## 4 Conclusions  
In this paper, the recent progress in the epitaxial growth technique using the InP-based membrane on a Si substrate and its contribution for integrating of low-operation energy membrane photonic devices on a Si substrate have been reviewed. Use of the thin III-V membrane structure makes it possible to carry out high-quality epitaxial growth on an InP-on-insulator substrate. The thickness-dependence of the high-temperature tolerance of a III-V-on-insulator substrate was revealed both theoretically and experimentally. In  
Figure 16: (**a**) Bird’s eye view of an laser diode (LD)-Mach-Zehnder modulators (MZM) integrated chip; (**b**,**c**) cross-sectional SEM images of distributed feedback (DFB) LD and phase shifter; (**d**) lasing spectrum of output light from MZM output port; (**e**) eye diagram with 28 Gbit/s NRZ signal.  
addition, the growth of quaternary compound semiconductors such as InGaAs MQWs and InGaAsP bulk on an InP-on-insulator substrate was demonstrated. The TDD in InGaAs MQWs evaluated with a PL microscope was less than 4.0 \(\times\) 10\({}^{2}\)/cm\({}^{2}\), which is even lower than the typical commercially available InP wafer specification. TEM measurement also revealed that there is no obvious structural degradation in MQWs grown on an InP-on-insulator substrate. Using this growth technique, a 1.3-\(\upmu\)m-range directly modulated laser array on a Si substrate was fabricated. The fabricated laser array exhibited 25.8-Gbit/s direct modulation at 50 \({}^{\circ}\)C with bias currents from only 8.0 to 8.3 mA and lasted up to 95 \({}^{\circ}\)C. In addition, a multi-wavelength DML array with optimized-bandgap MQWs was demonstrated using the selective-area growth of multi-wavelength MQWs on an InP-on-insulator substrate. Selective-area growth enables full-O-band bandgap control of InGaAs MQWs over 150 nm. Furthermore, integration of a DFB laser and InGaAsP MZM was demonstrated using selective regrowth of InGaAsP bulk material on the InP membrane on Si-photonics circuits.  
To manufacture PICs using epitaxial regrowth techniques, demonstrating scalability will be the next important step. There is essentially no difficulty up to 150-mm wafer because both the InP wafer and MOVPE system are already available. To integrate InP on 200- and 300-mm Si wafer, die-to-wafer bonding technologies can resolve the wafer-size mismatch between Si and InP [76]. In addition, Smart Cut and epitaxial lift-off are promising technologies to fabricate InP-on-insulator substrate at low cost because these technologies enable reuse of the donor InP wafer [77; 78]. We believe that the epitaxial growth techniques using an InP-on-insulator substrate are scalable and paving the way for providing a promising approach for establishing III-V/Si PICs for future data-center networks.  
Conceptualization, S.M.; methodology, T.F., T.H., T.S. and S.M.; software, K.T. and T.K.; validation, T.F., T.H., T.A., H.N., K.T., T.S. and T.T.; formal analysis, T.K.; investigation, T.F., T.H., T.A., H.N., K.T., T.S. and T.T.; writing--original draft preparation, T.F.; writing--review and editing, S.M.; visualization, T.F.; supervision, S.M.; project administration, S.M. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Not applicable.  
The data that support the findings of this study are available from the corresponding author upon reasonable request.  
The authors thank [PERSON], [PERSON], [PERSON], [PERSON], and [PERSON] for their great help with device fabrication. The authors also thank [PERSON] for his valuable suggestions and fruitful discussions.  
The authors declare no conflict of interest.