Читать книгу A Course in Luminescence Measurements and Analyses for Radiation Dosimetry - Stephen W. S. McKeever - Страница 34

(a) Consider an electron trap at energy E and energy depth Et = Ec – E (where Ec is the bottom of the conduction band). The total concentration of traps is N, of which n are filled with electrons. What will be the occupancy of this trap if E = EF?

(b) If Nc is the density of available states in the conduction band, nc is the concentration of free electrons, ve is the thermal velocity of free electrons, and σ is the capture cross-section for the trap, show that the attempt-to-escape frequency, s is given by Equation 2.3. (Hint: consider equilibrium between trap filling and trap emptying.)

(c) What is the expected T dependence of s?

(d) If me*≈mh*, show that, at thermal equilibrium at T > 0 K, the Fermi Level lies mid-gap.