The growth and properties of GaN:As layers prepared by plasma-assisted molecular beam epitaxy

We have studied the growth and properties of GaN:As layers prepared by molecular beam epitaxy, using a plasma source for active nitrogen. We have demonstrated that arsenic doping during growth produces films showing blue emission at room temperature. The blue emission is centred at 2.6 eV and is more than a decade stronger than the band edge emission. The films are predominantly wurtzite, but with a small cubic content which exists mainly close to the substrate-epilayer interface. We have investigated the influence of growth conditions on the intensity of this blue emission. In films grown under optimum conditions, the blue emission is strong enough to be clearly visible under normal room lighting. We have also discussed the transition from As-doped GaN showing blue emission to the formation of GaN 1- x As x alloys. We have determined that for a fixed arsenic flux, increasing the N/Ga ratio leads to the formation of alloy films. Our results suggest that this materials system may have potential applications in electronic and opto-electronic devices.