Inductively coupled plasma (ICP) etch rates for GaN are reported as a function of plasma pressure, plasma chemistry, rf power, and ICP power. Using a Cl2/H2/Ar plasma chemistry, GaN etch rates as high as 6875 Å/min are reported. The GaN surface morphology remains smooth over a wide range of plasma conditions as quantified using atomic force microscopy. Several etch conditions yield highly anisotropic profiles with smooth sidewalls. These results have direct application to the fabrication of group-III nitride etched laser facets.

The competition between band gap and the 2.2 eV ͑yellow͒ luminescence of epitaxial GaN is studied for excitation densities ranging from 5ϫ10 Ϫ6 to 50 W/cm 2. The ratio of the peak intensities of the band gap-to-yellow luminescence changes from 4:1 to 3000:1 as the excitation density is increased by 7 orders of magnitude. At room temperature, the band gap luminescence linewidth is 2.3kT, close to the theoretical minimum of 1.8kT. A model is developed describing the intensity of the two radiative transitions as a function of the excitation density. This model is based on bimolecular rate equations and takes into account shallow impurities, deep levels, and continuum states. The theoretically predicted dependences of the two different luminescence channels follow power laws with exponents of 1 2 , 1 and 3 2. Thus the intensity of the yellow luminescence does not saturate at high excitation densities. These dependences are in excellent agreement with experimental results. The relevance of the results for optoelectronic GaN devices is discussed. It is shown that the peak intensity of the yellow luminescence line is negligibly small at typical injection currents of light-emitting diodes and lasers.

Ga 2 O 3 (Gd 2 O 3 ) was deposited on GaN for use as a gate dielectric in order to fabricate a depletion metal–oxide–semiconductor field-effect transistor (MOSFET). Analysis of the effect of temperature on the device shows that gate leakage is significantly reduced at elevated temperature relative to a conventional metal–semiconductor field-effect transistor fabricated on the same GaN layer. MOSFET device operation in fact improved upon heating to 400 °C. Modeling of the effect of temperature on contact resistance suggests that the improvement is due to a reduction in the parasitic resistances present in the device.

A femtosecond optically detected time-of-flight technique that monitors the change in the electroabsorption associated with the transport of photogenerated carriers in a GaN p–i–n diode has been used to determine the room-temperature electron transit time and steady-state velocity as a function of electric field. The peak electron velocity of 1.9×107 cm/s, corresponding to a transit time of 2.5 ps, is attained at 225 kV/cm. The shape of the velocity-field characteristic is in qualitative agreement with theoretical predictions.

Negative differential resistance associated with hot phonons J. Appl. Phys. 112, 063707 (2012) Photoluminescence properties and high resolution x-ray diffraction investigation of BInGaAs/GaAs grown by the metalorganic vapour phase epitaxy method J. Appl. Phys. 112, 063109 (2012) Optical properties of InGaPN epilayer with low nitrogen content grown by molecular beam epitaxy J. Appl. Phys. 112, 063507 (2012) Residual compressive stress induced infrared-absorption frequency shift of hexagonal boron nitride in cubic boron nitride films prepared by plasma-enhanced chemical vapor deposition J. Appl. Phys. 112, 053502 (2012) Spontaneous emission and optical gain characteristics of blue InGaAlN/InGaN quantum well structures with reduced internal fieldWe present the results of optical studies of the properties of In x Ga 1Ϫx N epitaxial layers (0Ͻx Ͻ0.2) grown by metalorganic chemical vapor deposition. The effects of alloying on the fundamental band gap of In x Ga 1Ϫx N were investigated using a variety of spectroscopic techniques. The fundamental band-gap energies of the In x Ga 1Ϫx N alloys were determined using photomodulation spectroscopy measurements and the variation of the fundamental band gap was measured as a function of temperature. The effects of pressure on the band gap for In x Ga 1Ϫx N samples with different alloy concentrations were examined by studying the shift of photoluminescence ͑PL͒ emission lines using the diamond-anvil pressure-cell technique. The results show that PL originates from effective-mass conduction-band states. Anomalous temperature dependence of the PL peak shift and linewidth as well as the Stokes shift between photoreflectance and PL lines is explained by composition fluctuations in as-grown InGaN alloys.