Gallium nitride (GaN) is a compound semiconductor that has tremendous potential to facilitate economic growth in a semiconductor industry that is silicon-based and currently faced with diminishing returns of performance versus cost of investment. At a material level, its high electric field strength and electron mobility have already shown tremendous potential for high frequency communications and photonic applications. Advances in growth on commercially viable large area substrates are now at the point where power conversion applications of GaN are at the cusp of commercialisation. The future for building on the work described here in ways driven by specific challenges emerging from entirely new markets and applications is very exciting. This collection of GaN technology developments is therefore not itself a road map but a valuable collection of global state-of-the-art GaN research that will inform the next phase of the technology as market driven requirements evolve. First generation production devices are igniting large new markets and applications that can only be achieved using the advantages of higher speed, low specific resistivity and low saturation switching transistors. Major investments are being made by industrial companies in a wide variety of markets exploring the use of the technology in new circuit topologies, packaging solutions and system architectures that are required to achieve and optimise the system advantages offered by GaN transistors. It is this momentum that will drive priorities for the next stages of device research gathered here.

Surface passivation effects were studied on AlGaN/GaN high-electron-mobility transistors (HEMTs) using SiO2, Si3N4, and silicon oxynitride (SiON) formed by plasma enhanced chemical vapor deposition. An increase of IDmax and gmmax has been observed on the passivated (SiO2, Si3N4 and SiON) HEMTs when compared with the unpassivated HEMTs. About an order of magnitude low IgLeak and three orders of magnitude high IgLeak was observed on Si3N4 and SiO2 passivated HEMTs, respectively, when compared with the unpassivated HEMTs. The increase of IgLeak is due to the occurrence of surface related traps, which was confirmed by the observation of kink and hysteresis effect on dc and ac IDS–VDS characteristics, respectively. Though the Si3N4 passivated HEMTs show better dc characteristics, the breakdown voltage (BVgd) characteristics are not comparable with SiO2, SiON passivated and unpassivated HEMTs. The SiON is also a very promising candidate as a surface passivant for AlGaN/GaN HEMTs because it shows better BVgd with low hysteresis width and small ID collapse than Si3N4 passivated HEMTs.

Spectroscopic ellipsometry (SE) together with the optical transmission method is successfully used to determine the refractive index n and absorption coefficient α of undoped gallium nitride film over the spectral range of 0.78–4.77 eV of photon energy. The SE measurement is carried out at angle of incidence of 60° over the 1.5–4.77 eV energy range and optical transmission measurement over the 0.78–3.55 eV energy range. The refractive index n and absorption coefficient α obtained by both methods show unique results in the overlap wavelength region. Refractive index n is found to follow the Sellmeir dispersion relationship n2(λ)=2.272+304.72/(λ2−294.02) below the fundamental band edge. A free excitonic structure at the band is clearly observed at room temperature, with the transmission energy of free exciton at 3.44 eV, which is in reasonable agreement with the reported results.

No abstract

A single crystal GaN thin film was successfully grown on a Si (111) substrate by means of atmospheric pressure metalorganic chemical vapor deposition. Though there is a large difference in thermal expansion coefficients between GaN and Si, an intermediate layer consisting of AlN and AlGaN improved the quality of GaN on Si and reduced meltback etching during growth. Pits and cracks were not observed on the substrate and a mirror-like surface was obtained. The full-width at half maximum (FWHM) of the double-crystal X-ray rocking curve for GaN(0004) was 600 arcsec. Photoluminescence measurement at room temperature for a Si-doped film revealed a sharp band-edge emission with a FWHM of 62.5 meV, which is the narrowest value reported to date.