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.

Gallium-nitride-based, blue micro-light-emitting diodes (micro-LEDs) with electro-optical -3 dB modulation bandwidths of 3.73 GHz at 11 kA/cm ² at room temperature and 4.00 GHz at 9 kA/cm ² at 200°C are reported. These bandwidths are the highest reported thus far for micro-LEDs. The micro-LEDs operate at high temperatures, up to 400°C, and bandwidths improve with increased temperatures. The lifetimes and recombination rates of the micro-LEDs active layer are determined by measuring and analyzing the impedance, modulation response, and radiative efficiency. This analysis shows increasing bandwidths with increasing current density and temperature resulting from dominant non-radiative lifetimes.

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.

The recombination rates in an In _0.25 Ga _0.75 N/Al _0.48 Ga _0.52 N/GaN multiple quantum well (MQW) structure are measured to identify the cause of low efficiencies in high In-content InGaN quantum wells. The MQWs emit from 640 to 565 nm and are grown using metal-organic chemical vapor deposition (MOCVD). The addition of AlGaN interlayers within the MQW provides strain balancing and suppresses defect formation in high In-content InGaN quantum wells. The rates are found by transforming the optically measured radiative efficiency, differential carrier lifetimes, and optical absorption. Both components of non-radiative recombination rates, Shockley-Read-Hall (SRH) and Auger recombination, are found to be similar to the values of blue-emitting InGaN MQWs. The low SRH recombination rate is attributed to the use of the AlGaN interlayer. The radiative recombination rate, however, is more than an order of magnitude lower compared to blue emitting (lower In-content) InGaN-based MQWs. While this large reduction in radiative rate can be attributed to differences in carrier overlap and transition energy, it may also include effects of variations in thickness and compositional inhomogeneities.

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.