Time-Resolved Raman Studies of Wide Bandgap Wurtzite GaN

The recent surge of activity in wide-bandgap semiconductors [ 1 ] has arisen from the need for electronic devices capable of operation at high power levels, at high temperatures and in caustic environments, and separately, from a need for optical materials, especially emitters, that are active in the blue and UV wavelengths. Electronics based on existing Si and GaAs semiconductor device technologies cannot tolerate greatly elevated temperatures or chemically hostile environments. The wide-bandgap semiconductors with their excellent thermal conductivities, large breakdown fields, and resistance to chemical corrosion will be the materials of choice for these applications. Among the wide-bandgap semiconductors, the III—V nitrides have long been viewed as a very promising semiconductor system for device applications in the blue and UV wavelengths. The wurtzite polytypes of GaN, A1N, and InN form a continuous alloy system whose direct bandgaps range from 1.9eV for InN, to 3.4 eV for GaN, to 6.2 eV for A1N. Thus, III-V nitrides could potentially be fabricated into optical devices that are active at wavelengths ranging from the red all the way into the UV. Because of lower ohmic contact resistances and larger predicted electron saturation velocity [ 2 ] research in GaN is of particular interest.