Question

The electron concentration in a sample of uniformly doped n – type silicon at 3000 K varies linearly from 10^17/^3 = 0 6 × 10^16/^3 = 2. Assume a situation that electrons are supplied to keep this concentration gradient constant with time. If electronic charge is 1.6 × 10^-19 coulomb and the diffusion constant = 35 ^2/, the current density in the silicon, if no electric field is present is

Answer 1

Answer:

option d)

Explanation:

n

1

=10

17

/cm

3

x

1

=0

n_{2} = 6\times 10^{16}/ cm^{3} \:\:\:\:\:x_{2} = 2\mu mn

2

=6×10

16

/cm

3

x

2

=2μm

q = 1.6 \times 10^{-19}cq=1.6×10

−19

c

D_{n} = 35\, cm^{2}/D

n

=35cm

2

/ sec

J=qD_{n}\frac{dn}{dx}=1.6\times 10^{-19}\times 35\times [\frac{6\times 10^{16}\,-\,10^{17}}{2\times 10^{-4}}]J=qD

n

dx

dn

=1.6×10

−19

×35×[

2×10

−4

6×10

16

−10

17

]

J = – 1120\, A / cm^{2}J=–1120A/cm

2

Hence, the correct option is (d)