Fabrication of a high-performance Ge/Si PIN photodetector utilizing Ge/Si hetero-bonding with a microcrystalline Ge interlayer.

We present a high-performance Ge/Si PIN photodetector that leverages the advanced Ge/Si hetero-bonding method. The sputtered microcrystalline Ge is utilized as the interlayer, in conjunction with Smart-Cut technology, to fabricate high-quality Si-based Ge films. The exfoliated Ge film exhibits a surface roughness of 0.196 nm and a full width at half maximum of XRD peak of merely 70 arcseconds, which is much lower than that of the epitaxial ones. The Ge/Si PIN photodetectors based on the exfoliated Ge films are systematically optimized and analyzed, with particular emphasis on the effects of crystal quality and interlayer thickness on device performance. The device with a 2 nm-thick Ge interlayer demonstrates a dark current density of 32.8 mA/cm at a bias of -1 V, accompanied by an ideality factor as low as 1.33. At a wavelength of 1310 nm, the device achieves a responsivity of 0.61 A/W, and Ge devices featuring a 13 µm-diameter mesa exhibited a high 3 dB bandwidth of 24.3 GHz. The interlayer hetero-bonding technology effectively facilitates the integration of photodetectors onto Si platforms, offering substantial potential for a diverse array of applications.