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We present our latest results on ${L} _{g} = {87}$ nm InAlAs/InGaAs high-electron-mobility transistors with an excellent combination of dc and high-frequency characteristics. We obtained a maximum transconductance of 3 S/mm at ${V}_{\text{DS}} = {0.9}$ V, an ON-resistance of $273~\Omega $ - $\mu \text{m}$ , a current gain cutoff frequency of 559 GHz, and a maximum oscillation frequency of 671 GHz. According to small-signal modeling, these outstanding device metrics are a consequence of the indium-rich InGaAs channel with very high Hall mobility, compact device design with ${L} _ {\text{SD}} = {1}\,\,\mu \text{m}$ , and an optimized gate process that yields well-tempered behavior. [ABSTRACT FROM AUTHOR]

In0.08Al0.92N/GaN fin-type high-electron mobility transistors (fin-HEMTs) with different gate-to-drain lengths (${L} _{\text {gd}}$) are fabricated and characterized by dc and low-frequency noise (LFN) measurements. The fabricated device with the largest ${L} _{\text {gd}}$ exhibits the degradation of the maximum drain current and transconductance with a positive shift of the threshold voltage. LFN measurements of the In0.08Al0.92N/GaN fin-HEMTs reveal clear 1/ ${f}$ behavior of the noise spectra, and the minimum value is observed in the device at ${L} _{\text {gd}} = {20}\,\,\mu \text{m}$. The devices with smaller ${L} _{\text {gd}}$ follow a carrier number fluctuation noise model owing to electron trapping/detrapping into the In0.08Al0.92N barrier layer from the 2-D electron gas (2DEG) channel. In contrast, the device with the largest ${L} _{\text {gd}}$ shows correlated mobility fluctuations due to the large 2DEG mobility fluctuations in the large access area. [ABSTRACT FROM AUTHOR]

Superior device characteristics have been demonstrated with a novel Al(In)N/GaN-based steep fin-type high electron mobility transistor (HEMT) with a fin width ( W\mathrm{ fin} ) of 120 nm, a fin height ( H\mathrm{ fin}) of 250 nm, and a gate length ( LG ) of 200 nm. The proposed device achieved very low drain leakage ( I\mathrm{ off}) < 8 \times 10^{-8} A/mm at 7 V and < 1 \times 10^-6 A/mm at 100 V, which is four orders of improvement over I\mathrm{\scriptscriptstyle OFF} of conventional Al(In)N/GaN HEMTs. In addition, the device exhibits a high ON-state current ( I\mathrm{\scriptscriptstyle ON}) of 1.12 A/mm, a steep sub-threshold swing ( $S$ ) of 63 mV/decade, a low drain-induced barrier lowering of 18.5 mV/V, and a high power-gain cutoff frequency ( f_{T} ) of 21 GHz. [ABSTRACT FROM PUBLISHER]

Normally off Al2O3/GaN MOSFETs are fabricated with a tetramethylammonium hydroxide (TMAH) treatment as a postgate recess etch. The effects of the surface treatment on the etched GaN surface are investigated using low-frequency (1/ f ) noise and capacitance–voltage ( C – V ) measurements. For a quantitative comparison with conventional devices, the oxide trap density ( ) is extracted using the unified 1/ f noise model, whereas the interface trap density ( D\mathbf {it} ) is extracted using the high–low-frequency C – V method. After the TMAH treatment, N_{\mathbf {ot}} is found to have decreased from 5.40 \times 10^{\mathrm {\mathbf {19}}} to 2.50 \times 10^\mathrm \mathbf 19~\mathrmeV^\mathrm \mathbf -1 \mathrmcm^\mathrm \mathbf -3 , whereas D\mathbf {it}^{\vphantom {(}} is decreased from 2.8 \times 10^\mathrm \mathbf 12 to 1.1 \times 10^\mathrm \mathbf 11~\mathrmeV^\mathrm \mathbf -1 \mathrmcm^\mathrm \mathbf -2 , as compared with conventional devices. The surface treatment is thus shown to lower trap density in the Al2O3/GaN MOSFETs by smoothing the surface and suppressing plasma damage in the recessed GaN surfaces. [ABSTRACT FROM AUTHOR]

A single-nanoribbon \Al2\O3\/GaN metal–insulator–semiconductor field-effect transistor (MISFET) has been fabricated. The fabricated device exhibits normally off operation with a threshold voltage of 2.1 V. The device also exhibits superior performances such as a maximum drain current density of 1.51 A/mm, a maximum transconductance of 580 mS/mm, and a field-effect mobility of 293 \cm^2\cdot \V^-1\cdot \s^-1. This is because the electron concentration in the GaN channels can be increased due to the enhanced gate controllability, which, thus, effectively screens the field lines from the interface traps or the defects near the channels to improve the electron mobility in the channel. The nanoribbon \Al2\O3\/GaN MISFET is a very promising candidate for high-performance normally off GaN FETs. [ABSTRACT FROM PUBLISHER]

A \SiO2/\Al2\O3 double dielectric stack layer was deposited on the surface of a GaN-based light-emitting diode (LED). The double dielectric stack layer increases the optical output power of the LED because the first \Al2\O3 layer plays a role as an effective surface passivation layer and the second \SiO2 layer with lower index increases the critical angle of the emitted light and hence the overall extraction efficiency from the LED. The leakage current of the LED passivated with an \Al2\O3 layer was -\3.46 \times \10^-11\ \A at -5 V, at least two and three orders lower in magnitude compared to that passivated with a \SiO2 layer (-\7.14 \times \10^-9\ \A) and that of the nonpassivated LED(-\1.9 \times \10^-8\ \A), respectively, which indicates that the \Al2\O3 layer is very effective in passivating the exposed GaN surface after dry etching and hence reduces the nonradiative recombination as well as reabsorption of the emitted light near the etched surface. [ABSTRACT FROM AUTHOR]

Normally off \Al2\O3\/\GaN MOSFETs are fabricated by utilizing a simple tetramethylammonium hydroxide (TMAH) treatment as a postgate-recess process. The TMAH-treated device with a gate length of 2.5 \mu\m exhibited excellent device performances, such as a threshold voltage of 3.5 V, a maximum drain current of 336 mA/mm, and a breakdown voltage of 725 V, along with extremely small gate leakage current of about \10^-9\ \A/mm at Vgs = \15\ \V, which is approximately six orders lower in magnitude compared to that of the device without TMAH treatment. [ABSTRACT FROM AUTHOR]