The Study Of Single Photon Detection Based On InGaAs/InAlAs Avalanche Photodiodes And Their Applications

Single-photon avalanche photodiodes（SPADs）can detect single photon,therefore,they have been widely used in fields requiring highly sensitive light detection,such as free space optical（FSO）communications,photon counting communications systems,laser radar systems,etc.In Ga As/In P SPADs are commonly used and commercially available in the near-infrared region.Compared with the In Ga As/In P SPADs,InGaAs/InAlAs SPADs have the advantages of lower temperature coefficient of breakdown voltage and higher potential detection efficiency,so it is expected that InGaAs/InAlAs SPADs have greater potential to be operated in the fields without the cryogenic equipment.However,the studies on InGaAs/InAlAs SPADs are insufficient,the mesa structure is mostly adopted in the previously reported InGaAs/InAlAs SPADs and the quenching circuits type is relatively simple.In order to achieve highly sensitive light detection and complete the studies of InGaAs/InAlAs SPADs,this thesis studies the performances of home-made planar InGaAs/InAlAs SPADs under uncooled conditions with sine wave gate（SWG）quenching circuits,and the performances of InGaAs/InAlAs SPADs applied in photon counting communication system are experimentally studied.In addition,dynamic biasing technology is used to reduce excess noise,which effectively improves the signal-to-noise ratio（SNR）.The main works are as follows:（1）The home-made planar InGaAs/InAlAs SPADs are theoretically and experimentally studied under uncooled conditions.（1）The impacts of the thickness of the absorption layer and multiplication layer on NEP are theoretically studied.NEP can comprehensively characterize the performances of SPADs since it is calculated in consideration of PDE and DCR.（2）The planar structure is adopted in the device fabrication for avoiding damage to the side wall of the InGaAs/InAlAs SPADs,which can reduce the dark current and increase gain.（3）The performances of InGaAs/InAlAs SPADs are experimentally studied,and the 100 MHz SWG quenching circuit is adopted to quench the SPADs.When excess voltage is 2.1 V,the PDE,DCR,P_af,and time jitter are10.4%,3.1 MHz,1.2%,and 170 ps respectively.NEP of 3.07×10^-15 W/Hz^1/2 is achieved,which is the lowest value among reported InGaAs/InAlAs SPADs operated under room temperature.（2）The performances of an InGaAs/InAlAs SPAD applied in photon counting communication system are theoretically and experimentally studied.（1）The impacts of different factors on bit error rates（BER）are theoretically studied,and these factors include the number of gates in bit time（n）,the extinction ratio（ER）,P_d,and P_af.（2）The SWG frequency is increased to 1.8 GHz to achieve high data rate transmission,and the time jitter for the system is reduced to 53 ps with a PDE of 8%.The NRZ-OOK code is adopted in the experiment to study the BER characteristics.The sensitivities of-57.2 d Bm(BER=1.4×10^-3),-53.42 d Bm(BER=2×10^-3),-51.06 d Bm(BER=3.5×10^-3)are achieved at 100 Mbit/s,200 Mbit/s and 400 Mbit/s respectively.（3）The excess noise of dynamic biasing APDs is experimentally studied.The concept of a“transition zone”is proposed,which is between the linear mode and Geiger mode.Combined with the dynamic biasing technology,it is demonstrated experimentally that the excess noise decreases with gain when the APDs are operated in the transition zone.The maximum useful gain is as high as 620 in the dynamic biasing mode,which shows a greater promotion than that of the DC biasing mode（17.5）.Compared with the traditional DC biasing mode,the optimal SNR for dynamic biasing mode is improved by 14 d B without the degradation of response time as the peak optical power is 525 nW.