Study On Low Noise Near-infrared InGaAs Focal Plane Detectors

Lattice-matched InGaAs/InP focal plane detectors are widely used in military equipment,space remote sensing,medical diagnostics,and safety monitoring.Combined the development requirements of high-performance near infrared focal plane detectors,this paper studied the physical mechanism and preparation process of low-noise,large-scale InGaAs focal plane detectors.The noise model of the near infrared InGaAs focal plane was established.For the detectors,the main influencing factors of the focal plane noise are capacitance and dark current.Next,the capacitive characteristics and dark current characteristics of the detectors were analyzed.The optoelectronic performance of the detector was simulated using sentaurus TCAD.The dark current characteristics of devices with different concentrations were analyzed for the unit device,and the dark current model of the focal plane was established.The diffusion processing of the planar InGaAs detector was optimized.The PL spectroscopy was used to characterize the diffusion damage of planar InGaAs detectors.The quantum efficiency of planar InGaAs detectors was studied.Detecotors with low-capacitance and low-dark current were prepared.The preparation process of high-density small-pitch area array was optimized,and the high-density and small-pitch test structure was prepared according to the optimized process.The 15?m pitch 1280×1024 InGaAs focal plane arrays were prepared,and the focal plane performance was tested and analyzed.The 10?m pitch 2560×2048 InGaAs focal plane arrays were prepared by using optimized process.The noise characteristics of near infrared InGaAs focal plane were analyzed,improved the focal plane noise model.According to the analysis of the focal plane noise model,two kinds of 25?m pitch 160×120 focal plane arrays with different dark current and capacitance properties were prepared.The noise characteristics at different temperature and integral time were tested.It is found that the noise during the short integral time can be suppressed by reducing the dopant concentration of the absorber.When the temperature is reduced,the noise of the detector with low absorber doped concentration is still small.It is proved that the detector capacitance can be reduced by lowering the concentration of absorber layer,thus depressing the coupling noise.The capacitance characteristics of the InGaAs detector were mearsured and fitted.The fitting doping concentrations of the three kinds of devices were 1.53×10¹⁵ cm^-3,5.14×10¹⁵ cm^-3 and 2.40×10¹⁶ cm^-3,respectively,closed to the given concentration,1×10¹⁵ cm^-3,5×10¹⁵ cm^-3 and 5×10¹⁶ cm^-3.Two devices with different extended electrode were fabricated.The theoretical difference between the two was 145 fF,and the test result was 130 fF.The photoelectric properties of the diffusion junctions in the InP cap layer and the InGaAs absorber layer were simulated using the Sentaurus TCAD software.When the junction was in the InP cap layer,the dark current was 0.47 fA,but the quantum efficiency was almost neglected,when located in the InGaAs absorber layer,the dark current is 22 fA.In order to achieve quantum efficiency comparable to the InGaAs junction,it is necessary to increase the reverse bias voltage to-0.9 V,resulting in an increase in dark current to 42 fA.The relationship between dark current and doping concentration,minority carrier lifetime and size structure of cell devices and array detectors were simulated respectively.The dark current model of high-density array detectors was established.The diffusion process of low doping concentration materials was optimized,and finally the detector with low dark current and low capacitance was obtained.The dark current density was 5.9 nA/cm² and the capacitance density was 7.9 nF/cm².The D^*was 1.3×10¹² cmHz^1/2/W,the quantum efficiency was 96%.The preparation process of high-density and small-pitch area arrays was improved,and the high-density and small-pitch area array test structure was prepared by optimized process.The design and process of large array with 15?m pitch and 10?m pitch were obtained.The 15?m pitch 1280×1024 InGaAs near infrared focal plane arrays were prepared,the D^*was 2.76×10¹² cmHz^1/2/W,the quantum efficiency was 70%.The 10?m pitch 2560×2048 InGaAs focal plane arrays were prepared by using optimized process and structural parameters.