Unpassivated SiO2/AlInN/AlN/GaN metal–oxide–semiconductor high electron mobility transistors (MOSHEMTs) exhibiting a thin barrier layer are investigated with a particular focus on their dc characteristics dependence on the gate length. The epiwafer exhibits a sheet resistance of ∼250 Ω/□ and a channel charge density of 7.4 × 1012 cm−2 deduced from the 1 MHz capacitance–voltage curves. The results indicate that the thickness of the AlInN barrier can be reduced below 5 nm without degradation of the insulated gate devices performance. For transistors with gate lengths (LG) between 1.8 and 2.0 µm, dc drain saturation currents densities as high as 1.8 A mm−1 are achieved at +4 V gate–source bias (VGS) with very low reverse gate leakage currents. The electron zero-bias drift mobility was determined to be 1670 cm2 V−1 s−1 from the low-field channel conductance measurements. On the other side, using an analytical model it is found that the maximum output current density at VGS = 0 V can be enhanced by ∼23% when LG is scaled from 1.8 µm down to 100 nm. With further improvement of the quality of the gate insulating oxide layer and the implementation of surface passivation, both with the aim of suppressing the observed current collapse, the presented results suggest that these MOSHEMTs could become very attractive for the realization of high-power electronics.

We report on the substrate laser lift-off (LLO) in lateral conduction flip-chip (FC) deep-UV light-emitting diodes (LEDs) with peak emission wavelength at 285 nm. The AlGaN-based LED epilayer structure was grown on a low-defect 2 µm-thick AlN/sapphire template and processed into 3×3 small periphery pixel-LED arrays. The total p-contact area of the 9 pixel, single chip devices was 180 ×180 µm2. Our results show that the use of FC die assembly with epoxy underfilling the gap between the chip and the submount dramatically increase the yield of damage-free debonding of sapphire and the overlying AlN layer. Equally important, no noticeable degradation of the electrical and optical characteristics of the thin-film light emitters was observed following the LLO process.

An attempt has been made to investigate nucleation and growth mechanism of III-V compound semiconductors from vapour-phase epitaxy (VPE) and liquid-phase electroepitaxial (LPEE) growth techniques. Critical nucleation parameters have been derived using classical heterogeneous nucleation theory. The growth rate expressions have been developed in terms of input parameters for VPE and LPEE growth techniques. The model has been employed to understand the growth kinetics of quaternary Ga III the In-Ga- HC1-PHJ-AsHJ-H2 system during VPE growth and InAs during LPEE growth process. The effect of different experimental input  parameter. on the nucleation and growth behaviour have been studied in detail.

We report on the improved light extraction efficiency of 287 nm small periphery AlGaN/AlGaN thin-film flip-chip (TFFC) light-emitting diodes (LEDs) fabricated using the laser lift-off technique. After sapphire substrate removal, the exposed AlN N-face was etched in a KOH solution. The result was a 1.5-fold increase in the TFFC device output power at 20 mA dc current injection, which was attributed to the AlN surface texturing. TFFC die encapsulation process produced an additional 1.34-fold enhancement of the emitted light power. More importantly, the encapsulated thin-film LEDs exhibited a similar reliability performance compared to encapsulated conventional FC LEDs processed from the same epiwafer, and with no noticeable degradation of the encapsulating material optical properties. (C) 2013 Elsevier Ltd. All rights reserved.

The dc operation of high-quality AlGaN/GaN metal–oxide–semiconductor high-electron-mobility transistors (MOSHEMTs) on Si (111) substrates, fabricated using $\hbox{SiO}_{2}$ as the gate insulator, is investigated for the first time as a function of ambient temperature $(T)$. $I$ –$V$ and $C$ –$V$ characteristics of these depletion-mode devices are studied in the temperature range of 25–200 $^{\circ}\hbox{C}$ , and the results are compared to those of reference AlGaN/GaN HEMTs processed on the same wafer and of identical geometry. For devices with an 8-$\mu\hbox{m}$ drain-to-source separation and $\hbox{1} \times \hbox{2.5} \times \hbox{100}\ \mu \hbox{m}^{2}$ gate dimensions, the maximum output current density was about 730 mA/mm at $+$2 V gate bias for both types of transistors. The thermal behavior of the MOSHEMTs on Si was found to resemble that of devices grown on sapphire and silicon carbide with the gate leakage current exhibiting a rapid increase with $T$ but remaining below the levels seen in the reference HEMTs. The maximum drain current also showed a relatively smaller degradation at elevated temperatures as compared to previously published data.

The dc operation of high-quality AlGaN/GaN metal-oxide-semiconductor high-electron-mobility transistors (MOSHEMTs) on Si (111) substrates, fabricated using SiO2 as the gate insulator, is investigated for the first time as a function of ambient temperature (T). I-V and C-V characteristics of these depletion-mode devices are studied in the temperature range of 25-200 degrees C, and the results are compared to those of reference AlGaN/GaN HEMTs processed on the same wafer and of identical geometry. For devices with an 8-mu m drain-to-source separation and 1 x 2.5 x 100 mu m(2) gate dimensions, the maximum output current density was about 730 mA/mm at + 2 V gate bias for both types of transistors. The thermal behavior of the MOSHEMTs on Si was found to resemble that of devices grown on sapphire and silicon carbide with the gate leakage current exhibiting a rapid increase with T but remaining below the levels seen in the reference HEMTs. The maximum drain current also showed a relatively smaller degradation at elevated temperatures as compared to previously published data.

