We have fabricated and investigated high-voltage GaN vertical Schottky-barrier rectifiers grown by metalorganic chemical vapor deposition. A mesageometry Schottky-barrier rectifier having a 5-μm-thick i region, and processed using reactive-ion etching, exhibited a reverse breakdown voltage of −450 V (at 10 mA/cm2) and an on-resistance of 23 mΩ cm2. For comparison, we have also applied wet chemical etching for the fabrication of mesageometry Schottky-barrier rectifiers. The 2-μm-thick i-region GaN mesa-Schottky rectifiers showed a breakdown voltage of −310 and −280 V for wet-etched and dry-etched devices, respectively, and an on-resistance of 8.2 and 6.4 mΩ cm2, respectively. These results indicate that the performance of the wet-etched rectifiers is comparable to or better than that of comparable dry-etched devices.

We report the growth, fabrication, and characterization of AlxGa1−xN (0⩽x⩽0.60) heteroepitaxial back-illuminated solar-blind p-i-n photodiodes on (0001) sapphire substrates. The group III-nitride heteroepitaxial layers are grown by low-pressure metalorganic chemical vapor deposition on double polished sapphire substrates using various growth conditions. The back-illuminated devices exhibit very low dark current densities. Furthermore, they exhibit external quantum efficiencies up to 35% at the peak of the photoresponse (λ∼280 nm). Improvements were made to the growth technique in order to achieve crack-free Al0.4Ga0.6N active regions on a thick Al0.6Ga0.4N window layer and to obtain activated p-type Al0.4Ga0.6N layers.

The GaN Schottky diodes capable of operating in the 300-700-V range with low turn-on voltage (0.7 V) and forward conduction currents of at least 10 A at 1.4 V (with corresponding forward current density of 500 A/cm 2 ) are attractive for applications ranging from power distribution in electric/hybrid electric vehicles to power management in spacecraft and geothermal, deep-well drilling telemetry.A key requirement is the need for edge-termination design to prevent premature breakdown because of field crowding at the edge of the depletion region. We describe the simulation of structures incorporating various kinds of edge termination, including dielectric overlap and ion-implanted guard rings. Dielectric overlap using 5-µm termination of 0.1-0.2-µm-thick SiO 2 increases the breakdown voltage of quasi-vertical diodes with 3-µm GaN epi thickness by a factor of ϳ2.7. The use of even one p-type guard ring produces about the same benefit as the optimized dielectric overlap termination.

We have studied the low-temperature (4 K) photoluminescence (PL) of a modulation-doped Al0.37Ga0.63N/GaN single heterostructure. Radiative recombination is observed between electrons in the two-dimensional quantum states at the heterointerface and holes in either the flatband region or bound to residual acceptors. This PL emission disappears when the top AlGaN layer is removed by reactive ion etching, indicating that the luminescence is from the two-dimensional electron states. From the peak separation of the luminescence related to the two-dimensional electrons, the maximum electric field at the heterointerface is estimated to be 3.7×104 V/cm.

We report the growth and characterization of InGaN heteroepitaxial thin films and quantum-well heterostructures on (0001) sapphire substrates. The III-N heteroepitaxial layers are grown by metalorganic chemical vapor deposition on sapphire substrates using various growth conditions. A comparison of the 300 K photoluminescence (PL) spectra of the samples indicates that a higher PL intensity is measured for the quantum-well structures having an intentional n-type Si-doping concentration. Furthermore, three-, five-, and eight-period InGaN quantum-well structures exhibit similar narrow PL spectra.