Radiation detection using integrated GaAs HEMT electronics

A charge sensitive preamplifier (CSP) together with a shaper was integrated using the standard 0.3 μm GaAs HEMT process of the “Fraunhofer-Institut für Angewandte Festkörperphysik” (IAF) on a 100 × 1000 μm2 large chip area. The shaper has a filter time constant τf = 10 ns to minimize the noise of the CSP, which was measured to be 450 rms electrons at an input capacitance CT = 1.55 pF. The circuit is operated with negative supply voltages of −3.5 and −4.5 V giving a total power dissipation of 20 mW. The overall amplification into 50 Ω is 18.8 mV/fC, corresponding to a 75 mV output signal for a charge of 25 000 electrons, which is the signal generated by 1 minimum ionizing particle (MIP) in a 200 μm thick GaAs or 300 μm thick Si detector. To demonstrate the functionality of a fully GaAs based detection system the chip was wire-bonded to a GaAs pad detector and used at the T10 testbeam facility of the PS accelerator at CERN to record spectra of 5 GeV pions.