BPW34 Commercial p-i-n Diodes for High-Level 1-MeV Neutron Equivalent Fluence Monitoring

The BPW34 p-i-n diode was characterized at CERN in view of its utilization as radiation monitor at the LHC to cover the broad 1-MeV neutron equivalent fluence (Phi_eq) range expected for the LHC machine and experiments during operation. Electrical measurements for both forward and reverse bias were used to characterize the device and to understand its behavior under irradiation. When the device is powered forward, a sensitivity to fast hadrons for Phi_eq > 2 times10¹² cm^-2 has been observed. With increasing particle fluences the forward I- V characteristics of the diode shifts towards higher voltages. At Phi_eq > 3times10¹³ cm^-2, the forward characteristic starts to bend back assuming a thyristor-like behavior. An explanation for this phenomenon is given in this article. Finally, detailed radiation-response curves for the forward bias-operation and annealing studies of the diode´s forward voltage are presented for proton, neutron and gamma irradiation.