Basic Electronics
BASIC DIODE ELECTRONICS
INTRODUCTION TO DIODES
The p-n Junction The p-n junction is a homojunction between a p-type and an n-type semiconductor. It acts as a diode, which can serve in electronics as a rectifier, logic gate, voltage regulator (Zener diode), switching or tuner (varactor diode); and in optoelectronics as a light-emitting diode (LED), laser diode, photodetector, or solar cell. In a relatively simplified view of semiconductor materials, we can envision a semiconductor as having two types of charge carriers-holes and free electrons which travel in opposite directions when the semiconductor is subject to an external electric field, giving rise to a net flow of current in the direction of the electric field. Figure 1 illustrates the concept.
A p-n junction consists of a p-type and n-type section of the same semiconductor materials in metallurgical contact. The p-type region has an abundance of holes (majority carriers) and a few mobile electrons (minority carriers); the n-type region has an abundance of mobile electrons and a few holes (Fig. 2). Both charge carriers are in continuous random thermal motion in all directions.
Fig. 2. Energy levels and carrier concentrations for a p-type and n-type semiconductor before contact.
1
When a section of p-type material and a section of n-type material are brought in contact to form a pn junction, a number of interesting properties arise. The pn junction forms the basis of the semiconductor diode. Electrons and holes diffuse from areas of high concentration toward areas of low concentration. Thus, electrons diffuse from the n-region to the p-region., leaving behind positively charged ionized donor atoms. In the p-region the electrons recombine with the abundant holes. Similarly, holes diffuse from the p-region into the n-region, leaving behind negatively charged ionized acceptor atoms. In the n-region the holes recombine with the abundant mobile electrons. This diffusion process does not continue
INTRODUCTION TO DIODES
The p-n Junction The p-n junction is a homojunction between a p-type and an n-type semiconductor. It acts as a diode, which can serve in electronics as a rectifier, logic gate, voltage regulator (Zener diode), switching or tuner (varactor diode); and in optoelectronics as a light-emitting diode (LED), laser diode, photodetector, or solar cell. In a relatively simplified view of semiconductor materials, we can envision a semiconductor as having two types of charge carriers-holes and free electrons which travel in opposite directions when the semiconductor is subject to an external electric field, giving rise to a net flow of current in the direction of the electric field. Figure 1 illustrates the concept.
A p-n junction consists of a p-type and n-type section of the same semiconductor materials in metallurgical contact. The p-type region has an abundance of holes (majority carriers) and a few mobile electrons (minority carriers); the n-type region has an abundance of mobile electrons and a few holes (Fig. 2). Both charge carriers are in continuous random thermal motion in all directions.
Fig. 2. Energy levels and carrier concentrations for a p-type and n-type semiconductor before contact.
1
When a section of p-type material and a section of n-type material are brought in contact to form a pn junction, a number of interesting properties arise. The pn junction forms the basis of the semiconductor diode. Electrons and holes diffuse from areas of high concentration toward areas of low concentration. Thus, electrons diffuse from the n-region to the p-region., leaving behind positively charged ionized donor atoms. In the p-region the electrons recombine with the abundant holes. Similarly, holes diffuse from the p-region into the n-region, leaving behind negatively charged ionized acceptor atoms. In the n-region the holes recombine with the abundant mobile electrons. This diffusion process does not continue