HERA-B detectors with p-spray isolation on the n-side; unirradiated results

p-spray isolation of double-sided detectors is investigated by computer simulations and measurements on full-size detector prototypes. Simulations showed that a B p-spray implant doses 4·10¹² , 6·10¹², and 8·10¹² cm^-2 and implant energy 60 keV would yield breakdown voltages above 200 V for unirradiated detectors with oxide charge 2·10¹¹ cm^-2. The simulations showed that the breakdown voltage decreases with increasing p-spray dose. According to the computer simulations, the detectors should perform equally well after irradiation giving an oxide charge of 1·10¹² cm^-2 . HERA-B strip detectors with p-spray isolation were manufactured, using the three simulated doses. The average breakdown voltages and standard deviations were 167±31 V for the 4·10¹² cm^-2 dose, 151±16 V for the 6·10¹² cm^-2 dose, and 127±13 V for the 8·10¹² cm^-2 dose. The measured decrease in breakdown voltage is in good agreement with the computer simulations