Semiconductor Fundamentals and Integrated Circuit Technology

Light Emitting Diodes (LEDs)

LEDs function through a complex chemical process where electrons emit photons as they return to their valence orbits.

Types of Electronic Components and Circuits

Discrete Devices

Discrete devices are electronic components manufactured separately with wire leads for connection to a full circuit. These components are typically installed on printed circuit boards alongside other electronic elements.

Monolithic Integrated Circuits

In a monolithic integrated circuit, all circuit components are contained within a single silicon chip. The conductors and insulators are formed through chemical gas reactions and the deposition of metals such as aluminum.

Digital Integrated Circuits

Digital integrated circuits produce signals with two distinct voltage levels. They are constructed from simple building blocks called gates, which act as electronically controlled switches that can be either on or off.

Hybrid Circuits

A hybrid circuit is built using several different devices and multiple integrated circuits. These can utilize either thin film or thick film technology.

Extrinsic Semiconductors and Doping

Extrinsic semiconductors are characterized by a small percentage of impurities relative to the intrinsic material. This process involves adding trivalent or pentavalent elements, a technique known as doping.

N-Type Extrinsic Semiconductors

N-type extrinsic semiconductors are doped with pentavalent elements such as Arsenic (As), Phosphorus (P), or Antimony (Sb). Because these elements have five electrons in their outer layer, the resulting crystal structure contains an electron that is not part of any covalent bond, placing it at a higher energy level. Due to thermal energy, these electrons are released and are no longer bound to the semiconductor. In N-type materials, electrons are the majority carriers, and the impurities are called donors.

P-Type Extrinsic Semiconductors

P-type extrinsic semiconductors are doped with trivalent elements such as Aluminum (Al), Boron (B), Gallium (Ga), or Indium (In). Having only three valence electrons creates a vacancy (or hole) with an energy level slightly above the valence band. This allows electrons to easily jump into the vacancy, leaving holes in the valence band. Consequently, holes are the majority carriers in P-type materials.

Voltage and Threshold Characteristics

Threshold Voltage: This is the specific voltage required to drive an LED. The step area occurs when the applied voltage exceeds this threshold.

Electrical Formulas:

• Vdc = 0.45 × Vac (Charge)
• Vmax = 1.44 × Vac (Reverse Diode)