We consider - at first (part a) and b)] - a undoped GaAs crystal at room temperature (T = 300 Kor KT = 25,9 meV). The effective state densities and the gap energy are given by: Nc = 4,45.1017 cm, P = 7,72 1018 cm-", E, = 1,42 eV Use for the following calculations the equations (see formula overview) which are based on the Boltzmann-approximation. a) Calculate the electron density, the hole density and the intrinsic density ni. b) Where is in the intrinsic case the Fermi-level Ef located (not in words but numerically in the unit meV, still at T = 300 K), relatively to the conduction band edge and the valence band edge, re- spectively? c) Now we increase the electron density by the help of doping (extrinsic case, exhaustion region): n = 1016 cm. How big is then the hole density and where lies the Fermi-level (not in words but numerically in the unit meV, still at T = 300 K), relatively to the conduction band edge and the valence band edge, respectively