Characterization of Predictable Quantum Efficient Detector

The aim of this thesis is to develop new characterization methods for Predictable Quantum Efficient Detector (PQED) at visible wavelengths and to extend the predictable responsivity range of PQED into short visible and ultraviolet (UV) spectral ranges. The thesis presents optical studies of PQEDs made of p- and n-type photo diodes, including determination of responsivity, reflectance, spatial uniformity, and bias-voltage dependent characteristic in expanded spectral range compared to previous studies. Investigations of internal quantum efficiency of silicon detectors were done at UV spectral range. A theoretical model for quantum gain in silicon photodiodes was developed for short visible and UV spectral ranges. The n-type PQED with Al2O3 layer coating was optically characterized at short and long visible wavelengths. Its responsivity was obtained through comparison measurements against reference p-type PQED. Reflectance losses were measured and compared with simulated values and found to agree. With these measurements n-type PQED responsivity is predictable in visible range. Novel p-type PQEDs with SiNx surface layer were characterized against reference p-type PQED. It was found out that SiNx PQEDs have excellent spatial uniformity and at least as high responsivity as the used reference PQED. Responsivity of PQED and Hamamatsu trap detector was studied in UV range by comparison measurements against room temperature pyroelectric radiometer. With predicted reflectance and recombination losses, absolute value of quantum gain was retrieved from measured responsivity of PQED. Based on measured data of quantum yield, a theoretical model for quantum yield was developed for short visible and UV wavelengths. Calculated quantum gain has very good agreement with measured values at short visible wavelengths. Separation of contributions of quantum gain and reflectance in responsivity allowed to estimate recombination losses of Hamamatsu photodiodes that was not reported before. A new way of analysing PQED photocurrent dependence on bias voltage was also proposed. Such data can be used for fitting of a 3D charge-carrier transport model which was utilized in a separate work to predict fundamental parameters of PQED photodiodes and to determine spectral responsivity with an unprecedented accuracy.