Semiconductor Junctions

By combing doping and semiconductor material, many different semiconductor junctions can be formed. If more than one type of semiconductor forms the junction region, the semiconductor is known as a heterojunction and in many semiconductor devices thesedifferent junctions are vital or lead to ehanced performance of the device.

When two semiconductors with different energy gaps are combined, a heterojunction is formed. The most important difference between these semiconductors in heterostructure devices is the energy gap and refractive index. Also, the threshold current density was improved at room temperature and it was achieved by cladding the active layer material, such as GaAs, with wider energy gap material, for instance Al _x Ga _1-x As has very good lattice constant matching with GaAs. In general, heterostructure lasers will give you both good optical and current confinement, such as P-n-N or P-p-N double heterostructure laser. The conductivity type of the smaller energy gap crystal is denoted by a lower case n or p and that of the larger energy gap crystal is denoted by an upper case N or P.

On these pages we shall examine more closely the theory of Heterostructures and attempt to model their behaviour using the software developed by J. Wah. of Essex University's Optoelectronics Research Group to run in a friendly Matlab GUI.