Draw a graph illustrating how resistivity varies with temperature for an intrinsic semiconductor.

b) Gallium nitride, GaN, has an energy gap of 3.36 eV at 300 K. Calculate the wavelength of the light emitted by a GaN LED at this
temperature.
 
c) State the standard SI units for:

(i) mobility

(ii) diffusion coefficient (or diffusivity)

(iii) current density.
 
d) The p-type side of a pn junction diode is at a potential of -0.4 V and the n-type side at a potential of +0.3 V. A hole moves from the n-type side to the p-type side. What is the change in the potential energy of the hole in electron volts?

e) State three advantages of ion implantation over diffusion, as a means of introducing additional dopant into a wafer.

f)  Explain why the gate current in an MOS transistor is extremely small and give a typical value for this current. 
g)  The terminal voltages for an n-channel enhancement MOS transistor with VT = 0.5 V are:

VG = 5 V

VS = 3 V

VD = 4 V

Determine whether the channel in the device is pinched off in this situation.