Homework #1 - due Thursday, 17 February 2005, in class

1. A Ge sample is uniformly doped with 5E16 atoms cm^-3 of indium acceptors.  Assume that all the atoms are ionized and take n_i = 2E13 cm^-3 at T=290K.  Calculate the electron and hole concentrations in the sample.

2.   A uniformly doped Si sample has a donor concentration of 5E15 cm^-3 and an acceptor concentration of 1.1 E16 cm^-3. (a) Calculate n_o and p_o at 300 K and at 150 K.  Hint - for the temperature dependence, use n_i = 3.88E16T^3/2exp [-7000/T]cm^-3 for Si.  (b) if the sample if further doped with 4E15 donors cm^-3, calculate the new electron and hole concentrations at 300 K.

3. A GaAs sample is doped so that the electron and hole components of current are equal in an applied electric filed.  Calculate: (a) the equilibrium electron and hole concentrations, (b) the net doping and (c) the sample resistivity at 300 K.

4.  A sample of Ge has an intrinsic resistivity of 60 Ohm-cm.  Calculate the value of current density in an applied field of 10 mV cm^-1 if there are 1E13 donors cm^-3 and 4E12 acceptors cm^-3.  Take m_n = 4200 cm²V^-1sec^-1 and m_p = 2000 cm²V^-1sec^-1.  Assume that all the impurities are ionized.
 
 

  Homework assignments will appear on the web at: http://www.ece.udel.edu/~kolodzey/courses/eleg646s05.html
  Note: On each homework and report submission, you must please give your name, the due date, assignment number and the course number.