In this work, a δ-doped p-GaN/u-GaN/AlGaN multi-channel heterostructure is proposed and fabricated by metal-organic chemical vapor deposition (MOCVD). Hall measurement results indicate that the optimized multi-channel structure achieves a record-low sheet resistance of 7529 Ω/□ by MOCVD. The AlGaN/GaN/AlGaN sandwich structure strengthens the quantum confinement for holes and leads to a high polarization-induced hole density of 8.80 × 1013 cm−2. By spatially segregating charge carriers across multiple channels, the multi-channel architecture mitigates inter-carrier scattering and achieves a carrier mobility of 9.42 cm2/V·s. Besides, employing an InGaN layer as the ohmic contact layer significantly reduces the sheet resistance. This achievement provides an important material foundation for the development of high-performance GaN-based p-channel field-effect transistors.

this work, we investigate a buffer-free gallium nitride high electron mobility transistor (GaN HEMT) featuring an ultra-thin AlN back barrier and GaN channel structure. It effectively suppresses defect activation, significantly reducing the trapping/de-trapping of the twodimensional electron gas (2DEG). The device demonstrates excellent characteristics in suppressing drain lag and quiescent drain current (IDQ) drift performances. Pulse measurements reveal that under 20 V drain bias, drain lag decreases from 48.8% to 12.5%, while under RF stress, IDQ drift reduces from 64.03% to 14.1%, with 90% recovery time shortened from 470 -s to 15 -s. This work provides an effective solution at the material-structure level for enhancing the RF amplification stability and reliability of GaN HEMTs.

In this Letter, we present enhancement-mode (E-mode) GaN/AlGaN p-channel metal-oxide-semiconductor field effect transistors (MOSFETs) with excellent performance by introduction of polarization induced tunnel junctions to enhance the source/drain (S/D) contacts and lateral current spreading in the access regions. The S/D contact resistance (RC) of 19.84 Ω·mm at voltage of 5 V was obtained. The fabricated GaN p-MOSFET has a threshold voltage (VTH) of −0.86 V, a high drain current (ID) up to 115 mA/mm, a low on-resistance (Ron) of 52.6 Ω·mm, and an on/off current ratio (ION/IOFF) of 7.2 × 104. The monolithically fabricated GaN power high electron mobility transistor shows a breakdown voltage (BV) more than 1700 V. The proposed technology of GaN p-MOSFETs was promising in the applications of GaN logic and drivers for all-GaN monolithic power integrated circuits.

In this Letter, we present a p-GaN gate enhancement-mode GaN-on-Si high-electron mobility transistor fabricated using Mg-acceptor re-passivation realized through ammonia plasma treatment. The gate-to-source and gate-to-drain access regions of the device were treated with ammonia plasma using a plasma-enhanced chemical vapor deposition system, resulting in the formation of a high-resistivity GaN cap layer. The fabricated device has a high threshold voltage (VTH) of 2.0 V and a low gate reverse leakage current (IGR) of 10-11 A/mm. A breakdown voltage (BVOFF) of 670 V together with a specific on-resistance (R-on,R-sp) of 0.87 m Omega cm(2) was obtained in a device with LGD = 6 mu m. The measured dynamic on-resistance (R-on,R-d) at a quiescent drain voltage (V-ds,V-q) of 600 V with a stress time of 10 and 120 s is 1.06 and 1.34 times of the static on-resistance (R-on,R-s), respectively. Good thermal stability of V-TH and gate current I-G were observed after a thermal stress at 175 degrees C for 100 h. The developed fabrication techniques exhibit a great potential to be applied into GaN power transistors.

As the third generation semiconductor material, gallium nitride (GaN) is widely used in electronic devices and optoelectronic devices due to its excellent characteristics such as wide band gap, high breakdown field strength, high electron mobility, outstanding thermal conductivity, and direct band gap. However, it is difficult to obtain high quality single crystal GaN thin films due to the mismatch between GaN material and substrate in early phase of preparation. Until the two-step growth method is proposed, in which the nucleation layer of aluminum nitride (AlN) is firstly grown on the substrate at low temperature, and then GaN is grown at high temperature, the quality of GaN is greatly improved. Nowadays, AlN nucleation layers are fabricated via magnetron sputtering and molecular beam epitaxy, etc. To further improve the quality of GaN crystals, this study used plasma-enhanced atomic layer deposition (PEALD) method to prepare AlN nucleation layers for the epitaxial growth of GaN on a two-inch c-plane sapphire substrate. Compared with the magnetron sputtering method and molecular beam epitaxy method, the crystal quality of AlN prepared by PEALD method displays advantages of simple process, low cost and high yield. Measurements on deposited AlN films show that the deposition rate is 0.1 nm/cycle and the films have island-like structures varying with its thickness. Epitaxial GaN measurements show that GaN epitaxial layer can obtain the smoothest surface with a root mean square roughness of 0.272 nm, the best optical properties, and the lowest dislocation density when AlN is deposited with a thickness of 20.8 nm. In conclusion, a new method of epitaxial single crystal GaN on AlN prepared by PEALD has been built with optimal deposition at 20.8 nm of AlN to obtain high quality GaN thin films, it can be used to prepare high electron mobility transistors and light-emitting diodes.

