Investigation On Optical And Electrical Performances Of Silicon Vacancy Centers In Diamond

Color centers in diamond have drawn increasing attention in the fields of Quantum Information Processing,Integrated Nanophotonics and Bioluminescence Imaging for their extraordinary optical performances,namely,high monochromaticity and stability,spin readability and room temperature(RT)operability.Compared to those extensively investigated nitrogen-vacancy(NV)centers and neutrally-charged silicon-vacancy(SiV0)centers,negatively-charged silicon-vacancy(SiV-)centers have been proved to be an ideal optical structure and stable RT single photon source with their shorter excited-state lifetimes(1～4 ns),narrower phonon-sideband width(≈5 nm),and higher monochromaticity(over 70%photoluminescence(PL)concentrated).In this paper,various optoelectronic devices based on Si-doped epitaxial diamond films were fabricated through Microwave Plasma Chemical Vapor Deposition(MPCVD)with Tetramethylsilane(TMS)injected.The microstructures of the materials and devices as well as the optical and electronic performances of SiV centers were investigated.Firstly,different diamond/n-Si vertical heterostructures were fabricated by depositing[001]-orientated high-quality silicon-doped microcrystalline-diamond(MCD)films on n-Si substrates with different doping concentrations.Subsequently,the charge-state regulation of SiV centers was carried out using high-temperature air annealing and electric field,respectively.Although air annealing can produce oxygenterminated diamond surface,it is difficult to regulate the charge states of color centers in MCD due to the size effect.For the method of electrical tailoring,the H-Dia/n+-Si device composed of hydrogen-terminated diamond and heavily doped n-Si exhibited a rectification ratio of 102 and a PL increasement by 2-fold of SiV-at 50 V forward bias.Band structure analysis shows that the electron tunneling process from the n-Si to the diamond leads to abundant transformations from SiV0 to SiV-,which provides a feasible approach for charge state regulation of SiV centers,particularly,to increase the number of high-performance negatively-charged(SiV-)centers.Secondly,Si-doped single-crystal diamond(Si-SCD)epitaxial layers with different surface states were deposited on a high-quality single-crystal diamond(SCD)substrate,then the in-plane diamond photodetectors with interdigital electrodes were prepared by photolithography.It is found that the oxygen-terminated device obtained by multi-step oxidation is suitable for high-performance devices with an ideal dark current of several picoamperes,which is much lower than that of the hydrogenterminated device.In addition,even though the introduction of SiV centers into the devices enhances the Near Ultraviolet/Visible absorptions,it has little effect on the detection performance for solar blind signals.The on-off ratio of both SCD and Si-SCD under 220 nm irradiation can reach 104,and the responsivities equal 46.8 mA/W and 36.2 mA/W,respectively.However,Si-SCD exhibits 102～103 times higher Near Ultraviolet/Visible responsivities and longer response time than SCD,owing to the photoionization process of SiV centers and Schottky-Read-Hall(SRH)recombination of photogenerated carriers at the SiV defect levels.Moreover,when applying electric fields to the interfinger electrodes of Si-SCD,a 1.4-fold PL increasement of SiV-can also be achieved at 60 V bias,and the calculated enhancement efficiency is much higher than the MCD heterojunction devices.