We report on the study of high-field performance of Si-doped n-AlN layers that were grown using a pulsed metalorganic chemical vapor deposition (PMOCVD) process. In the past we showed this pulsed doping approach to lead to doping efficiency superior to that in the conventional MOCVD process. Here using them as the drift layer for a quasi-vertical conduction Schottky barrier, we show their ability to withstand high reverse bias voltages and sustain an electrical field as high as 9.9 MV cm-1. Our study thus demonstrates the viability of the PMOCVD growth and doping approach to yield n-AlN layers suitable for high current-high voltage devices.

In this paper, we present a study of distribution polarization doped AlxGa1-xN layers and their use in quasi-vertical configuration pn-diodes which exhibited a high breakdown field of 8.5 MV/cm and a large forward current density (~ 23 kA/cm2). We also establish their potential use in UVC light emitters by studying the optical emission from quantum wells inserted at the distribution polarization doped pn-junction interface.

Herein, the first demonstration of hybrid high‐ k oxide (ZrO 2 ‐Al 2 O 3 ) incorporation into extreme bandgap (EBG) Al 0.87 Ga 0.13 N/Al 0.64 Ga 0.36 N metal‐oxide‐semiconductor heterostructure field‐effect transistors (MOSHFETs) is presented, with both planar and recessed‐gate designs on the same AlN/sapphire template with a state‐of‐the‐art low contact resistance of 1.4 Ω mm (contact resistivity, ρ c ≈ 5.7 × 10 −6 Ω cm 2 ). The recessed‐gate MOSHFETs achieve a threshold voltage shift of Δ V TH = 5.8 V, highlighting improved channel control. Static output measurements reveal a peak drain current ( I DS ) of 340 mA mm −1 for the planar gate and 280 mA mm −1 for the recessed gate at V GS = +8 V, with corresponding on–off current ratios of ≈10 6 and ≈10 8 . The recessed‐gate structure demonstrates reduced gate leakage and minimal hysteresis, indicating robust fabrication processes with negligible impact on interface states. Transfer characteristics further show a peak transconductance ( g m ) of 31 and 45 mS mm −1 for the plain and recessed structures, respectively. These findings establish EBG recessed‐gate MOSHFETs as a promising solution for advanced power devices requiring precise threshold voltage control, enhanced on‐state current, and reduced leakage currents.

"Extreme bandgap n-Al0.63Ga0.37N quasi-vertical Schottky barrier diodes (SBDs) with doping densities of approximate to 8 x 1017 cm-3 (Sample A) and approximate to 2 x 1017 cm-3 (Sample B) are grown on an AlN/sapphire substrate using metalorganic-chemical vapor deposition (MOCVD). Sample A achieves a high forward current density of approximate to 59.5 kA cm-2 at 10 V with an ION/IOFF ratio of approximate to 108 (calculated from the forward current at + 3.8 V and the reverse current at -1 V) and an ideality factor of 2.8. Sample B has a forward current density of approximate to 6.25 kA cm-2 and a much better ideality factor of 1.9. For Sample B, a breakdown voltage of 389 V is measured, which translates into a breakdown field of approximate to 7.8 MV cm-1 and a Baliga figure of merit of 630 MW cm-2, which are the highest values ever reported for quasi-vertical Schottky barrier diodes with a similar AlxGa1-xN composition.

Scaling down the GaN channel in a double heterostructure AlGaN/GaN/AlGaN High Electron Mobility Transistor (HEMT) to the thicknesses on the order of or even smaller than the Bohr radius confines electrons in the quantum well even at low sheet carrier densities. In contrast to the conventional designs, this Quantum Channel (QC) confinement is controlled by epilayer design and the polarization field and not by the electron sheet density. As a result, the breakdown field at low sheet carrier densities increases by approximately 36% or even more because the quantization leads to an effective increase in the energy gap. In addition, better confinement increases the electron mobility at low sheet carrier densities by approximately 50%. Another advantage is the possibility of increasing the aluminum molar fraction in the barrier layer because a very thin layer prevents material relaxation and the development of dislocation arrays. This makes the QC especially suitable for high-voltage, high-frequency, high-temperature, and radiation-hard applications.

