechanism of mismatch strain relaxation, which is different from that typical for the growth on conventional substrate [4]. The specific character of mismatch strain relaxation mechanism in GaN films grown on PSC manifested itself in the formation of (0 0 0 1) PDs.…”

“…According to the modern concept of epitaxial growth over porous Si substrates, low surface porosity is required for achieving low defect density in epitaxial layers [4,11,12]. This is normally attained through special pore sealing procedures performed prior to the growth.…”

“…Recently, both approaches of stress controlling in heteroepitaxial film/substrate system were utilized in the growth on porous substrates. The compliant substrate approach was implemented by using a substrate based on porous Si for growing high-quality Ge 0.2 Si 0.8 heteroepitaxial layers [4]. The 'nanoheteroepitaxy' approach was employed when porous GaN substrates with high surface porosity were used for improved AlGaN growth [5].…”

Control of strain status in SiGe thin film by epitaxial growth on Si with buried porous layer

“…In addition, the use of porous Si has been discussed to accommodate lattice misfit without dislocations. 10,11 However, no significant impact on strain relaxation has been reported, owing to the nature of the interconnected growth areas. 12 In this letter, we report on our attempt to utilize continuous Si thin films with buried porous layers as a substrate for the epitaxial growth of SiGe.…”

Mechanism of the reduction of dislocation density in epilayers grown on compliant substrates

“…1 Since then, substantial efforts have been made to reproduce and apply this approach to the growth of various materials with a large lattice mismatch to many conventional substrates, such as GaN grown on a SiC-on-silicon-on-insulator compliant substrate, 2 SiGe on SOI substrates, 3 InGaAs heteroepitaxy on glass-bonded GaAs compliant substrates, 4,5 SiGe grown on prous-silicon compliant substrates, 6 InGaAs on thin twistbonded substrates, 7 dislocation-free In 0.35 Ga 0.65 P films with thickness of 300 nm grown on twist-wafer-bonded films of GaAs, 8 and GaAs grown on compliant SOI substrates. 9 To date, various degrees of success have been reported and commercial SOI substrates have been available for mass production.…”