Research On Ge Photodetector For CMOS And Silicon Photonic Integration

With the development of the society,people hope the processing,computing,transmission,storage of information become faster and faster,but energy consumption become as low as possible.And then higher requirements of the integrated circuits which play a import role in information put forward.Silicon-based photo-electronic technology can make full use of existing mature CMOS process.Combining with high transmission and the strong anti-interference of the photon to overcome the bottlenecks in micro-electronic technology.So it has become a research hotpot allover the world in recent years.As Ge has a large absorption coefficient and high carrier mobility at 1.3?m to 1.55?m near infrared communication band and the manufacturing of Ge film can be compatible with the mature CMOS process.These making Ge widely used in silicon-based photonics integration.It has become a trend to manufacture a waveguide integrated photodetector with silicon-based heteroepitaxial growth Ge film.Therefore,it is important to manufacture high quality silicon-based Ge film at first for a high-response,low dark current and highbandwidth photodetector.In this paper,we investigated the growth of the epitaxial Ge film on patterned Si/SiO2 substrate with 40 nm low temperature Ge buffer layer by reduced pressure chemical vapor deposition(RPCVD)adjusting GeH4 and HCl etching gas flow.Then,annealing 20 minutes in the H2 atmosphere to reduce the dislocation and defect in the epitaxial Ge.Testing results show that the dislocation pits density of epitaxial Ge in 10 microns diameter circular area of patterned substrate is as low as 1.3×106/cm2,the full-width-at-half maximum of diffraction peak of epitaxial Ge with a thickness of 1.5?m of the XRD profile is about 240 arcsec.The surficial roughness of epitaxial Ge is as low as 0.2nm measured by AFM after chemical mechanical polishing(CMP)process.The Ge film material is expected to integrate applicated in silicon-based detector and other silicon-based optoelectronic devices.In this paper,the SOI-based waveguide integrated lateral germanium photo-detector which is fully compatible with CMOS process is fabricated with the epitaxial germanium method.This photodetector without doped Ge or Ge-metal contacts,no additional damage defects introduced in the germanium film.The device shows a dark current of 16.6nA at-1V bias and a responsivity of 0.593A/W,a quantum efficiency of ?=47.8% at-1V bias,at 1.56?m wavelength.A 3dB bandwidth of 15 GHz at-3V bias has been measured.We also demonstrate open eye diagram at 30 Gbps.