Implantation induced electrical isolation of sulphur doped GaNxAs1−x layers

The study of III-N-V semiconductor alloys, especially GaNxAs1−x has been increasing in the last few years. The strong dependence of the band gap on the nitrogen content has made this material important for a variety of applications, including long wavelength optoelectronic devices and high efficiency solar cells. We report on the effects of sulphur doping implants on the achieved electrical isolation in GaNxAs1−x layers using proton bombardment. Sulphur ions were implanted in MOCVD-grown GaNxAs1−x layers (1.4 μm thick with nominal x = 1%) with multiple energies creating approximately uniform doping profiles in the range of about 1 × 1018-5 × 1019 cm−3. Several proton implants were performed in order to find the threshold dose (minimum dose to achieve maximum sheet resistivity) for the electrical isolation of n-type GaNxAs1−x layers. Results show that the sheet resistance of n-type layers can be increased by about five orders of magnitude by proton implantation and the threshold dose to convert a conductive layer to a highly resistive one depends on the original free carrier concentration. The study of annealing temperature dependence of sheet resistivity in proton-isolated GaNxAs1−x layers shows that the electrical isolation can be preserved up to 450 and 500 °C when the implantation is performed at RT and 77 K with threshold dose, respectively. These results for n-type GaNxAs1−x layers are novel and have ramifications for device engineers.