Analog Frontend Circuits for Avalanche Photodiodes

摘要

The aims of this work is to design low noise electronics for optical sensing and X‐rayudspectroscopy using Sheffield‐grown Avalanche photodiodes(APD).udA transimpedance amplifier(TIA) for a 2.0 μm LIDAR system is designed and tested as partudof a project funded by ESA. Numerical analysis is provided for the TIA in addition to SPICE andudexperimental analysis. Characterisation of the TIA shows that a noise equivalent power of lessudthan 100 fW/√Hz can be achieved with an optimised InAs APD. Preliminary results of a TIA‐InAsudmodule at 2.0 μm is presented.udA low noise charge sensitive preamplifier(CSP) with a novel local feedback is designed andudcharacterised. The CSP shows a better noise performance than commercially available CSP suchudas the CoolFet 250. The CSP is also characterised for APD dark current of up 4 μA and the CSP isudfound to behave well for such relatively high dark current. Discrepancies between the SPICEudmodel and measured characteristic of the CSP’s input JFET is presented and discussed.udThe first ever Aluminium Indium Phosphide (AlInP) APD X‐ray spectroscopy measurementudis presented in this work. AlInP is the widest band material that can be grown latticematchedudon a GaAs substrate. Due to its wide bandgap, AlInP can offer reverse dark current ofudless than 2 pA at gain of 100 for a 200um device, making it desirable for room temperatureudoperation. An energy resolution of 647 eV is obtained for AlInP APD coupled to the CSP andudexposed to 55Fe X‐rays.udUsing the CSP presented in this work, previously reported GaAs/AlGaAs APD isudcharacterised and compared with results obtained using a commercial CSP. A 21% improvementudin X‐ray energy resolution is reported, despite degradation in the APD.