J.-C. Pesant

Raman characterization of Mg+ ion-implanted GaN

Mg+ ions were implanted at room temperature in n-type hexagonal GaN for the device isolation purposes. The implantation dose varied from 7.5 × 1012 to 1016 ions cm−2. We performed resonance Raman spectroscopy and DC electrical measurements in order to monitor the structural and electrical changes of non-annealed and annealed implanted GaN samples. Annealing was carried out at 900 °C for 30 s, these conditions being used to achieve good Ohmic contacts. The aim was to determine, on the one hand, the influence of ion doses on the device isolation and, on the other, to establish the order of the technological steps which should be made between ion implantation and Ohmic contact annealing. On increasing the implantation dose from 7.5 × 1012 to 2 × 1014 ions cm−2, an increase in the electrical isolation and a decrease in the photoluminescence (PL) were observed. For the highest dose, the implanted layer became conductive owing to a hopping mechanism and only the first-order phonon lines remained observable. After annealing, the implanted samples became conductive and the PL reappeared or increased compared with the non-annealed samples at same implantation doses, except for the sample implanted at the highest dose, which became insulating. Then, it is possible to achieve device electrical isolation by using a lower ion dose without thermal annealing or using a higher ion dose with thermal annealing.

Raman characterization of GaN synthesized by N implantation in GaAs substrate

GaN material was synthesized by implantation of N ion into a GaAs (001) semi-insulating substrate. After implantation, different annealing treatments were applied and the results were investigated using UV Raman spectroscopy. More particularly, temperature and time treatments ranging between 500 and 950 °C and 1 and 20 min, respectively, were studied. The results of these studies showed that, by using appropriate annealing conditions, a high-quality GaN crystalline layer can be obtained on GaAs substrates. Copyright

Resonant Raman scattering study of Ar+ ion-implanted AlGaN

160 keV Ar+ ions were homogeneously implanted in AlGaN at room temperature for device isolation purposes. Resonance Raman spectroscopy and DC electrical measurements were used to monitor the structural and electrical changes of the non-annealed and annealed implanted AlGaN samples with a dose ranging from 3.4 × 1012 to 1 × 1016 ions cm−2. The annealing was carried out at 900 °C for 40 s, these conditions being necessary to achieve good Ohmic contacts. On increasing the implantation dose from 3.4 × 1012 to 3.4 × 1014 ions cm−2, an increase in the electrical isolation and a decrease in the photoluminescence (PL) were observed. For the highest dose, the implanted layer becomes conductive, probably due to a hopping mechanism. After annealing, the implanted samples become conductive and the PL reappears or increases as compared to the non-annealed samples using the same implantation doses. Then, it is possible to obtain good device electrical isolation by implanting ions with a 3.4 × 1014 cm−2 dose subsequently to the annealing process necessary to achieve Ohmic contacts.