212 CHAPTER 4. JUNCTIONS IN SEMICONDUCTORS:P-NDIODES
Problem 4.3Give a short discussion on why the reverse-bias current in an idealp-ndiode
has no voltage dependence. Discuss also the voltage dependence of the reverse-bias
current in a non-ideal diode (i.e., a diode with defects).
Problem 4.4Consider a Si short (or narrow)p-ndiode with the following parameters:
n-side thickness =3. 0 μ/m
p-side thickness =4. 0 μ/m
n-side doping =10^18 cm−^3
p-side doping =10^18 cm−^3
minority carrier lifetimeτn = τp=10−^7 s
electron diffusion constant =30cm^2 /s
hole diffusion constant =10cm^2 /s
diode area =10−^4 cm^2 /s
Calculate the diode current at a forward bias of 0.5 V at 300 K. Also calculate the total
excess hole charge (in coulombs) injected into then-side (fromWnto the dioden-side
contact) at this biasing.
Problem 4.5Consider a Si longp-ndiode with the following parameters:
n-side doping =10^18 cm−^3
p-side doping =10^18 cm−^3
minority carrier lifetimeτn = τp=10−^7 s
electron diffusion constant =30cm^2 /s
hole diffusion constant =10cm^2 /s
diode area =10−^4 cm^2 /s
Calculate the diode current at a forward bias of 1.0 V at 300 K.
An electron comes from thep-side into the depletion region and is swept away by the field
to then-side.Estimatethe time it takes the electron to crossthedepletionregion at zero
applied bias and a reverse bias of 1.0 volt.
Problem 4.6Consider a Si longp-ndiode with the following parameters:
n-side doping =10^17 cm−^3
p-side doping =10^17 cm−^3
minority carrier lifetimeτn = τp=10−^7 s
electron diffusion constant =30cm^2 /s
hole diffusion constant =10cm^2 /s
diode area =10−^4 cm^2
carrier lifetime in the depletion region =10−^8 s
