GaN-Based Devices on Si

Properties of InxGa1−xN films in terahertz range Appl. Phys. Lett. 100, 071913 (2012) Thermal carrier emission and nonradiative recombinations in nonpolar (Al,Ga)N/GaN quantum wells grown on bulk GaN J. Appl. Phys. 111, 033517 (2012) Surface depletion mediated control of inter-sub-band absorption in GaAs/AlAs semiconductor quantum well systems Appl. Phys. Lett. 100, 051110 (2012) High-Q optomechanical GaAs nanomembranes Appl. Phys. Lett. 99, 243102 (2011) Mg-induced terahertz transparency of indium nitride films Appl. Phys. Lett. 99, 232117 (2011) Additional information on J. Appl. Phys. GaN films have been deposited by reactive rf sputtering of GaAs target in 100% nitrogen ambient on quartz substrates at different substrate temperatures ranging from room temperature to 700°C. A series of films, from arsenic-rich amorphous to nearly arsenic-free polycrystalline hexagonal GaN, has been obtained. The films have been characterized by phase modulated spectroscopic ellipsometry to obtain the optical parameters, viz., fundamental band gap, refractive index, and extinction coefficient, and to understand their dependence on composition and microstructure. A generalized optical dispersion model has been used to carry out the ellipsometric analysis for amorphous and polycrystalline GaN films and the variation of the optical parameters of the films has been studied as a function of substrate temperature. The refractive index values of polycrystalline films with preferred orientation of crystallites are slightly higher ͑2.2͒ compared to those for amorphous and randomly oriented films. The dominantly amorphous GaN film shows a band gap of 3.47 eV, which decreases to 3.37 eV for the strongly c-axis oriented polycrystalline film due to the reduction in amorphous phase content with increase in substrate temperature.

Section: Introductionmentioning

confidence: 90%

Spectroscopic ellipsometry studies of GaN films deposited by reactive rf sputtering of GaAs target

Biswas

Bhattacharyya

Sahoo

et al. 2008

“…Among the key developments pushed forward today in order to meet these requirements are the usage of large area, low cost Si substrates, non-polar GaN, and an improvement of the chip design. 2 In comparison to conventional thin film LEDs used today, GaN based nanorods (or nanowires) offer many potential advantages. GaN nanorods with high aspect-ratio and large surface-to-volume ratio can dramatically reduce the dislocation density in the upper part of the nanorods.…”

Section: Introductionmentioning

confidence: 99%

GaN based nanorods for solid state lighting

Li¹,

Waag

2012

495

394

In recent years, GaN nanorods are emerging as a very promising novel route toward devices for nano-optoelectronics and nano-photonics. In particular, core-shell light emitting devices are thought to be a breakthrough development in solid state lighting, nanorod based LEDs have many potential advantages as compared to their 2 D thin film counterparts. In this paper, we review the recent developments of GaN nanorod growth, characterization, and related device applications based on GaN nanorods. The initial work on GaN nanorod growth focused on catalyst-assisted and catalyst-free statistical growth. The growth condition and growth mechanisms were extensively investigated and discussed. Doping of GaN nanorods, especially p-doping, was found to significantly influence the morphology of GaN nanorods. The large surface of 3 D GaN nanorods induces new optical and electrical properties, which normally can be neglected in layered structures. Recently, more controlled selective area growth of GaN nanorods was realized using patterned substrates both by metalorganic chemical vapor deposition (MOCVD) and by molecular beam epitaxy (MBE). Advanced structures, for example, photonic crystals and DBRs are meanwhile integrated in GaN nanorod structures. Based on the work of growth and characterization of GaN nanorods, GaN nanoLEDs were reported by several groups with different growth and processing methods. Core/shell nanoLED structures were also demonstrated, which could be potentially useful for future high efficient LED structures. In this paper, we will discuss recent developments in GaN nanorod technology, focusing on the potential advantages, but also discussing problems and open questions, which may impose obstacles during the future development of a GaN nanorod based LED technology.

“…[10][11][12] In view of the wide ranging, potential applications of polycrystalline GaN, sputtering technique has recently become attractive, owing to its versatility and scalability. There have been several early reports on the growth of GaN films by reactive sputtering of Ga target with nitrogen or nitrogen-argon mixture, [13][14][15] though problems of reproducibility arising out of the low melting temperature of gallium have been reported.…”

Section: Introductionmentioning

confidence: 99%

Growth and structure of sputtered gallium nitride films

Yadav¹,

Major²,

Srinivasa³

2007

GaN films have been deposited by radio frequency sputtering of a GaAs target with pure nitrogen. The growth, composition, and structure of the films deposited on quartz substrates have been studied by x-ray diffraction, transmission electron microscopy, and Raman spectroscopy. Films deposited below 300°C are amorphous and As rich. Above 300°C, polycrystalline, hexagonal GaN is formed, along with As rich amorphous phase, which reduces with increasing substrate temperature. At a substrate temperature of 700°C, GaN films, practically free of amorphous phase, and As (<0.5at.%) are formed. The preferred orientation depends strongly on the substrate temperature and is controlled by surface diffusion of adatoms during growth stage. Below 500°C, the surface diffusion between planes dominates and results in the (101¯1) preferred orientation. Above 500°C, the surface diffusion between grains takes over and results in (0002) preferred orientation.