Heterojunction Lasers - Definition, Construction, Working, Advantages, Disadvantages and Applications: The device described in previous section was the first type employed in the early development of semiconductor lasers. It is known as an homojunction laser…
Light Emitting Materials: Since the eye is only sensitive to light of energy hf ≥ 1.8 eV (~ 0.7 μm), semiconductors of interest must have energy band gaps larger than this limit. The band gaps of…
IR Emitters or Infrared-emitting diodes: IR Emitters or Infrared-emitting diodes are solid-state gallium arsenide devices that emit a beam of radiant flux when forward biased. Fig. 25.53 depicts the basic construction of the device. When…
Photoemissive cells or Tubes - Working Principle and Types: These Photoemissive cells or Tubes devices are basically of two types namely vacuum type and gas filled type. 1. Vacuum Type Photocell (or Phototube): This device essentially…
Avalanche Photodiode - Definition, Basic Structure and Workings: The avalanche photodiode is similar to the P-N or PIN photodiode except that it is operated at high reverse-bias voltages so that impact ionization occurs, EHPs are…
Pin Photodiode - Definition, Working and Applications: The PIN photodiode is one of the most common photodetectors, since the depletion-region thickness (intrinsic layer) can be tailored to optimize the quantum efficiency and the frequency response.…
Light Dependent Resistors (LDRs) - Definition, Construction, Workings and Applications: Light dependent resistors (LDRs) are made from cadmium sulphide containing no or very few free electrons when not illuminated. Its resistance is then quite high.…
Photodetectors - Definition and Applications: Photodetectors are the semiconductor devices that can detect optical signals through electronic processes. The extension of coherent and incoherent light sources into the far-infrared region on one hand and the…
Photoconductivity - Definition, Working and its Applications: Photoconductivity - When excess electrons and holes are produced in a semiconductor, there is a corresponding increase in conductivity of a sample as indicated by the following equation…
Luminescence - Definition and Types: When a system absorbs energy in some form or other, it may be partly re-emitted as radiation. This phenomenon is called luminescence. Luminescence may occur in solids (crystals or glasses)…