We report the performance of a bipolar epitaxial graphene (EG)/p-SiC/n+-SiC UV phototransistor fabricated with a Schottky (EG)/SiC junction grown using a SiF4 precursor. The phototransistor showed responsivity as high as 25 A/W at 250 nm in the Schottky emitter (SE) mode. The Schottky collector (SC) mode showed a responsivity of 17 A/W at 270 nm with a visible rejection (270 nm:400 nm)>103. The fastest response was seen in the SC-mode, with 10 ms turn-on and 47 ms turn-off, with a noise equivalent power of 2.3 fW at 20 Hz and a specific detectivity of 4.4 × 1013 Jones. The high responsivity is due to internal gain from bipolar action. We observe additional avalanche gain from the device periphery in the SC-mode by scanning photocurrent microscopy but not in the SE-mode. This high-performance visible-blind photodetector is attractive for advanced applications such as flame detection.

The expected performance of GaN and SiC based power devices far exceeds that of Si power transistors, but the gap between the expected and achieved performance is much larger for GaN transistors. In this paper, we discuss new approaches for shrinking the performance gap for GaN power devices. They include using the quantum well channel designs that lead to the electron wave function penetration into wide band gap cladding layers with the commensurate increase in the breakdown voltage while keeping the advantage of a high mobility in the device channel. The gate edge engineering (beyond just using field plates) optimizes the voltage distribution in the drain-to-gate spacing. It could be combined with a low conducting passivation for smoothing or even eliminating the sharp maximum of the electric field in the vicinity of the gate and field plate edges. Additional contacts in the drain-to-gate spacing for the field control and variable doping implants should allow for further optimization. The perforated channel designs could alleviate both the parasitic series resistance problem and the heat dissipation problem. Extending the gate perforations into the drain-to-gate region allows for a considerable reduction of the switching RC constant with a commensurate decrease in power dissipation. The ultimate design could use the lateral-vertical structures. The AlInN/AlN/GaN technology is uniquely poised for the breakthrough in high temperature performance. We predict that the combination of these approaches will dramatically shrink the performance gap firmly establishing GaN as a superb material for power applications.

High-temperature technology platform has been developed based on AlInN/GaN heterostructures. High electron concentration in 2DEG channel of AlInN/GaN devices is remarkably stable over a broad temperature range, enabling device operation above 500 °C. The developed IC technology is based on three key elements: (1) exceptional quality AlInN/GaN heterostructure with very high carrier concentration and mobility that enables IC fast operation in a broad temperature range; (2) heterostructure field effect transistor approach that provides fully planar IC structure which is easy to scale and to combine with the other high temperature electronic components; (3) fabrication advancements including novel metallization scheme and high-k passivation/gate dielectrics, specifically developed for high temperature operation. The feasibility of the technology was demonstrated by fabrication and testing inverter and differential amplifier ICs using AlInN/GaN heterostructures. At temperature exceeding 500°C, the developed ICs show stable performance with unit-gain bandwidth above 1 MHz and internal response time 45 ns*.

We report on several key innovations to enable high performance/high reliability of nitride based FETs that include (1) the use of Perforated Channel (PC) design; (2) surface application of Low Conducting Layers (LCLs); (3) the combination of these two approaches (for achieving the ultimate power performance at the highest switching frequencies with minimum losses); (4) novel device geometries (combining the best features of lateral and vertical devices for normally-off transistors); (5) improved control of self-heating and better heat dissipation. We also review our recent results exploring the PC channel and LCL designs . Our experimental and simulation results demonstrated a sharp increase in the breakdown voltage, a large enhancement of the cutoff frequency, a better device stability and smaller spreading of the device parameters for higher yield, improved manufacturability, and smaller self-heating due to a lower thermal impedance.

Group III-Nitride based devices are expected to compete and possibly outperform state of the art silicon carbide based devices for power electronic applications. GaN, AlGaN, AlInGaN and other III-Nitride compound materials offer a very high breakdown field. Devices based on III-Nitride compounds have very high electron density and mobility in the device channel, leading to record low device on-resistance, high temperature stability and low gate capacitance enabling high switching speed and low switching loss. In order to enable III-Nitride based devices for power applications continuous efforts are underway in the area of material growth, novel power device concepts, designs, modeling and simulations.