Practical laser action in this type of system can be achieved through double heterostructure injection. They are characterized at low temperatures by a full valence band that is separated from an unoccupied conduction band by an energy gap, and thus excited states can be created through thermal fluctuations and applied voltages. Essential to the creation of light emitting 
Practical laser action in this type of system can be achieved through double heterostructure injection. They are characterized at low temperatures by a full valence band that is separated from an unoccupied conduction band by an energy gap, and thus excited states can be created through thermal fluctuations and applied voltages. Essential to the creation of light emitting diodes and transistors, FTP, what are these materials, which include germanium and silicon, with electrical resistivities between those of insulators and conductors?
Practical laser action in this type of system can be achieved through double heterostructure injection.
{Semiconductor}