Beam test measurements on GaAs strip and pixel detectors

• Published in: Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment Accelerators, spectrometers, detectors and associated equipment, 1998-06, Vol.410 (1), p.1-5
• Main Authors: Albertz, D, Braunschweig, W, Breibach, J, Gräßel, D, Kubicki, Th, Lübelsmeyer, K, Rente, C, Röper, Ch, Siedling, R, Syben, O, Tenbusch, F, Toporowski, M, Xiao, W.J
• Format: Article
• Language: English
• ISSN: 0168-9002; 1872-9576
• DOI: 10.1016/S0168-9002(98)00093-X

GaAs strip and pixel detectors constructed in Aachen have been tested in a 1.4 GeV electron beam in Bonn and in a 5 GeV electron beam at DESY in February and May 1997. The strip detectors had a pitch of 50μm with a strip width of 25μm and were made of a 250μm thick Freiberger SI-GaAs wafer. The strip detectors included a punch-through bias structure and an integrated coupling capacitor. Additionally, an improved backside contact was formed, allowing a safe operation of the detector in a soft breakdown regime. Using the fast PreMux 128 preamplifier multiplexer chip ( τ p = 50 ns) a signal-to-noise ratio of 13 was obtained at normal beam incidence for a bias voltage of 200 V, leading to a spatial resolution of 11 μm with a simple COG algorithm. The 8 × 16 pixel array with a pixel size of 125 × 125 μm 2 was read out with the PreMux128 as well. With a double-metal technique, it was possible to bond the single-pixels linearly to the amplifier chip. The obtained signal-to-noise ratio of 30 in combination with a COG algorithm lead to the digital resolution value of 36 μm for both pixel coordinates.