This work reports on the dc performance of AlGaN/GaN metal-oxide-semiconductor high electron mobility transistors (MOSHEMTs) grown on Si (111) substrate and the study of current dispersion in these devices using various widely adopted methods. The MOSHEMTs were fabricated using a very thin (4.2 nm) SiO2 film as the gate insulator and were subsequently passivated with about 30 nm thick Si3N4 layer. For devices with 2.5 mu m long gates and a 4 mu m drain-to-source spacing, the maximum saturation drain current density was 822 mA mm-(1) at + 4 V gate bias and the peak external transconductance was similar to 100 mS mm(-1). Furthermore, the oxide layer successfully suppressed the drain and gate leakage currents with the subthreshold current and the gate diode current levels exceeding by more than three orders of magnitude the levels found in their Schottky gate counterparts. Capacitance-voltage and dynamic current-voltage measurements were carried out to assess the oxide quality as well as the devices' surface properties after passivation. The efficacy of each of these characterization techniques to probe the presence of interface traps and oxide charge in the nitride-based transistors is also discussed.

The dc operation of high-quality AlGaN/GaN metal–oxide–semiconductor high-electron-mobility transistors (MOSHEMTs) on Si (111) substrates, fabricated using $\hbox{SiO}_{2}$ as the gate insulator, is investigated for the first time as a function of ambient temperature $(T)$. $I$ –$V$ and $C$ –$V$ characteristics of these depletion-mode devices are studied in the temperature range of 25–200 $^{\circ}\hbox{C}$ , and the results are compared to those of reference AlGaN/GaN HEMTs processed on the same wafer and of identical geometry. For devices with an 8-$\mu\hbox{m}$ drain-to-source separation and $\hbox{1} \times \hbox{2.5} \times \hbox{100}\ \mu \hbox{m}^{2}$ gate dimensions, the maximum output current density was about 730 mA/mm at $+$2 V gate bias for both types of transistors. The thermal behavior of the MOSHEMTs on Si was found to resemble that of devices grown on sapphire and silicon carbide with the gate leakage current exhibiting a rapid increase with $T$ but remaining below the levels seen in the reference HEMTs. The maximum drain current also showed a relatively smaller degradation at elevated temperatures as compared to previously published data.

We report on observation of stimulated emission at 258 nm in AlN/AlGaN multiple quantum wells. The structures were grown over Al-face single crystal bulk AlN substrates. AlN/AlGaN structures with 50% of Al in the well material were grown using low-pressure metalorganic chemical vapour deposition. Characterization by using X-ray, AFM, SEM, and photoluminescence techniques indicated high structural quality of the structures. The stimulated emission was measured using the variable stripe length method under excitation by 4-ns-long pulses of the fifth harmonic of Nd:YAG laser radiation at 213 nm (5.82 eV). The stimulated emission exhibited a characteristic superlinear dependence of emission intensity on the pump intensity as well as an exponential increase of the sample-edge emission intensity with increasing stripe length up to ∼430 μm and the intensity saturation beyond this range. The observation of stimulated emission at 258 nm is very promising for the future development of III-nitride-based deep-UV laser diodes on bulk AlN substrates.

This letter presents the dc characteristics of normally Off AlInN/AlN/GaN metal-oxide-semiconductor heterostructure field-effect transistors (MOS-HFETs). The devices were fabricated using a recessed gate and SiON dielectric layers for gate isolation. For a device with a 1.5 mu m gate length and an 8-mu m-long channel, the threshold voltage was above +1.5V and a maximum drain current density of 0.7A/mm was reached under 6V gate bias. These enhancement-mode MOS-HFETs have an excellent potential for power electronics applications. (C) 2011 The Japan Society of Applied Physics

The growth of semipolar AlN and AlGaN epilayers on m-plane sapphire substrates by metalorganic chemical vapor deposition (MOCVD) has been investigated for the first time. The implementation of pulsed MOCVD technique for the deposition of the AlN buffer, and the insertion of a strain relieving AlN/AlGaN short-period superlattice structure proved instrumental in the growth of a thick, crack-free, and single domain n-Al0.56Ga0.44N ($11{\bar {2}}2$) films, which also exhibit a good crystal quality. To assess the suitability of this AlGaN/AlN/m-sapphire template for practical use in deep-ultraviolet light emitters, both polar (0001) and semipolar ($11{\bar {2}}2$) AlGaN multiple quantum wells (MQWs) were grown side-by-side. The room temperature photoluminescence (PL) spectra of the semipolar MQW structure peaked at 305?nm, which was approximately 10?nm longer than the PL peak originating from the reference polar MQWs. Besides, the semipolar MQWs showed a fairly excitation-independent emission wavelength, which suggests the absence of any polarization-induced electric fields. The intensity of the luminescence from the c-oriented MQWs was, however, stronger than that of its semipolar counterpart. The result indicates that further reduction of the extended defects density in ($11{\bar {2}}2$) AlGaN is critical to significantly improving the optical properties of the overlying quantum heterostructures, and potentially achieving efficient optoelectronic devices.