An official website of the United States government
Wide and ultrawide-bandgap semiconductors lie at the heart of next-generation high-power, high-frequency electronics. Here, we report the growth of ultrawide-bandgap boron nitride (BN) thin films on wide-bandgap gallium nitride (GaN) by pulsed laser deposition. Comprehensive spectroscopic (core level and valence band x-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, and Raman) and microscopic (atomic force microscopy and scanning transmission electron microscopy) characterizations confirm the growth of BN thin films on GaN. Optically, we observed that the BN/GaN heterostructure is second-harmonic generation active. Moreover, we fabricated the BN/GaN heterostructure-based Schottky diode that demonstrates rectifying characteristics, lower turn-on voltage, and an improved breakdown capability (∼234 V) as compared to GaN (∼168 V), owing to the higher breakdown electrical field of BN. Our approach is an early step toward bridging the gap between wide and ultrawide-bandgap materials for potential optoelectronics as well as next-generation high-power electronics.
more »
« less
Quantifying the breakdown scale of pionless effective field theory
We use Bayesian statistics to infer the breakdown scale of pionless effective field theory in its standard power counting and with renormalization of observables carried out using the power-divergence subtraction scheme and cutoff regularization. We condition our inference on predictions of the total neutron-proton scattering cross section up next-to-next-to leading order. We quantify a median breakdown scale of approximately 1.4 mpi . The 68% degree of belief interval is [0.96, 1.69]mpi . This result confirms the canonical expectation that the pion mass is a relevant scale in low-energy nuclear physics.
more »
« less
- Award ID(s):
- 2412612
- PAR ID:
- 10621883
- Publisher / Repository:
- Physics Letters B
- Date Published:
- Journal Name:
- Physics Letters B
- Volume:
- 860
- Issue:
- C
- ISSN:
- 0370-2693
- Page Range / eLocation ID:
- 139207
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
We make order-by-order predictions of neutron–deuteron total cross sections up to next-to-next- to-leading order in pionless effective field theory. Using Bayesian methods, we infer a posterior distribution for the breakdown scale. The result shows a mode near 100 MeV, and a combined analysis with neutron–proton scattering further sharpens the inference, placing the mode close to the pion mass scale, consistent with the expected range of pionless effective field theory.vailablemore » « less
-
GaN-on-GaN vertical diode is a promising device for next-generation power electronics. Its breakdown voltage (BV) is limited by edge termination designs such as guard rings. The design space of guard rings is huge and it is difficult to optimize manually. In this paper, we propose an effective inverse design strategy to co-optimize BV and (V F Q) −1 , where BV, V F , and Q are the breakdown voltage, forward voltage, and reserve capacitive charge of the diode, respectively. Using rapid Technology Computer-Aided-Design (TCAD) simulations, neural network (NN), and Pareto front generation, a GaN-on-GaN diode is optimized within 24 hours. We can obtain structures with 200V higher BV at medium (V F Q) −1 or find a nearly ideal BV structure with 25% higher BV 2 /R on compared to the best randomly generated TCAD data.more » « less
-
Wide bandgap (WBG) and ultra-wide bandgap (UWBG)-based inverters are increasingly being adopted in More Electric Aircraft (MEA) and All Electric Aircraft (AEA) due to their ability to operate at higher switching frequencies with improved efficiency and power density. However, these advantages come with drawbacks, including increased electrical stress and exacerbation of AC losses, such as the skin effect and proximity effect. Litz wire, known for its effectiveness in mitigating these losses, is becoming a preferred conductor in highvoltage, high-frequency aerospace applications. This study investigates the breakdown voltage behavior of Litz wire insulation under square wave voltage stress across different frequencies. Twisted-pair Litz wire specimens were tested using a state-of-the-art high-voltage pulse generator with fixed rise times to emulate inverter-fed conditions. The resulting breakdown voltages were statistically analyzed using the Weibull distribution to evaluate insulation strength and failure predictability. The findings offer new insights into the insulation characteristics of Litz wire under realistic high-frequency converter stress and support the development of converter-resistant insulation systems for next-generation aerospace electrical power systems (EPS).more » « less
-
The need for high power density, flexible and light weight energy storage devices requires the use of polymer film-based dielectric capacitors. Theoretically, it has been shown that chain ends contribute adversely to electrical breakdown, resulting in low energy density in polymer capacitors. In this work, we enhanced the energy density of polymer capacitor by using well-ordered high molecular weight block copolymer (BCP), in which the chain ends are segregated to narrow zones. Cyclic homopolymers (no chain ends) and linear homopolymers having chemistry-controlled chain ends also show enhanced breakdown strength, resulting in higher energy density as compared to the linear counterparts. These novel insights into manipulating chain end distribution such as in BCPs and with molecular topology to increase the energy density of polymers will be helpful for fulfilling next-generation energy demands.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1016/j.physletb.2024.139207
