• lateral p-n junction

This project has been realized at the Nano-Science-Center of Copenhagen.
The scheme, analyzed in this thesis, is a new lateral p-n diode on GaAs,
with an undoped single quantum well AlGaAs(p-type)/GaAs/AlGaAs. Part
of the sample is etched away forming a MESA island and the n-, p- and the
back-gate contacts are made with different metal layers. That one with the
substrate is to control the gate voltage,while the n- and p- type of contacts to
apply the bias to the junction.
In the p-region of the GaAs quantum well a two dimensional gas of holes (2DHG) is confined, due to a p-doped layer.
A two dimensional gas of electron (2DEG) appears in the n-region of the QW when a gate
voltage is applied. So, 2D-gases can be recombined and can determine the
emission of light, in the infrared, from the junction. The light can be measured with the use of an experimental
setup, based on an optical cryocooler, which allows us to work with electroluminescence at low temperature (about
8K). Firstly, for a complete study of the structure, an electrical characterization of the device has been made and, confornting with other results, a high value of the carriers mobility has been found.

This thesis is divided into three chapters.
In the first chaptre there is a theoretical
introduction about the quantum well and optical recombination; they are the
basic information to the next study.
The second chapter contains the description of the sample fabrication, its
basic characteristic, and the adopted measuring system .
The third chapter reports both the electrical and optical measurement realized in laboratory and the achieved results .
The appendix shows the basic operation, followed to cool down
the cryostat .