Investigation On The Performance Of Short-wave Infrared GeSn Photodevices Modulated By Semiconductor Energy Band

Group Ⅳ Ge enables the ultimate realization of silicon-based light sources and is expected to be an ideal material for promoting silicon-based optoelectronic integration and optical interconnect in short-wave infrared because of the small energy difference between L valley withΓvalley and plasticity of bandgap.However,the L valley of Ge is located below theΓvalley and the low internal quantum efficiency restrict the light absorption and luminous efficiency of silicon-based Ge photonic devices.The addition of negative bandgap semiconductorα-Sn can transform Ge Sn alloy into direct bandgap material,but the low solid solubility of Sn in Ge（<1%）and 14%lattice mismatch leading to the segregation of Sn,which limit the modulation action to the bandgap of Ge Sn alloy.In order to solve this problem,strain engineering combined with Sn components which used to modulate the band structure of Ge Sn alloy and enhance the performance of Ge Sn optoelectronic devices are theoretically studied.The crystal structures of Ge and Ge Sn alloys are optimized based on the first principles of density functional theory.The crystal structures and band structures of Ge_1-xSn_x alloys with different Sn components are theoretically studied,the indirect-to-direct transition of Ge Sn alloys will be realized when Sn content reaches 6.63%.The indirect-to-direct transition of Ge will be realized with 2.97%uniaxial tensile strains along[001]direction,corresponding to the bottom energy of conduction band is 0.27 e V,which is much less than relaxed Ge.In this paper,a strain-adjustable Ge_0.92Sn_0.08 light-emitting diode with the giant magnetostrictive stressor is designed and investigated theoretically for the influence of strain engineering on the basis of bandgap modulation.A 0～0.11%non-contact adjustable uniaxial tensile strain is introduced into Ge_0.92Sn_0.08 with the giant magnetostrictive material Tb_0.3Dy_0.7Fe_1.95 used as adjustable stressor by adjusting the external magnetic field.A continuously adjustable bandgap from 0.543 e V to 0.475 e V of the Ge_0.92Sn_0.08 alloy is achieved and the spontaneous emission rate of the strained LED is enhanced about 3.63 times compared with the relaxed device.Meanwhile,an adjustable range of luminous peak is achieved from2.18μm to 2.46μm,and the boundary of luminous wavelength was extended to 2.61μm.Besides,the structure of a type-II double heterojunction photodetector with adjustable stressor Tb_0.3Dy_0.7Fe_1.95 is designed and simulated according to the modulation of bandgap in Ge Sn,Si Ge Sn alloys and the mechanism of interlayer strain introduction.A continuously adjustable bandgap from 0.534 e V to 0.461 e V of the Ge_0.90Sn_0.10 alloy corresponding to the continuously adjustable detection wavelength of 2.45μm～2.76μm of shortwave infrared is achieved,which provides a new idea for the integration of next-generation optical communication systems in shortwave infrared.