We demonstrate large area (25 000 μm2) Al-rich AlGaN-based avalanche photodiodes (APDs) grown on single crystal AlN substrates operating with differential (the difference in photocurrent and dark current) signal gain of 100 000 at 90 pW (<1 μW cm−2) illumination with very low dark currents <0.1 pA at room temperature under ambient light. The high gain in large area AlGaN APDs is attributed to a high breakdown voltage at 340 V, corresponding to very high breakdown fields ∼9 MV cm−1 as a consequence of low threading and screw dislocation densities < 103 cm−2. The maximum charge collection efficiency of 30% was determined at 255 nm, corresponding to the bandgap of Al0.65Ga0.35N, with a response of 0.06 A/W. No response was detected for λ > 280 nm, establishing solar blindness of the device.

We demonstrate a method for nanowire formation by natural selection during wet anisotropic chemical etching in boiling phosphoric acid. Nanowires of sub-10 nm lateral dimensions and lengths of 700 nm or more are naturally formed during the wet etching due to the convergence of the nearby crystallographic hexagonal etch pits. These nanowires are site controlled when formed in augmentation with dry etching. Temperature and power dependent photoluminescence characterizations confirm excitonic transitions up to room temperature. The exciton confinement is enhanced by using two-dimensional confinement whereby enforcing greater overlap of the electron-hole wave-functions. The surviving nanowires have less defects and a small temperature variation of the output electroluminescent light. We have observed superluminescent behaviour of the light emitting diodes formed on these nanowires. There is no observable efficiency roll off for current densities up to 400 A/cm2.

We have demonstrated an electrically injected ultra-low threshold (8.9 nA) room temperature InGaN/GaN based lateral nanowire laser. The nanowires are triangular in shape and survived naturally after etching using boiling phosphoric acid. A polymethyl methacrylate (PMMA) and air dielectric distributed mirror provide an optical feedback, which together with one-dimensional density of states cause ultra-low threshold lasing. Finite difference eigen-mode (FDE) simulation shows that triangular nanowire cavity supports single dominant mode similar to TE01 that of a corresponding rectangular cavity with a confinement factor of 0.18.

We demonstrate Si-implanted AlN with high conductivity (>1 Ω−1 cm−1) and high carrier concentration (5 × 1018 cm−3). This was enabled by Si implantation into AlN with a low threading dislocation density (TDD) (<103 cm−2), a non-equilibrium damage recovery and dopant activation annealing process, and in situ suppression of self-compensation during the annealing. Low TDD and active suppression of VAl-nSiAl complexes via defect quasi Fermi level control enabled low compensation, while low-temperature, non-equilibrium annealing maintained the desired shallow donor state with an ionization energy of ∼70 meV. The realized n-type conductivity and carrier concentration are over one order of magnitude higher than that reported thus far and present a major technological breakthrough in doping of AlN.

We report a kV class, low ON-resistance, vertical GaN junction barrier Schottky (JBS) diode with selective-area p-regions formed via Mg implantation followed by high-temperature, ultra-high pressure (UHP) post-implantation activation anneal. The JBS has an ideality factor of 1.03, a turn-on voltage of 0.75 V, and a specific differential ON-resistance of 0.6 mΩ·cm2. The breakdown voltage of the JBS diode is 915 V, corresponding to a maximum electric field of 3.3 MV/cm. These results underline that high-performance GaN JBS can be realized using Mg implantation and high-temperature UHP post-activation anneal.

High room temperature n-type mobility, exceeding 300 cm2/Vs, was demonstrated in Si-doped AlN. Dislocations and CN−1 were identified as the main compensators for AlN grown on sapphire and AlN single crystalline substrates, respectively, limiting the lower doping limit and mobility. Once the dislocation density was reduced by the growth on AlN wafers, C-related compensation could be reduced by controlling the process supersaturation and Fermi level during growth. While the growth on sapphire substrates supported only high doping ([Si] > 5 × 1018 cm−3) and low mobility (∼20 cm2/Vs), growth on AlN with proper compensation management enabled controlled doping at two orders of magnitude lower dopant concentrations. This work is of crucial technological importance because it enables the growth of drift layers for AlN-based power devices.

Record low resistivities of 10 and 30 Ω cm and room-temperature free hole concentrations as high as 3 × 1018 cm−3 were achieved in bulk doping of Mg in Al0.6Ga0.4N films grown on AlN single crystalline wafer and sapphire. The highly conductive films exhibited a low ionization energy of 50 meV and impurity band conduction. Both high Mg concentration (>2 × 1019 cm−3) and low compensation were required to achieve impurity band conduction and high p-type conductivity. The formation of VN-related compensators was actively suppressed by chemical potential control during the deposition process. This work overcomes previous limitations in p-type aluminum gallium nitride (p-AlGaN) and offers a technologically viable solution to high p-conductivity in AlGaN and AlN.

We demonstrate controlled Si-doping in the low doping range of 5x1015–2.5x1016 cm-3 with mobility >1000 cm2/Vs in GaN films grown by metalorganic chemical vapor deposition. The carbon-related compensation and mobility collapse were prevented by controlling the electrochemical potential near the growth surface via chemical potential control (CPC) and defect quasi-Fermi level (dQFL) point defect management techniques. While the CPC was targeted to reduce the net CN concentration, the dQFL control was used to reduce the fraction of C atoms with the compensating configuration, i.e., CN -1. The low compensating acceptor concentration was confirmed via temperature-dependent Hall-effect analysis and capacitance-voltage measurements.