The recombination rates are measured and analyzed for red-emitting InGaN light-emitting diodes (LEDs) to better understand the factors that limit their efficiency. InGaN/AlGaN/GaN multiple quantum well (MQWs) are grown with $\text{x}\ge 0.28$ in the InxGa $_{\mathrm {1-x}}\text{N}$ quantum well. The AlyGa $_{\mathrm {1-y}}\text{N}$ interlayers (ILs) with high Al-content ( $\text{y}>$ 0.8) are employed because they result in smoother surfaces with smaller V-pits and higher photoluminescence efficiency. The IL-MQWs are formed on GaN and InzGa $_{\mathrm {1-z}}\text{N}$ /GaN superlattice (SL) underlayers (ULs) with $z =0.015$ , 0.025, and 0.065. Differences in $B$ coefficients (radiative recombination) within this set result from changes in wavefunction overlap caused by differences in layer thickness and composition in the IL-MQW. IL-MQWs grown on SL-ULs have $A$ coefficients (Shockley-Reed-Hall recombination) that are lower than expected, indicating that the SL-ULs help reduce defect formation. Compared to shorter wavelength InGaN-based LEDs, the $B$ coefficients are $\sim $ 100 times lower due to lower wavefunction overlap. A and $C$ coefficients are higher because of a higher number of defects.

Light-triggered, AlInN/GaN high-electron-mobility transistors (HEMTs) are presented. Selective thermal oxidation of the AlInN barrier between the source and drain depletes the AlInN/GaN 2-dimensional electron gas, enabling enhancement mode operation and light-triggering capability. A commercially available 375 nm laser diode is focused on the bare (no metal) oxidized gate, and despite being below bandgap, it triggers the HEMT into the on-state. The HEMTs have a peak saturation current of ~60 mA/mm, switch at 100 kHz, exhibit sub-microsecond switching times faster than other GaN-based switching devices, and are limited by the laser power supply.

The thermal oxidation rates of Al_0.83In_0.17N layers grown lattice-matched to GaN and the oxide's optical constants are studied. The ∼230 nm thick AlInN layers are placed into a horizontal furnace at elevated temperatures and exposed to either O₂ (dry) or H₂O vapor with an N₂ carrier gas (wet). The samples are oxidized at different temperatures (830–870 °C) and at a constant time or at various times at a constant temperature of 830 °C. Spectroscopic ellipsometry is used to determine the oxide thicknesses, refractive index, and extinction coefficients. The oxidation rate for the wet conditions is faster than for the dry conditions, and both increase with temperature, as expected. However, the oxidation rate is also dynamic with time and can be fitted with the Deal–Grove model, suggesting reaction rate and diffusion-limited processes like other more mature semiconductors. Finally, the dry conditions produce oxides that expand more than the oxides produced under wet conditions. The ability to thermally oxidize Al_0.83In_0.17N layers lattice-matched to GaN is a promising process technique for producing new III-nitride-based electronic devices.

The structure and optical characteristics of thin (∼30 nm) wurtzite AlInN films grown pseudomorphic on free-standing, c-plane GaN substrates are presented. The Al1−xInxN layers are grown by metalorganic chemical vapor deposition, resulting in films with varying In content from x = 0.142 to 0.225. They are measured using atomic force microscopy, x-ray diffraction, reciprocal space mapping, and spectroscopic ellipsometry (SE). The pseudomorphic AlInN layers provide a set where optical properties can be determined without additional variability caused by lattice relaxation, a crucial need for designing devices. They have smooth surfaces (rms < 0.29 nm) with minimum pit areas when the In content is near lattice-matched to GaN. As expected, SE shows that the refractive index increases and the bandgap energy decreases with increased In-content. Plots of bandgap energy vs In content are fitted with a single bowing parameter of 3.19 eV when using bandgap energies for AlN and InN pseudomorphic to GaN, which is lower than previous measurements and closer to theoretical predictions.

Enhancement mode AlInN/gallium nitride (GaN) high-electron-mobility transistors (HEMTs) are fabricated by thermally oxidizing the barrier region under the gate. The oxidation is performed at 850 °C in $\text{O}_{{2}}$ , and a SiNx mask is used to achieve selective oxidization of the AlInN layer. For comparison, a standard Schottky gate and atomic layer deposition (ALD) Al2O3 metal–insulator–semiconductor (MIS) HEMTs are fabricated from the same structure and show depletion mode behavior as expected. Scanning transmission electron microscopy (STEM) and energy-dispersive X-ray spectroscopy (EDS) mappings are performed to characterize the gate of the oxidized HEMTs, showing complete oxidation of the AlInN barrier. All the devices are tested to determine their transfer and output characteristics. The results show that the thermally oxidized gate produces a positive shift in threshold voltage at ~4 V and low currents ( $\sim 2\times 10^{-{7}}$ mA/mm) at zero gate voltage. The oxidized HEMTs are also subjected to postmetallization annealing (PMA) at 400 °C and 500 °C for 10 min flowing 1000 sccm of $\text{N}_{{2}}$ , retaining enhancement mode behavior and leading to a further positive shift in threshold voltage.