Epitaxial InGaAsP/InP photodiode for registration of InP scintillation

Operation of semiconductor scintillators requires optically tight integration of the photoreceiver system on the surface of the scintillator slab. We have implemented an efficient and fast quaternary InGaAsP pin photodiode, epitaxially grown on the surface of an InP scintillator wafer and sensitive to InP luminescence. The diode is characterized by an extremely low room-temperature dark current, about 1 nA/cm² at the reverse bias of 2 V. The low leakage makes possible a sensitive readout circuitry even though the diode has a large area (1×1 mm²) and therefore large capacitance (50 pF). Results of electrical, optical and radiation testing of the diodes are presented. Detection of individual α-particles and γ-photons is demonstrated.