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We report the modification and control of threshold voltage in enhancement and depletion mode AlGaN/GaN metal-insulator-semiconductor heterostructure field effect transistors through the use of in-situ fluorine doping of atomic layer deposition Al2O3. Uniform distribution of F ions throughout the oxide thickness are achievable, with a doping level of up to 5.5 × 1019 cm-3 as quantified by secondary ion mass spectrometry. This fluorine doping level reduces capacitive hysteretic effects when exploited in GaN metal-oxide-semiconductor capacitors. The fluorine doping and forming gas anneal also induces an average positive threshold voltage shift of between 0.75 and 1.36V in both enhancement mode and depletion mode GaN-based transistors compared with the undoped gate oxide via a reduction of positive fixed charge in the gate oxide from +4.67 × 1012 cm-2 to -6.60 × 1012 cm-2. The application of this process in GaN based power transistors advances the realisation of normally off, high power, high speed devices. [ABSTRACT FROM AUTHOR]

This letter reports a simple approach to significantly improve the performance of 340 nm ultraviolet light emitting diodes (UV-LEDs) on an AlN buffer layer. Greatly improved optical and electrical properties of the 340 nm UV-LED have been achieved by using a very thin GaN interlayer (10–20 nm), deposited on AlN as a buffer layer directly on sapphire prior to growth of the UV-LED structure. Compared with the UV-LED without the thin GaN interlayer, the output power of the LED with it is increased by a factor of ∼2.2, and the applied bias voltage at 20 mA drops from 6.5 to ∼5 V. High resolution transmission electron observation indicates that the thin GaN interlayer can effectively stop the penetration of the dislocations in the AlN buffer layer into the overlaying AlGaN layer, while most of the dislocations in the AlN buffer layer in the UV-LED without the thin GaN interlayer can propagate into the overlying AlGaN layer. Therefore, the enhanced performance of the 340 nm UV-LEDs results from a massive reduction in dislocation density in the overlying device structure due to the very thin GaN interlayer. Since it is extremely difficult to reduce the dislocation density in an AlN layer on sapphire, the simple and reliable approach reported in this letter provides a good alternative option to prevent the propagation of dislocations from an AlN buffer into an overlying device structure. [ABSTRACT FROM AUTHOR]

Determines the roles of first atomic layers in the growth of SrTiO[sub 3] films on LaAlO[sub 3] substrates. Transition from layer-by-layer growth to island growth seen in the electrically compensated initial layer in the LaO-terminated substrate; Defects in the noncompensated initial layer in the AlO[sub 2]-terminated substrate.