Seiconductor diodes - Introduction

INTRODUCTION :
A semiconductor diode, the most common type today, is a crystalline piece of semiconductor material with a p–n junction connected to two electrical terminals.

However, diodes have a more complicated behavior than a simple on–off action. Semiconductor diodes begin conducting electricity only if a certain threshold voltage or cut-in voltage is present in the forward direction. The voltage drop across a forward-biased diode varies only a little with the current, and is a function of temperature.

Semiconductor diodes' nonlinear current-voltage characteristic can be tailored by varying the semiconductor materials and doping, introducing impurities into the materials. These are exploited in special-purpose diodes that perform many different function (eg: diodes are used to regulate voltage, to generate radio frequency oscillations, and to produce light). Tunnel diodes exhibit negative resistance, which makes them useful in some types of circuits.

Diodes were the first semiconductor electronic devices. The first semiconductor diodes (made in 1906) were made of mineral crystals such as galena, and nowadays they are made of sillicon.