Temperature Dependent Low-Frequency Noise Characteristics of NiOx_x/Ga2_2O3_3 p-n Heterojunction Diodes

We report on the temperature dependence of the low-frequency electronic noise in NiO$_x$/Ga$_2$O$_3$ p-n heterojunction diodes. The noise spectral density is of the 1/f-type near room temperature but shows signatures of Lorentzian components at elevated temperatures and at higher current levels (f is the frequency). We observed an intriguing non-monotonic dependence of the noise on temperature near T = 380$^\circ$ K. The Raman spectroscopy of the device structure suggests material changes, which results in reduced noise above this temperature. The normalized noise spectral density in such diodes was determined to be on the order of 10$^{-14}$ cm$^2$/Hz (f = 10 Hz) at 0.1 A/cm$^2$ current density. In terms of the noise level, NiO$_x$/Ga$_2$O$_3$ p-n diodes occupy an intermediate position among devices of various designs implemented with different ultra-wide-band-gap (UWBG) semiconductors. The obtained results are important for understanding the electronic properties of the UWBG heterojunctions and contribute to the development of noise spectroscopy as the quality assessment tool for new electronic materials and device technologies.Comment: 18 pages, 6 figure

Low-Frequency Electronic Noise in the Aluminum Gallium Oxide Schottky Barrier Diodes

We report on the low-frequency electronic noise in (Al$_x$Ga$_{1-x}$)$_2$O$_3$ Schottky barrier diodes. The noise spectral density reveals 1/f dependence, characteristic of the flicker noise, with superimposed Lorentzian bulges at the intermediate current levels (f is the frequency). The normalized noise spectral density in such diodes was determined to be on the order of 10$^{-12}$ cm$^2$/Hz (f=10 Hz) at 1 A/cm$^2$ current density. At the intermediate current regime, we observed the random telegraph signal noise, correlated with the appearance of Lorentzian bulges in the noise spectrum. The random telegraph signal noise was attributed to the defects near the Schottky barrier. The defects can affect the local electric field and the potential barrier, and correspondingly, impact the electric current. The obtained results help to understand noise in Schottky barrier diodes made of ultra-wide-band-gap semiconductors and can be used for the material and device quality assessment.Comment: 16 pages, 6 figure

Ultrafast Control of Excitonic Rashba Fine Structure by Phonon Coherence in the Metal Halide Perovskite CH3NH3PbI3

We discover hidden Rashba fine structure in CH3NH3PbI3 and demonstrate its quantum control by vibrational coherence through symmetry-selective vibronic (electron-phonon) coupling. Above a critical threshold of a single-cycle terahertz pump field, a Raman phonon mode distinctly modulates the middle excitonic states with persistent coherence for more than ten times longer than the ones on two sides that predominately couple to infrared phonons. These vibronic quantum beats, together with first-principles modeling of phonon periodically modulated Rashba parameters, identify a threefold excitonic fine structure splitting, i.e., optically forbidden, degenerate dark states in between two bright ones with a narrow, similar to 3 nm splitting. Harnessing of vibronic quantum coherence and symmetry inspires light-perovskite quantum control and sub-THz-cycle Rashba engineering of spin-split bands for ultimate multifunction device

Terahertz Second Harmonic Generation Form Nb3Sn Superconductor

Symmetry breaking phenomena in superconductors is a fascinating field of study. Here we report the observation of Terahertz second harmonic generation (T-SHG) from Nb3Sn superconductor. T-SHG can be used as a tool to detect symmetry breaking inside superconducting fluid. Conventionally SHG cannot be observed in superconductors with inversion symmetry. Here we perturb superconducting fluid using Terahertz electromagnetic radiation and break the inversion symmetry to generate T-SHG.</p

Design and optimization of edge termination techniques for β-Ga2O3/GaN heterojunction for p-n power diodes using TCAD simulation

We report systematic design, calibration, and optimization of GaN/β-Ga2O3 p-n power diode for kV-class operation. The ideal device structure showed a breakdown voltage (BV) of 1.37 kV while a simple mesa isolated reference device showed a BV of 300 V. In real device fabrication, the ideal device structure is harder to achieve, and the reference device structure is more common in usage. However, the high voltage capability of the reference device can be enhanced using different edge termination (ET) techniques. Four ET techniques have been adopted to increase the device BV, namely, bevel mesa, step mesa, deeply etched mesa, and p-GaN guard ring. Ideal device BV can be achieved from deeply etched mesa and p-GaN guard ring ETs. The step mesa can give 41% of the ideal device value while bevel mesa is effective for 85%. All the values have been demonstrated with 5 µm drift region where the BV is scalable with changing the drift region thickness. β-Ga2O3 based bipolar high voltage and high-power devices can use this work as a guidance to improve their performance

Temperature Dependence of Low‐Frequency Noise Characteristics of NiOx/β‐Ga2O3 p–n Heterojunction Diodes

Abstract Temperature dependence of the low‐frequency electronic noise in NiOx/β‐Ga2O3 p–n heterojunction diodes is reported. The noise spectral density is of the 1/f‐type near room temperature but shows signatures of Lorentzian components at elevated temperatures and at higher current levels (f is the frequency). It is observed that there is an intriguing non‐monotonic dependence of the noise on temperature near T = 380 K. The Raman spectroscopy of the device structure suggests material changes, which results in reduced noise above this temperature. The normalized noise spectral density in such diodes is determined to be on the order of 10−14 cm2 Hz−1 (f = 10 Hz) at 0.1 A cm−2 current density. In terms of the noise level, NiOx/β‐Ga2O3 p–n diodes perform excellently for new technology and occupy an intermediate position among devices of various designs implemented with different ultra‐wide‐bandgap semiconductors. The obtained results are important for understanding the electronic properties of NiOx/β‐Ga2O3 heterojunctions and contribute to the development of noise spectroscopy as the quality assessment tool for new electronic materials and device technologies