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This work demonstrates a high-performance photodetector with a 4-cycle Ge 0.86 Si 0.14 /Ge multi-quantum well (MQW) structure grown by reduced pressure chemical vapor deposition techniques on a Ge-buffered Si (100) substrate. At -1 V bias, the dark current density of the fabricated PIN mesa devices is as low as 3 mA/cm 2 , and the optical responsivities are 0.51 and 0.17 A/W at 1310 and 1550 nm, respectively, corresponding to the cutoff wavelength of 1620 nm. At the same time, the device has good high-power performance and continuous repeatable light response. On the other hand, the temperature coefficient of resistance (TCR) of the device is as high as -5.18%/K, surpassing all commercial thermal detectors. These results indicate that the CMOS-compatible and low-cost Ge 0.86 Si 0.14 /Ge multilayer structure is promising for short-wave infrared and uncooled infrared imaging.

Monolayer (ML) Ga 2 O 3 with outstanding properties is promising for advanced nanodevice applications; however, its high exfoliation energy makes obtaining it challenging. In this study, we propose a more efficient solution to obtain ML Ga 2 O 3 by exfoliation from indium-doped bulk β-Ga 2 O 3 . The exfoliation efficiency with the assistance of In-doping and the doping influence on the stability and structural and electronic properties of ML Ga 2 O 3 are systematically studied using first-principles calculations. The exfoliation energy of ML Ga 2 O 3 is found to be reduced by 28% and is of the same order of magnitude as that of typical van der Waals (vdWs) 2D materials. Besides, excellent stability is preserved for ML Ga 2 O 3 at extremely high In doping concentration by phonon spectrum and ab initio molecular dynamics inspections. The bandgap of ML Ga 2 O 3 decreases from 4.88 to 4.25 eV with increased In concentration, and the modification of the VBM converts ML Ga 2 O 3 to a direct bandgap semiconductor. With the suppression of ZA mode phonon scattering, the pristine and In-doped ML Ga 2 O 3 exhibit high electron mobility, whereas the strong electron-phonon coupling (EPC) effect significantly decreases the hole mobility. Finally, the transfer characteristics of 5 nm MOSFETs based on the pristine and In-doped ML Ga 2 O 3 with varied In concentrations are simulated based on the non-equilibrium Green's function (NEGF) formalism. The I on for HP has a maximum of 3060 μA μm -1 at In doping concentration of 5% and is triple that of the pristine ML Ga 2 O 3 for LP at In doping concentration of 20%. The FOMs of n-type MOSFETs based on the In-doped ML Ga 2 O 3 and typical 2D materials are compared and shows huge potential for sub-5 nm applications. Our study applies a new strategy for obtaining ML Ga 2 O 3 and can also improve the device performance at the same time.

Here, SiGeSn nanostructures were grown via molecular beam epitaxy on a Si (111) substrate with the assistance of Sn droplets. Owing to the thermal effect and the compressive strain induced by a lattice mismatch, Si and Sn atoms were successfully incorporated into the Ge matrix during the Sn-guided Ge deposition process. A low growth temperature of 350 °C produced a variety of SiGeSn nanostructures of different sizes, attributed to the variation of the initial Sn droplet size. Using energy-dispersive X-ray spectroscopy, the Sn, Si and Ge contents of a defect-free SiGeSn nanoisland were approximately determined to be 0.05, 0.09 and 0.86, respectively. Furthermore, as the growth temperature increased past 600 °C, the growth direction of the nanostructure was changed thermally from out-of-plane to in-plane. Meanwhile, the stacked SiGeSn nanowires grown along the 〈112〉 direction remained defect-free, though some threading dislocations were observed in the smooth SiGeSn nanowires along the 〈110〉 direction. These results offer a novel method to grow Si-based SiGeSn nanostructures while possessing important implications for fabricating further optoelectronic devices., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)