In this work, the source of the radio frequency loss in GaN-on-Si materials is investigated in detail. Through measuring S parameters and capacitor voltage characters of samples with different reactive ion etching depths, it is revealed that the radio frequency loss derives from the p-type parasitic channel at the Si interface induced by the diffusion aluminum atom. Based on this viewpoint, the donor phosphorus compensation method was proposed to compensate the p-type parasitic channel of the diffusion Al atom. The approximately linear distribution state of the in situ aluminum diffusion and the normal distribution state ex situ phosphorus ion implantation is revealed according to secondary ion mass spectroscopy and transport of ions in matter (TRIM) simulation methods. Moreover, the variable power phosphorus ion implantation is employed to finely compensate the parasitic channel. As a result, an ultralow coplanar waveguide RF loss of 0.4 dB/mm at 40 GHz is obtained with 600 nm metal thickness. The results in this work have an instructive significance for the application of GaN-on-Si in the future.

We report normally off AlGaN/GaN high‐electron mobility transistors realized by using the thin and high Al composition barrier design in conjunction with O 2 plasma implantation. The AlGaN barrier layer under the gate is selectively treated by low‐energy O 2 plasma in order to positively shift the threshold voltage of devices. The obtained enhancement‐mode HEMT exhibits a threshold voltage ( V TH ) of +1 V, a high peak transconductance of ∼230 mS mm −1 , and a maximum drain current of 424 mA mm −1 at a gate bias of 3 V for a gate length of 0.6 µm. A suppressed gate reverse leakage current and a high breakdown voltage of 450 V are achieved. Moreover, gradually partial oxidation of AlGaN barrier layer is determined to be responsible for the plasma‐induced V TH modulation effect through a systematic investigation. The results indicate O 2 plasma implantation can be a promising method for fabrication of enhancement‐mode GaN‐based devices.

Nonpolar（11ˉ20） GaN films are grown on the etched a-plane GaN substrates via metalorganic vapor phase epitaxy.High-resolution X-ray diffraction analysis shows great decreases in the full width at half maximum of the samples grown on etched substrates compared with those of the sample without etching, both on-axis and off-axis, indicating the reduced dislocation densities and improved crystalline quality of these samples. The spatial mapping of the E2（high） phonon mode demonstrates the smaller line width with a black background in the wing region, which testifies the reduced dislocation densities and enhanced crystalline quality of the epitaxial lateral overgrowth areas. Raman scattering spectra of the E2（high） peaks exhibit in-plane compressive stress for all the overgrowth samples, and the E2（high） peaks of samples grown on etched substrates shift toward the lower frequency range, indicating the relaxations of in-plane stress in these GaN films.Furthermore, room temperature photoluminescence measurement demonstrates a significant decrease in the yellow-band emission intensity of a-plane GaN grown on etched templates, which also illustrates the better optical properties of these samples.

A non-recessed-gate quasi-E-mode double heterojunction AlGaN/GaN high electron mobility transistor (quasi-E-DHEMT) with a thin barrier, high breakdown voltage and good performance of drain induced barrier lowering (DIBL) was presented. Due to the metal organic chemical vapor deposition (MOCVD) grown 9-nm undoped AlGaN barrier, the effect that the gate metal depleted the two-dimensiomal electron gas (2DEG) was greatly impressed. Therefore, the density of carriers in the channel was nearly zero. Hence, the threshold voltage was above 0 V. Quasi-E-DHEMT with 4.1-μm source-to-drain distance, 2.6-μm gate-to-drain distance, and 0.5-μm gate length showed a drain current of 260 mA/mm. The threshold voltage of this device was 0.165 V when the drain voltage was 10 V and the DIBL was 5.26 mV/V. The quasi-E-DHEMT drain leakage current at a drain voltage of 146 V and a gate voltage of −6 V was below 1 mA/mm. This indicated that the hard breakdown voltage was more than 146 V.

We have investigated the influence of growth temperature on N-polar GaN epitaxial layers deposited on sapphire substrates by metal-organic chemical vapor deposition (MOCVD). The GaN films were grown at various temperatures (1050 °C, 1000 °C, 950 °C, 900 °C). The sheet resistivity of the GaN film was 2153 ohm/□ at 950 °C, which is 6 times higher than that at 1050 °C (361 ohm/□). Secondary ion mass spectroscopy (SIMS) measurement confirmed that the increase of carbon impurity concentration was responsible for the above phenomena. High-resolution X-ray diffraction (HRXRD), photoluminescence (PL) and Raman measurements showed that the GaN film quality did not deteriorate seriously at low growth temperature, implying that reducing the growth temperature would be a feasible method to obtain highly insulating N-polar GaN films. However, further reducing the growth temperature to 900 °C led to the sharp increase of oxygen impurity concentration and the decrease of sheet resistivity. This mechanism is explained in detail.