Question 3
Consider a silicon pn junction diode at room temperature with:
EG = 1.1 eV VBI = 950 meV
÷ = 4.0 eV
êS = 12
ND = 5x1017 cm-3 NA = 5x1018 cm-3
DP = 5 cm2/sec DN = 4 cm2/sec
The n-bulk region and p-bulk region are both short compared to the respective minority-carrier diffusion lengths, with lengths of WN and WP, respectively.
WN = WP = 100 nm
b) For small forward biases, we expect a non-ideal region with current ~ e qV/2kT. Explain the dominant conduction mechanism in this region, using appropriate diagrams as necessary.
c) For large forward bias, the current deviates from ideal due to potential drop across the bulk regions. For this part, you may assume that the current through the bulk region corresponds to drift current.
i) State whether the n-bulk or p-bulk has a larger voltage drop.
ii) Estimate the current density corresponding to a point where the actual current is 1/e times the ideal current (you can ignore the side with lower voltage drop).
d) Reverse-bias breakdown typically occurs at a critical field of EC=4x105 V/cm.
Calculate the reverse-bias breakdown voltage.
Attachment:- Question 3.docx