Test: Electronic Devices - 6 - Electronics and Communication Engineering (ECE) MCQ

Smaller is the wave length used in lithography, better is the resolution.

Among the given options, x-rays have minimum wavelength and are expected to give best resolution.

Note: X-rays are presently not used because of increased cost associated while using them.

Given,

V_OC = 0.7 V, I_SC = 50 mA

Drawing equivalent circuit

The electron travelling from -15eV state to -5eV state radiate 10 eV energy as photon whose wavelength λ is given by

= 124.2 nm

The maximum power delivered P_m = V_m. I_m = f.f × V_OC­ I_SC

= 0.8 × 0.9 × 10 mA

= 7.2 mW

The smallest feature is limited by two Basic limits

a. Smallest Image that can be projected on water.

b. Resolving capability of photo resist

The current generated I = R.W

R = sensitivity

W = light power incident

I = 0.65 × 10^-2 × 20 mW/cm²

= 0.65 × 10^-2 × 10

= 0.13 mA

Output voltage form inverting Op-Amp

V_o = -0.13 × 10^-3 × 50 × 10³

= -6.5 V

• To speed the diffusion, process the wafer has to be heated at 1000°C. Thus, the mask used should have high meting point and hence hard masks of oxide & nitrides are used.
• Thermal diffusion cannot be used at later stages of the fabrication process because there could be a number of layers that might not be able to withstand high temperature.

Current generated I = P₀ × R

Given P₀ = 4 mw

Responsivity  

⇒ η ≃ 0.443

Oxidation:
- Oxidation of SI water to form SiO₂
- Acts as barrier for diffusion of impurities and contamination
- Can be used to fix shape of transistor

Epitaxial growth:
- A layer is built on substrate (n-type layer on p-type substrate and vice versa)
- All active ξ passive components, like transistor, bias resistors and diodes are fabricated on this layer.

Diffusion:
- Dopant impurities are diffused onto epitaxial layer to form terminals of transistor like, drain, source, gate etc.
- N-well, P-well are created using this process.
- Done at high temperature
- Depth of diffusion dependant on time of diffusion
- I_on implantation is also used for adding dopants, but the method is by bombarding Si wafer with accelerated ions.

Metallization:
- A thin metal (mostly aluminium) layer is added to form interconnection of components and Ohmic contacts

The external quantum efficiency is given by the relation

η_s = 3.6

η_a = 1

η_ext = 0.0193

Out of every 100 photons generated in Ga – As, only 1.93 are emitted out of the specimen.

for 500 photons → 9.5 emitted

Taking greatest integer value

[9.5] = 9