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The radio frequency (RF) power and noise temperature dependency of buffer-free layer AlGaN/GaN on the 6 in. SiC substrate high electron mobility transistor were studied. The buffer-free structure has improved 3% characteristics of the current collapse and pulse measurement at a 30 V drain quiescent voltage. Compared with the conventional thick buffer layer (1.5–2 μm) structure design, the buffer-free layer with high structural quality AlN nucleation layers can reduce self-heating and thermal boundary resistance effect when the devices operate at a high DC power. The buffer-free device exhibits lower surface temperatures and higher powers at the same VGS and VDS than the standard device in thermal imaging measurements. In addition, traditional iron- or carbon-doped buffers were avoided in this design; thus, the buffer-induced microwave noise and thermal noise can be improved simultaneously. Without Fe- or C-doped buffer-induced trap behavior, the buffer-free structure improves the device DC characteristics and reduces the current collapse effect from the conventional buffer; thus, the device shows better linearity, noise figure, and RF small-signal characteristics. [ABSTRACT FROM AUTHOR]

In this study, we investigated enhance mode (E-mode) p-GaN/AlGaN/GaN high-electron-mobility transistors (HEMTs) with an Al0.5GaN etch-stop layer. Compared with an AlN etch-stop layer, the Al0.5GaN etch-stop layer not only reduced lattice defects but engendered improved DC performance in the device; this can be attributed to the lattice match between the layer and substrate. The results revealed that the Al0.5GaN etch-stop layer could reduce dislocation by 37.5% and improve device characteristics. Compared with the device with the AlN etch-stop layer, the p-GaN HEMT with the Al0.5GaN etch-stop layer achieved a higher drain current on/off ratio (2.47 × 107), a lower gate leakage current (1.55 × 10−5 A/mm), and a lower on-state resistance (21.65 Ω·mm); moreover, its dynamic RON value was reduced to 1.69 (from 2.26). [ABSTRACT FROM AUTHOR]

In this work, the dual junction-high-electron-mobility-transistor (DJ-HEMT) was investigated. The thin AlGaN was grown between the p-GaN gate and gate metal. In the TCAD simulations, the band gap and electric field were shown in this letter, proving the dual junction forming. Moreover, DJ-HEMT shows the high gate voltage swing due to the dual junction at the gate region of device, which enhance gate performance. By contrast with standard p-GaN HEMT (ST-HEMT), DJ-HEMT shows higher $\text{V}_{\text {TH}}$ of 2V, saturation current of 187mA/mm, $\text{I}_{\text {ON}}/\text{I}_{\text {OFF}}$ ratio of $5.1\times 10^{{8}}$ and gate swing voltage which is higher than 20V. In addition, DJ-HEMT also shows the lower device leakage current and superior life time measurement due to the thicker and higher barrier of AlGaN cap layer. [ABSTRACT FROM AUTHOR]

In this study, an AlGaN/GaN high-electron-mobility transistor (HEMT) was grown through metal organic chemical vapor deposition on a Qromis Substrate Technology (QST). The GaN on the QST device exhibited a superior heat dissipation performance to the GaN on a Si device because of the higher thermal conductivity of the QST substrate. Thermal imaging analysis indicated that the temperature variation of the GaN on the QST device was 4.5 °C and that of the GaN on the Si device was 9.2 °C at a drain-to-source current (IDS) of 300 mA/mm following 50 s of operation. Compared with the GaN HEMT on the Si device, the GaN on the QST device exhibited a lower IDS degradation at high temperatures (17.5% at 400 K). The QST substrate is suitable for employment in different temperature environments because of its high thermal stability. [ABSTRACT FROM AUTHOR]

A metal–insulator–semiconductor p-type GaN gate high-electron-mobility transistor (MIS-HEMT) with an Al2O3/AlN gate insulator layer deposited through atomic layer deposition was investigated. A favorable interface was observed between the selected insulator, atomic layer deposition–grown AlN, and GaN. A conventional p-type enhancement-mode GaN device without an Al2O3/AlN layer, known as a Schottky gate (SG) p-GaN HEMT, was also fabricated for comparison. Because of the presence of the Al2O3/AlN layer, the gate leakage and threshold voltage of the MIS-HEMT improved more than those of the SG-HEMT did. Additionally, a high turn-on voltage was obtained. The MIS-HEMT was shown to be reliable with a long lifetime. Hence, growing a high-quality Al2O3/AlN layer in an HEMT can help realize a high-performance enhancement-mode transistor with high stability, a large gate swing region, and high reliability. [ABSTRACT FROM AUTHOR]

Efficient heat removal through the substrate is required in high-power operation of AlGaN/GaN high-electron-mobility transistors (HEMTs). Thus, a SiC substrate was used due to its popularity. This article reports the electrical characteristics of normally off p-GaN gate AlGaN/GaN high-electron-mobility transistors (HEMTs) on a low-resistivity SiC substrate compared with the traditional Si substrate. The p-GaN HEMTs on the SiC substrate possess several advantages, including electrical characteristics and good qualities of epitaxial crystals, especially on temperature performance. Additionally, the price of the low-resistivity SiC substrate is three times lower than the ordinary SiC substrate. [ABSTRACT FROM AUTHOR]