Design and demonstration of EID MOS-HEMTs on Si substrate with normally depleted AlGaN/GaN epitaxial layer

An extrinsic electron induced by a dielectric (EID) AlGaN/GaN MOS high-electron-mobility transistor (HEMT) on Si substrate was designed and investigated. The EID structure with SiO2 deposition and subsequent high-temperature annealing, which induces two-dimensional electron gases (2DEGs) on fully depleted AlGaN/GaN hetero-epitaxial layers with thin AlGaN barrier layer, was applied to access and drift regions in the HEMT. The fabricated HEMT exhibited enhancement-mode operation with a specific on-resistance of 7.6 mΩcm2 and a breakdown voltage of over 1 kV. In addition, electron state analysis using hard X-ray photoelectron spectroscopy revealed that changes in the chemical states of Al and energy level lowering at the SiO2/AlGaN interface affect the induction of 2DEG in the EID structure. The proposed HEMTs should become a strong candidate for highly reliable high-power switching devices due to the damage-less fabrication without dry etching or fluorine plasma exposure processes on the semiconductor layers.

High-Sensitivity Hydrogen Sensor Based on AlGaN/GaN Heterojunction Field-Effect Transistor

We have developed a Pd-functionalized hydrogen gas sensor based on a recessed AlGaN/GaN heterostructure field-effect transistor. The AlGaN barrier layer under the Pd catalyst was partially etched to enhance its sensitivity. Both low-power consumption and high sensitivity were achieved by employing a recessed structure. Sensor characterization was carried out at the temperature range from room temperature to 250 °C, among which the best sensing characteristics were observed at 200 °C. A sensitivity of 380% with a response time of 0.25 s was achieved at a bias voltage of 0.3 V at 200 °C under a hydrogen exposure concentration of 4%. The standby power consumption was only 2 μW for the sensing area of 100×28 μm2 due to the low standby current, which was caused by the recessed AlGaN barrier layer.

The Influence of Anode Trench Geometries on Electrical Properties of AlGaN/GaN Schottky Barrier Diodes

AlGaN/GaN lateral Schottky barrier diodes (SBDs) with three different anode geometries (stripe, circular, and the conventional plane one) and different rows of anode trenches are fabricated and electrically characterized to study the influence of anode trench geometries. The SBDs with anode trenches exhibit the lower on-state resistance (RON) than that with the conventional plane one. It can be explained that the anode trenches made the Schottky metal directly contact to the 2DEG at the sidewall of the AlGaN/GaN interface, removing the AlGaN barrier layer in the conventional plane anode. In addition, the RON of the SBDs with circular trenches is smaller than that of the SBDs with stripe ones. Furthermore, the RON decreases with the increasing rows of anode trenches, which can be attributed to the increased contact area between the Schottky metal and the 2DEG. For the reverse characteristics, the anode trenches do not lead to performance degradation. The fabricated devices exhibit the low reverse current (IR, IR < 1 μA/mm), and the breakdown voltage (VBK) remains unchanged with different anode geometries.

Simulation of Electrical Characteristics on Inhomogeneous Strains in Normally-off HEMTs with p-GaN Gate

Strain is one of the important factors affecting the two-dimensional electron gas (2DEG) transform in AlGaN/GaN material based high electron mobility transistors (HEMTs) by polarization effects. In this paper, the effects of inhomogeneous biaxial strain in different regions of the AlGaN barrier layer on electrical properties of normally-off HEMTs with p-GaN gate were discussed. The results show that biaxial strain applied in three regions has different influence on transfer, output and breakdown characteristics of the device. The strain applied in region under gate has the most significant impact on threshold voltage and drain saturation current with a decreasing of 39% and an increasing of 97% respectively as the strained lattice constant increases from 3.173061Å to 3.187229Å.While, strain applied between gate and drain electrode can improve the off-state breakdown voltage by 12% with the increasing of strained lattice constant.