Use of Fast Infrared Emitting Diodes with Semiconductor Detectors

Abstract

The light flash of fast infrared emitting GaAs diodes operated in forward conduction at room temperature has been used to excite particle detectors made in silicon. The 9000-Å photons have a range in silicon of 10 μ and create electron-hole pairs, simulating the absorption of a charged particle. The especially designed GaAs diodes can be pulsed with nanosecond speeds. The risetime and decay time of the light flash is less than 0.5 nsec; the time jitter between the current pulse and the light flash is less than 30 psec. The amplitude spectrum of the flash intensity follows Poisson's law applied to the number of photons emitted. The resulting spread is typically of the order of 10−3. A light flash of 1 nsec equivalent to a 5-MeV particle is easily obtained. Transient and statistical characteristics of various types of detectors are quickly measured with high accuracy. The energy calibration of detectors, the adjustment of zero time in complex setups in coincidence, the stabilization of amplifier chains are possible. The coupling of a GaAs diode to a detector yields a high performance fast current integrator.