Question

Problem #3: 3.6. A diode has wdo = 0.4 µm and φj = 0.85 V. (a) What reverse bias is required to triple the depletion-layer width? (b) What is the depletion region width if a reverse bias of 7 V is applied to the diode?

Answer 1

a) 6.8 Volt

b) 1.21Цm

Step-by-step explanation:

We are given from the question that

The zero -bias depletion layer width(
`W_(do)`) is 0.4Цm

The built in voltage φj is 0.85V

Now to calculate the reverse voltage(
`V_(R)`) that would be required to triple the depletion - layer width.

The depletion - layer width (
`W_(d)`) of the diode has the formula

`W_(d) = W_(do) \sqrt{1 + (V_(R) )/(Qj) }`

For three times of
`W_(d)` we have

`3W_(d) = W_(do) \sqrt{1 +(V_(R) )/(Qj) }`

=>
`(V_(R) )/(Qj) = 3^(2) -1`

=>
`V_(R) = 8Qj`

Substituting value of φj

We have

`V_(R) = 8(0.85V)`

= 6.8 V

The required bias voltage
`V_(R)` is 6.8 V

The solution for the b part of the question is uploaded on first image