INFLUENCE OF TEMPERATURE ON THE I-V AND C-V CHARACTERISTICS OF SI DETECTORS IRRADIATED AT HIGH FLUENCES

Measurements of I-V and C-V characteristics of non-irradiated and irra diated silicon detectors, at fluences 1.2 x 10(13) n/cm(2) less than o r equal to Phi less than or equal to 5.9 x 10(14) n/cm(2), were made i n forward and reverse bias at low temperatures. An abrupt increase of the value of forward current was found at given bias voltages V-S. Thi s value increases with increasing values of Phi. The capacitance was m easured at reverse bias V-R, at omega = 10 kHz, and at temperatures 10 K less than or equal to T less than or equal to 200 K. The capacitanc e is a function of applied reverse bias, but for a given critical temp erature T-c, it does not change any more and remains constant for all applied values of V-R. This value of T-c depends on Phi. For increasin g Phi, the critical temperature T-c increases, e.g. for a non-irradiat ed sample, T-c = 20 K and for a sample irradiated at Phi = 5.9 x 10(14 ) n/cm(2), T-c = 150 K. The observed phenomena can be explained assumi ng a freeze-out of free carriers at very low T, and space-charge-limit ed current (SCLC) for the very low concentration of majority carriers.