The Pt/Ga<sub>2</sub>O<sub>3</sub>/GaN diodes were fabricated in which the Ga<sub>2</sub>O<sub>3</sub> oxide layers were directly grown on GaN layer using a photoelectrochemical method. Then, the Ga<sub>2</sub>O<sub>3</sub> oxide films were annealed in O<sub>2</sub> ambiance at 700 °C for 2 hours to perform the β-Ga<sub>2</sub>O<sub>3</sub> crystalline phases. The hydrogen sensing characteristics of Pt/GaN (metal-semiconductor, MS) and Pt/β-Ga<sub>2</sub>O<sub>3</sub>/GaN (metal-insulator-semiconductor, MIS) diodes under hydrogen-containing ambiance were studied in an air atmosphere. Compared with the MS devices, the MIS devices exhibited better hydrogen sensing ability. The result demonstrates that the β-Ga<sub>2</sub>O<sub>3</sub> layer plays an important role in the hydrogen sensing of the GaN based MIS diodes.
The co-sputtering Al-doped ZnO (AZO) films with Al nano-particles were used to increase the extraction efficiency of
GaN-based light-emitting diodes (LEDs). Fixing the ZnO radio frequency (RF) power of 100W and changing the Al DC
power from 0 to 13W, the AZO films with various Al contents can be obtained. In the experimental results, the AZO
films deposited with Al DC power of 0, 4.5 and 7W do not have Al segregation. However, the segregated Al
nano-particles can be found in the AZO films deposited by Al DC power of 10W and 13W. The co-sputtering 170
nm-thick AZO films with and without Al nano-particles were deposited on the transparent area of LEDs and compared
the light output intensity of conventional LEDs. The light intensity of LEDs with AZO films with Al DC power 0, 4.5
and 7W increased 10% than that of conventional LEDs. This was due to the AZO film played a role of anti-reflection
coating (ARC) layer. The light intensity of LEDs with AZO film deposited using Al DC power of 10W and 13W
increased about 35% and 30%, respectively. It can be deduced that the output light is scattered by the Al nano-particles
existed in the AZO film.
A chlorination surface treatment was used to reduce the surface states of an n-type GaN surface, which improves the Schottky performances of the resultant metal-semiconductor contact. At a reverse bias of 10V, the dark current of the GaN-based UV-PDs with and without chlorinated surface treated were 28.1nA and 0.59μA, respectively. The dark current of chlorine-treated Schottky UV-PDs was 21 times of magnitude smaller than that of those without chlorination treatment. The product of quantum efficiency and internal gain of the GaN Schottky UV-PDs without and with chlorination treatment under a reverse voltage of 10V at a wavelength of 330nm was 650% and 100%, respectively. The internal gain of chlorine-treated GaN UV-PDs can be reduced due to the improvement of surface state density.