Homework 1
Due date – 27th Oct 2007
1. Consider a silicon pn junction at T=300K, ni = 1.5*1010 cm-3 .
Calculate the hole concentration at the edge of the space charge region
with a forward bias of 0.7 V is applied to the pn junction and n-doping
is 1.8*1010 cm-3 .
2. Consider an ideal pn junction diode at T=300K operating in forward
bias region. Calculate the change in voltage that will cause a factor of
ten increase in current.
3. To determine the ideal reverse saturation current density in a silicon
pn junction at T=300K. Consider the following parameters in a
silicon pn junction. Na=Nd=1018 cm-3, ni=1.6*1010 cm-3, Dn=25
τcmcm2/sec, Dp=10 cm2/sec, τcmp0= τcmn0=5*10-7 sec, εr=11.7 of silicon.
4. Calculate the applied reverse bias voltage at which the ideal reverse
current in a pn junction diode at T=300K reaches 90% of its reverse
saturation current value.
5. Calculate the electric field (E) required to produce a given majority
carrier drift current value. Consider a silicon pn junction at T=300K
with the parameters. Forward-bias Voltage Va =0.7 V
Na=Nd=1018 cm-3 , ni=1.6*1010 cm-3 , Dn=25 cm2/sec, Dp=10 cm2/sec,
τcmp0= τcmn0=5*10-7 sec, εr =11.7 of silicon. Given J=Jn=en Nd E, n=1350
cm2/V-sec
6. Explain the effects of temperature on the pn junction.
7. Write down the current voltage relationship of a pn junction and give
the expression of ideal reverse saturation current density. Plot the
ideal IV characteristics of a pn junction diode.