Raman and PL Characterization of GaN

Gallium Nitride (GaN) is one of a generation of promising light-emitting materials. Its direct energy band gap of ~3.4 eV at room temperature make it particularly suitable for emission in the blue, and near UV spectral ranges. The material often exhibits high temperature stability and low electrical leakage, and hence GaN is generally a good candidate for fabricating high-temperature and high-power devices.

High quality GaN is relatively difficult to produce with GaN bulk crystals difficult to obtain under many conditions. Improvements in the surface morphology and in the electrical and optical properties can be provided with the use of modified production procedures such as a buffer layer. However, GaN does not always grow uniformly. The films may contain a large number of extended defects and exhibit a non ideal behavior, for example a high background donor concentration can lead to problems for reproducible doping. Eg. For p-type dopant inclusion

Therefore, In order to produce better devices with higher output efficiencies and greater longevity, it is important to understand how GaN growth proceeds, how the numbers and types of defects evolve during growth and what are the roles of the buffer layers and modified production regimes.

Micro Photoluminescence (PL) and micro Raman analysis provided by the LabRAM HR are an important tool for the characterization of GaN materials.

This instrument allows the user to study many of the important properties of GaN and other semiconductor samples and hence to understand better the material.

The automated acquisition capabilities enable a PL and Raman spatial map to be obtained. Where defects and discontinuities on a 1 um scale can be observed.

The unique high resolution Raman data provided by the instrument enables detailed investigations of stresses in the film, crystallographic orientation, and of free carrier concentration.

The broader band PL characterization of emission bands, particularly at low temperature, reveals the effect of defects in the material and other such electronic and optical details.

The figure below shows the Raman and PL spectrum of GaN taken with a 325nm laser excitation on the LabRAM HR.

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