Physics and Engineering of Radiation Detection

276 Chapter 5. Solid State Detectors Because of the low band gap energy, intrinsic charge carrier concentration of germanium is ...

5.1. Semiconductor Detectors 277 T (K) 250 260 270 280 290 300 310 -3) (cmi n 1012 1013 Figure 5.1.17: Dependence of intrinsic c ...

278 Chapter 5. Solid State Detectors Some of the important electrical properties of germanium are listed in Table 5.1.7. Compari ...

5.1. Semiconductor Detectors 279 Figure 5.1.18: Dependence of electron drift velocity on elec- tric field intensity in germa- ni ...

280 Chapter 5. Solid State Detectors Figure 5.1.19: Dependence of electron mobility on absolute temperature in germanium (20). S ...

5.1. Semiconductor Detectors 281 Eg= 1.42 eV EX= 1.90 eV EL= 1.71 eV Wavevector Holes Energy Figure 5.1.20: Band structure dia ...

282 Chapter 5. Solid State Detectors where bothNcandNvare in units ofcm−^3. The energy gapsELandEXcorre- sponding toLandXvalleys ...

5.1. Semiconductor Detectors 283 Table 5.1.8: Mobilities (μe,μh,) velocities (ve,vh), and diffusion coefficients (De,Dh) of elec ...

284 Chapter 5. Solid State Detectors the reader, the direct consequence of low charge carrier lifetime is the loss of signal. Si ...

5.1. Semiconductor Detectors 285 wherexpdandxndare the widths of the depletion regions onp-andn-sides respec- tively,NAandNDare ...

286 Chapter 5. Solid State Detectors il il Depletion Region − − −− + − ++ + + p n i V (a) (b) ReverseBias ForwardBias − + Figure ...

5.1. Semiconductor Detectors 287 this value must be multiplied by the permittivity of free space 0 =8. 854 × 10 −^12 C^2 N−^1 m ...

288 Chapter 5. Solid State Detectors Similarly for the n-side we get E(x)=− dΦ dx = eND  (x−xn)for0≤x<xn (5.1.61) Fig.5.1.26 ...

5.1. Semiconductor Detectors 289 This expression can be used to determine the individual depletion depths provided we make use o ...

290 Chapter 5. Solid State Detectors whereμis the mobility of majority charge carrier andNis the dopant concentration. For the c ...

5.1. Semiconductor Detectors 291 dielectric constant is 12. Hence we have CA = [ eNA 2 V 0 ] 1 / 2 = [( 1. 602 × 10 −^19 ) (12) ...

292 Chapter 5. Solid State Detectors Hence according to Ramo’s theorem the induced current will be i = qμ V 0 d 1 d = qμ V 0 d^2 ...

5.1. Semiconductor Detectors 293 ie ih te th pn − − + x d 0 Q t (a) (b) 2q/3 q Figure 5.1.28: (a) An almost fully depleted p ...

294 Chapter 5. Solid State Detectors This shows that the hole takes approximately three times longer than the electron to reach ...

5.1. Semiconductor Detectors 295 I.1 PhotovoltaicMode....................... In this mode a very large load resistance is applie ...