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A thin film resistor is to be made from a GaAs film doped n-type. The resistor is to have a value of 2 kΩ. The resistor length is to be 200 µm and area is to be 10–6 cm2. The doping efficiency is known to be 90%. The mobility of electrons is 8000 cm2/ V–s. The doping needed is—
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- 8.7 × 1015 cm–3
- 8.7 × 1021 cm–3
- 4.6 × 1015 cm–3
- 4.6 × 1021 cm–3
Correct Option: A
Given data, R = 2 kΩ = 2000 Ω
L = 200 µm = 200 × 10–4 cm
A = 10–6 cm2
n0 = .9 Nd
Now from relation
| R = | ⇒ n0 | n0q·µnA | RqµnA |
| .9 Nd = | 2000 × 1.6 × 10–19 × 8000 × 10–6 |
or Nd = 8.7 × 1015 cm–3
Hence alternative (A) is the correct choice.
