Excimer laser annealing effects on AlGaN/GaN heterostructures

We investigated impact of excimer laser annealing on the AlGaN/GaN heterojunction structures, where the 2-dimensional electron gas (2DEG) is formed. When applying homogeneous laser pulses at various laser densities, the electrical resistance of the 2DEG shows sudden increase along with sharp decrease of the carrier mobility and slight decrease of the carrier density. Especially, when applying laser density of 300 mJ/cm², we could obtain such jump of electrical resistance even after 2 min, i.e. 2400 pulses at 20 Hz. Low temperature photoluminescence and x-ray photoemission spectroscopy measurements show that the excimer laser annealing suppresses the coherent charge carriers and oxides the sample surface to form Ga₂O. We estimate the activation energy of suppressing 2DEG to be 0.89 eV for the ELA process. We suggest that the excimer laser annealing has potential for gate oxide fabrication, surface passivation, and lateral pattering of 2DEG structures.