TABLE OF CONTENTS Semiconductor optoelectronic devices based on the concepts discussed in the previous section have led to many important technologies. These include image display, optical communication, optical information storage, desktop printing, bar code reading, etc. Semiconductor devices have also been used to demonstrate logic functions and to implement sophisticated mathematical algorithms. However, optical computing is not yet a commercial technology. Semiconductor energy conversion devices (solar cells) have also found niche markets, but due to mostly market forces and politics, they are not a major force in global energy markets. But advances in solar cell fabrication (including the potential use of organic solar cells), along with environmental concerns may gradually make semiconductors a dominant force in addressing the energy needs of the world.
An area where semiconductor light-emitting diodes (LED) can have a major impact is in the lighting market. The LED, a device with a far greater lifetime and efficiency, can in principal, replace the light bulb that currently dominates this industry.
We have seen in Section 5.3 that when light impinges on a semiconductor with photon energy larger than the bandgap, electron-hole pairs are generated. If the electron-holes can be swept away to create an electrical signal (a current or a voltage) we can have a detection or energy conversion device. A device structure in which the photogenerated electrons and holes can be collected is the p-n diode. A metal-semiconductor junction can also provide a structure for a detector,...
