Silicon Detector Some characteristics of silicon crystals conductance band Small band gap Eg=1.12 eV In a pure intrinsic (undoped )material the →W(e- h pair)=36eV electron density n and High specific density 2. 33 g/cm3 hole density p are valence equal n=p=n dEldx (M.I. P )=3.9 Mevcm ≈102e-h/pm( average) For silicon n a 145 1010 cm High carrier mobility He =1450cm/Vs In this volume Fh=450 cm2/Vs we have 4.5-10 free charge carriers, but only 3.2. e-h fast charge collection(<10 ns) pairs produced by a MP Very pure 1 ppm impurities Rigidity of silicon allows thin self Most detectors make use of supporting structures reverse biased p-n junctions Detector production by microelectronic techniquesSilicon Detector Some characteristics of Silicon crystals • Small band gap Eg = 1.12 eV ⇒ W(e-h pair) = 3.6 eV • High specific density 2.33 g/cm3 dE/dx (M.I.P.) ≈ 3.9 MeV/cm ≈ 102 e-h/µm (average) • High carrier mobility µe =1450cm2 / V.s, µh = 450 cm2 / V.s ⇒ fast charge collection (<10 ns) • Very pure < 1ppm impurities • Rigidity of silicon allows thin self supporting structures • Detector production by microelectronic techniques