The Current Aperture Vertical Electron Transistor (CAVET) combines the high conductivity of the two dimensional electron gas channel at the AlGaN/GaN heterojunction with better field distribution offered by a vertical design. In this work, CAVETs with buried, conductive p-GaN layers as the current blocking layer are reported. The p-GaN layer was regrown by metalorganic chemical vapor deposition and the subsequent channel regrowth was done by ammonia molecular beam epitaxy to maintain the p-GaN conductivity. Transistors with high ON current (10.9 kA/cm2) and low ON-resistance (0.4 mΩ cm2) are demonstrated. Non-planar selective area regrowth is identified as the limiting factor to transistor breakdown, using planar and non-planar n/p/n structures. Planar n/p/n structures recorded an estimated electric field of 3.1 MV/cm, while non-planar structures showed a much lower breakdown voltage. Lowering the p-GaN regrowth temperature improved breakdown in the non-planar n/p/n structure. Combining high breakdown voltage with high current will enable GaN vertical transistors with high power densities.
The in-situ metalorganic chemical vapor deposition of Al2O3 on Ga-face GaN metal-oxide-semiconductor capacitors (MOSCAPs) is reported. Al2O3 is grown using trimethylaluminum and O2 in the same reactor as GaN without breaking the vacuum. The in-situ MOSCAPs are subjected to a series of capacitance-voltage measurements combined with stress and ultraviolet-assisted techniques, and the results are discussed based on the presence of near-interface states with relatively fast and slow electron emission characteristics. The in-situ MOSCAPs with Al2O3 grown at 900 and 1000 °C exhibit very small hystereses and charge trappings as well as average near-interface state densities on the order of 1012 cm−2eV−1.
Enhancement-mode m-plane AlGaN/GaN heterojunction field-effect transistors were fabricated with an Al2O3 gate dielectric deposited by atomic layer deposition (ALD). A threshold voltage of +3 V and an on/off ratio of 4×106 were obtained, demonstrating excellent subthreshold region characteristics. These results were achieved using non-polar m-plane GaN, Al2O3 as a gate dielectric, and a recessed-gate structure. The devices exhibited 138 mA/mm of maximum drain–source current at a gate–source voltage (Vgs) of +7 V and 45 mS/mm of maximum transconductance at Vgs=+5 V. The interface state density (Dit) of Al2O3 and m-plane GaN was measured using the photo assisted capacitance–voltage method, showing a Dit of (1–2)×1012 cm-2 eV-1. These results indicate the potential of Al2O3 deposited by ALD on m-plane GaN for power switching devices.
Articles you may be interested inNitride passivation reduces interfacial traps in atomic-layer-deposited Al2O3/GaAs (001) metal-oxidesemiconductor capacitors using atmospheric metal-organic chemical vapor deposition Appl. Phys. Lett. 105, 033513 (2014); 10.1063/1.4891431 In-situ metalorganic chemical vapor deposition and capacitance-voltage characterizations of Al2O3 on Ga-face GaN metal-oxide-semiconductor capacitors Appl. Phys. Lett. 103, 053509 (2013); 10.1063/1.4817385Bulk and interface trapping in the gate dielectric of GaN based metal-oxide-semiconductor high-electron-mobility transistors Appl.Two-dimensional electron gases in Ga-face and N-face AlGaN/GaN heterostructures grown by plasma-induced molecular beam epitaxy and metalorganic chemical vapor deposition on sapphireIn situ Al 2 O 3 on Ga-face GaN metal-oxide-semiconductor capacitors (MOSCAPs) were grown by metalorganic chemical vapor deposition and measured using capacitance-voltage techniques. The flat band voltage and hysteresis had a linear relationship with Al 2 O 3 thickness, which indicates the presence of fixed charge and trap states that are located at or near the Al 2 O 3 /GaN interface. In addition, slow and fast near-interface states are distinguished according to their different electron emission characteristics. Atom probe tomography was used to characterize the in situ MOSCAPs to provide information on the Al/O stoichiometric ratios, Al 2 O 3 /GaN interface abruptnesses, and C concentrations. The in situ MOSCAPs with Al 2 O 3 deposited at 700 C exhibited an order of magnitude higher fast near-interface states density but a lower slow near-interface states density compared with those with Al 2 O 3 deposited at 900 and 1000 C. Furthermore, the 700 C MOSCAPs exhibited a net negative fixed near-interface charge, whereas the 900 and 1000 C MOSCAPs exhibited net positive fixed near-interface charges. The possible origins of various fixed charge and trap states are discussed in accordance with the experimental data and recently reported first-principals calculations. V C 2013 AIP Publishing LLC. [http://dx.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.