Chapter 24, Problem 24.46QP

Interpretation Introduction

Interpretation:

The semiconductor band gap energy determines the color of an LED. Knowing the energies of photons of different colors of light, which semiconductor would have the larger band gap: the one in a green exit sign’s LEDs, or the one in a red traffic signal has to be explained

Concept Introduction:

Semiconductors are substances that conduct electricity either by addition of an impurity or by the effects of temperature on it.  Semiconductors electrical conductivity lies between conductor and insulator.  Semiconductors have small energy gap between valence band and conduction band.

Addition of impurity to a semiconductor is termed as doping.  Doping alters the conductivity of a semiconductor.  The addition of an element having either more or less number of valence electrons than the natural semiconductor decides the combination as the following two types of semiconductor.

• n- type semiconductor
• p-type semiconductor

The combination of these two semiconductors finds application in solar cell and in diodes