Electrical properties of GaN layers grown by metal organic vapor phase epitaxy (MOVPE)

The electrical properties of three un-doped GaN samples grown at low pressure by Metal Organic Vapor Phase Epitaxy (MOVPE) on sapphire substrates are reported. Two different growth temperatures of 900°C and 950°C were used, for 90 min. Also, two trimethylgallium flow fluxes were set (5.39 μmole/minute and 8.39 μmole/minute). The temperature dependent Hall (T-Hall) technique was used, between 35 K and 373 K. The resistivity of our samples fluctuated between 3 and 24mΩ×cm. They were temperature dependent and were explained by two thermally activated processes, with activation energies of 20 and 70 meV. For the two samples grown at 900°C, the mobilities and the charge carrier densities were temperature independent with values of 10 and 20cm ²V ^-1s ^-1, and 6×10 ¹⁹ and 5×10 ¹⁹cm ^-3, respectively. For the sample grown at 950°C, the mobility showed temperature dependence to the power of +1/3 and the charge carrier density a thermally activated dependence with an activation energy of 5 meV.