Search

The degradation of transient OFF-state leakage current in AlGaN/GaN HEMTs induced by ON-state gate overdrive was observed and studied. The OFF-state leakage current increases significantly with a pre- ON-state gate overdrive. It takes more than 30 s for the leakage current decay to its equilibrium level in dark. The decay processes follow a stretched-exponential law. We propose that this degradation corresponds to the persistent photoconductivity of GaN buffer induced by the electroluminescence during the Schottky gate overdrive. Both the ON-state gate overdrive bias and duration dependences of the OFF-states leakage degradation were studied. This work indicates that gate-protection is necessary to preserve low OFF-state leakage current and improve device reliability. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

GaN smart power chip technology has been realized using a GaN-on-Si HEMT platform, featuring monolithically integrated high-voltage power devices and low-voltage peripheral devices for mixed-signal functional blocks. In particular, this brief presents the imperative analog functional block-voltage reference generator for smart power applications with wide-temperature-range stability. The circuit is capable of proper functions within a wide temperature range from room temperature up to 250 °C, illustrating the unique advantage of the wide-bandgap GaN in high-temperature operation. The voltage reference generator was designed with an AlGaN/GaN HEMT and Schottky diodes, and the devices were operated in the subthreshold regime to obtain low power consumption. The voltage reference generator achieved an average drift of less than 0.5 mV/°C and can be used as a reference voltage in various biasing and sensing circuits. [ABSTRACT FROM AUTHOR]

The Schottky-source forward current–voltage characteristics were measured and analyzed in a recently reported AlGaN/GaN metal–2-D-electron-gas tunnel junction field-effect transistor (FET) (TJ-FET) in order to characterize the effective Schottky barrier height (SBH) and its gate bias dependence. The SBHs were extracted and found to be gate bias dependent, varying from 0.57 eV at VGS = - \0.5\ \V to 0.3 eV at VGS = \1\ \V. This gate-induced Schottky barrier lowering (SBL) effect is explained by the image-charge effect. A 2-D device simulation is carried out to analyze the SBL effect and is shown to be in good agreement with the experiment results. The larger SBH at lower gate voltage enables off -state blocking, while the lower SBH at higher gate voltage leads to high on -state current driving capability in the AlGaN/GaN TJ-FETs. [ABSTRACT FROM PUBLISHER]

We present the first AlGaN/GaN tunnel-junction FETs (TJ-FETs) featuring a metal–2-D-electron-gas (2DEG) Schottky tunnel junction at the source. The control of the source-to-drain current flow is realized through a gate-controlled tunnel junction instead of a gate-controlled 2DEG channel. The TJ-FETs exhibit normally off operation (Vth = +\1.35\ \V) in an otherwise normally on as-grown sample. The unique high-density 2DEG in AlGaN/GaN heterostructures enables the formation of a Schottky tunnel barrier with nanometer-scale barrier thickness even with a large Schottky barrier height (e.g., \sim0.8 eV). In the off state, the source Schottky junction provides natural reverse-blocking capability, resulting in significant leakage reduction and low off-state current. A drive current of 326 mA/mm, a high ION/IOFF ratio (\10^10), and a low subthreshold swing (89 mV/dec) are obtained. [ABSTRACT FROM PUBLISHER]

A high-performance bootstrapped comparator operating with a single-polarity power supply is demonstrated for GaN high-temperature electronics applications. The comparator features monolithically integrated enhancement-mode (E-mode) and depletion-mode (D-mode) AlGaN/GaN HEMTs. The tail current source uses an E-mode HEMT, enabling single-polarity power supply. The E-mode input stage could cover a wide voltage comparison range (from 1 to 6 V) while the bootstrapped loads are implemented with D-mode HEMTs. At room temperature, the comparator delivers a voltage gain as high as 79 V/V and a unity-gain bandwidth of 206 MHz. At 250 ^ \circ\C, a maximum voltage gain of 40 V/V and a unity-gain bandwidth of 84 MHz are obtained. [ABSTRACT FROM AUTHOR]