Yuji Ando

This paper presents a simple method for accurately calculating quantum mechanical transmission probability and current across arbitrary potential barriers by using the multistep potential approximation. This method is applicable to various potential barriers and wells, including continuous variations of potential energy and electron effective mass. Various potential barrier structures and a hot-electron transistor are analyzed to show the feasibility of this method.

AlGaN-GaN heterojunction field-effect transistors (HFETs) with a field modulating plate (FP) were fabricated on an SiC substrate. The gate-drain breakdown voltage (BV/sub gd/) was significantly improved by employing an FP electrode, and the highest BV/sub gd/ of 160 V was obtained with an FP length (L/sub FP/) of 1 μm. The maximum drain current achieved was 750 mA/mm, together with negligibly small current collapse. A 1-mm-wide FP-FET (L/sub FP/=1 μm) biased at a drain voltage of 65 V demonstrat

An exact model for charge control in two-dimensional field-effect transistors (2DEGFETs) is discussed. The model is based on a first-principles theory, in which self-consistent quantum two-dimensional electron subbands and numerical solutions of Poisson's equation for band bending, space charge, and three-dimensional holes are included. The charge control in InGaAs/AlGaAs pseudomorphic 2DEGFETs is analyzed and compared with that in the GaAs/AlGaAs conventional 2DEGFET. It is shown that a quantum

This paper presents electrical characterization of Al2O3/AlGaN/GaN metal–oxide–semiconductor (MOS) high-electron-mobility transistors (HEMTs) grown on GaN substrates. The postmetallization annealing (PMA) at 300 °C achieved effective reduction of electronic states at the Al2O3/AlGaN interface, leading to improved gate controllability and current linearity of the MOS HEMTs. The MOS HEMT with PMA showed a subthreshold slope of 68 mV dec−1. In addition, excellent operation stability of the MOS HEMT

A practical model for DC, small-signal, and noise characteristics in two-dimensional electron gas field-effect transistors is discussed. The model includes accurate charge-control characteristics based on analytical functions relating carrier concentration to Fermi level. This model allows the influence of drain current, frequency, and device parameters on the noise figure (NF) to be studied. The theory explains the experimentally observed trend in NF behaviors.< <ETX xmlns:mml="http://www.w3.or

SiN-passivated AlGaN/GaN heterojunction FETs (HJFETs) were fabricated on a thinned sapphire substrate. A 16 mm-wide HJFET on a 50 /spl mu/m-thick sapphire exhibited 22.6 W (1.4 W/mm) CW power, 41.9% PAE, and 9.4 dB linear gain at 26 V drain bias. Also, a 32 mm-wide device, measured under pulsed operation, demonstrated 113 W (3.5 W/mm) pulsed power at 40 V drain bias. To our best knowledge, 113 W total power is the highest achieved for GaN on any substrate, establishing the validity of the GaN-on

We have successfully developed a novel AlGaN/GaN FET with dual field-modulating-plates (FPs). The breakdown voltage is enhanced from 125 to 250 V by adding the second FP to the conventional FP structure. Benefiting from the first FP, no current collapse is observed simultaneously. Since the second FP effectively reduces feedback capacitance, this device provides a 3-dB higher gain along with increased linearity and stability. Under a 2.15-GHz W-CDMA modulation scheme, a dual-FP-FET with a 24-mm

This article reports a systematic study on the effects of the epitaxial layer structure on the electrical characteristics of AlGaN/GaN high electron mobility transistors (HEMTs) fabricated on freestanding GaN substrates. First, GaN-on-GaN HEMTs were fabricated comprising channel and buffer layers unintentionally doped with Fe atoms those were diffused from the substrate. Their electrical characteristics were compared with GaN-on-SiC HEMTs. The tradeoff relation between maximum drain current and

A recessed-gate structure was introduced to improve transconductance (gm) and gain characteristics in AlGaN/GaN field-plate (FP) FETs. A maximum gm was improved from 130 to 200 mS/mm by introducing gate recess. Recessed FP-FETs exhibited 3-7 dB higher linear gain as compared with planar FP-FETs. A 1 mm-wide recessed FP-FET biased at a drain voltage of 66 V demonstrated 12.0 W output power, 21.2 dB linear gain, and 48.8 % power added efficiency at 2 GHz. To our knowledge, the power density of 12.

Two-dimensional self-consistent full band Monte Carlo (FBMC) simulator was developed for electron transport in wurtzite phase AlGaN/GaN heterojunction (HJ) FET. Recessed gate Al/sub 0.2/Ga/sub 0.8/N/GaN HJFET structures with an undoped cap layer were simulated, where the spontaneous and piezoelectric polarization effects were taken into account. The polarization effect was shown to not only increase the current density, but also improve the carrier confinement, and hence improve the transconduct

This article reports a systematic study focused on the mechanical stress effect of field-plate dielectric film on the electric characteristics of AlGaN/GaN high-electron mobility transistors (HEMTs). AlGaN/GaN HEMTs were fabricated on SiC substrates, where the stress of a SiN field-plate dielectric film ranged from -252 (compressive) to +26.5 (tensile) MPa. Si-rich and compressive SiN films exhibited a significant increase in the isolation leakage. On the other hand, relatively N-rich and tensil

An accurate two-layer model has been developed for parasitic source resistance in two-dimensional electron gas field-effect transistors (2DEGFETs). In this model, the 2DEG concentration-voltage and current density-voltage relations at the cap/barrier/2DEG junction are taken into account, based on the self-consistent charge control model and effective mass tunneling theory. Empirical 2DEG velocity field characteristics are also included. To show the feasibility of this method, the source resistan