Strain engineering of Ge by ion irradiation and alloying

Germanium (Ge) is a traditional but promising material in integrated circuit (IC) due to the high mobility of hole carrier and highly compatibility in Si base-IC technology. However, the indirect band structure of Ge leading to low radiative recombination efficiency, limiting the application in opto-electronics. Strain engineering is a promising method to obtain energy band modification in semiconductors. Noble ions (He, Ar) are expected to induce tensile strain via bubbles formation or vacancy-related defect formation in Ge. A bubble-rich structure formation is accompanied by strongly amorphization process during 30 keV Ar+ ions irradiation, while fully liquid-phase epitaxy is necessary to achieve a high-quality crystalline structure. 4 MeV He+ ions irradiation in Ge can obtain a defect related tensile strain in Ge, which can be evaluated via Raman peak shift. IV-group heavy ions (Sn, Pb) alloying can lead a strong energy bandgap modification in Ge while the GeSn-alloy laser grown by RPCVD can work at low temperature. Here we use CMOS-compatible ion implantation to achieve a tensile GeSn alloy which shows a larger peak shift toward low wavenumber in Raman measurement. The photoconductivity detector based on Ge0.97Sn0.03 alloy shows a photo response to 1550 nm laser source.