optional blocking layer 12 were each inspected by one or more of the methods described above photoluminescence measurements were used to quantify band edge luminescence hall effect measurements to quantify electron mobility and concentration and x ray diffraction xrd to qualitatively assess the microstructure band edge luminescence and xrd were used to estimate band gap energy and lattice constants photoconductivity spectra measurements from visible to uv via methods understood in the art were used to reveal defect states within band gaps and surface recombinations contacts 9 a and 9 b were provided on first conducting layer 4 and second conducting layer 8 respectively to facilitate ohmic contact between the mentioned layers and leads 11 a and 11 b the surface of both first conducting layer 4 and second conducting layer 8 were etched using reactive ion etching in a chlorine plasma a method known within the art to expose the underlying n type gan layer a conductive metal preferably a double layer gold titanium film was thereafter deposited onto the exposed surface via evaporation also a method understood in the art contacts 9 a and 9 b may be annealed after deposition to improve their contact properties the etch process may include photoresist methods understood in the art for example a photoresist mask may be applied onto selected surface regions of the second conductive layer 8 thereafter a chlorine based plasma is used to etch the unmasked regions of the gan to expose an.