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The measurement of the energy distribution of vacuum emitted electrons from InGaN/GaN lightemitting diodes (LEDs) has proven essential in understanding the efficiency loss mechanism known as droop. We report on the measurement and identification of a new low-energy feature in addition to the previously measured three peaks present in the electron emission spectrum from a forward biased LED. Photoemission measurements show that the two low-energy peaks correspond to photoemitted electrons from each of the p-contact metals, palladium and gold. We confirm that the mid and high-energy peaks are due to electrons which have transited the p-type region of the device and have been emitted from the semiconductor surface from the bulk ᴦ-valley or a high-energy side valley. [ABSTRACT FROM AUTHOR]

Atomic layer etching (ALE) was performed on (Al, In, Ga)N thin films using a cyclic process of alternating Cl2 gas absorption and Ar+ ion bombardment in an inductively coupled plasma etcher system. The etch damage was characterized by comparing photoluminescence of blue single quantum well light-emitting diodes before and after the etch as well as bulk resistivities of etched p-doped layers. It was found that etched surfaces were smooth and highly conformal, retaining the step-terrace features of the as-grown surface, thus realizing ALE. Longer exposures to the dry etching increased the bulk resistivity of etched surfaces layers slightly, with a damaged depth of ∼55 nm. With further optimization and damage recovery, ALE is a promising candidate for controlled etching with atomic accuracy. It was found that Al0.1Ga0.9N acts as an etch barrier for the ALE etch, making it a suitable etch to reveal buried V-defects in III-nitride light emitting diodes. [ABSTRACT FROM AUTHOR]

We report on the measurement of the lateral distribution of the junction current of an electrical biased p-n GaN diode by electron emission microscopy using a low-energy electron microscope. The vacuum level at the surface of the diode was lowered by deposition of cesium to achieve negative electron affinity, allowing overflow electrons at the surface of the biased diodes to be emitted and their spatial distribution imaged. The results were compared to the literature, and a good match with analytical solutions by Joyce and Wemple [J. Appl. Phys. 41, 3818 (1970)] was obtained. [ABSTRACT FROM AUTHOR]

Electron emission spectroscopy was performed on metalorganic chemical vapor deposition grown p-n−-n+ junctions with p-thicknesses ranging from 50 to 300 nm, doped with [Mg] = 3.5 × 1019 cm−3. By measuring the decreasing emitted electron intensity from a cesiated p-GaN surface with increasing p-thickness, we were able to extract the minority carrier diffusion length of electron in p-type GaN, Le = 26 ± 3 nm. The measured value is in good agreement with literature reported values. The extrapolated electron current at the n− region–p-GaN interface is in reasonable agreement with the simulated electron current at the interface. [ABSTRACT FROM AUTHOR]

This study aims to investigate the factors that may influence students' satisfaction on online learning platforms, the extent to which they are satisfied with their use of online learning platforms, and the effects of switching from traditional classroom instruction to online instruction on undergraduate students. This study employs a quantitative research methodology. Using a survey method, data were collected from voluntarily participating individuals. Using SPSS, the significance of the collected data was then determined. This study discovered that all variables (Internet Accessibility, University Facilities Performance, Discipline, Flexibility, and Teaching) have a positive, albeit weak, correlation with Student Satisfaction. All variables (IA, T, DP, F, and UFP) are positively significant with respect to the dependent variable (SS), but the relationship between the variables is weak. Internet accessibility (IA) and Teaching (T) were discovered to share a moderate amount of variance. Flexibility (F) and Discipline (DP) share a small degree of variance. In contrast, University Facilities Performance (UFP) has a high degree of common variant. [ABSTRACT FROM AUTHOR]

A review is given of reported trap states in the bandgaps of different polymorphs of the emerging ultrawide bandgap semiconductor Ga2O3. The commonly observed defect levels span the entire bandgap range in the three stable (β) or meta-stable polymorphs (α and ɛ) and are assigned either to impurities such as Fe or to native defects and their complexes. In the latter case, the defects can occur during crystal growth or by exposure to radiation. Such crystalline defects can adversely affect material properties critical to device operation of transistors and photodetectors, including gain, optical output, threshold voltage by reducing carrier mobility, and effective carrier concentration. The trapping effects lead to degraded device operating speed and are characterized by long recovery transients. There is still significant work to be done to correlate experimental results based on deep level transient spectroscopy and related optical spectroscopy techniques to density functional theory and the dominant impurities present in the various synthesis methods to understand the microscopic nature of defects in Ga2O3. [ABSTRACT FROM AUTHOR]

We report on c-plane InGaN/GaN single quantum well (QW) light-emitting diodes (LEDs) of different well widths (3 or 9 nm) with and without doped barriers. QW barriers were doped with the aim of reducing the internal electric field (FQW) in the QW to increase the electron-hole overlap, therefore increasing the recombination rates and resulting in the reduction of the efficiency droop. We, indeed, observed, through biased photocurrent spectroscopy, a reduction in FQW with doped barriers, with FQW being in the same direction of the p-n junction field at zero bias as opposed to the junction field for LEDs without doped barriers. Even with the improvement in the ground state wavefunction overlap, the ground state transition rate remains low for thick QWs. Transitions through excited states were observed for both thick QW LEDs with and without doped barriers. The thick QW LED without doped barriers displayed low external quantum efficiency (EQE), likely as a result of the carrier overflow due to the poor confinement of carriers in the excited states. On the other hand, for LEDs with doped barriers, the flatter band in the QW resulting from the lower FQW reduces the energy separation between the eigenstates, leading to better confinement of carriers in the excited states. With doped barriers, we demonstrated a low efficiency droop 9-nm-thick single QW LED with a peak EQE of 42% at 40 A/cm2 and an EQE of 36% at 400 A/cm2. [ABSTRACT FROM AUTHOR]

Using electron emission spectroscopy, measurement and analysis were conducted on the energy distribution of vacuum emitted electrons from an electrically driven InGaN/GaN commercial blue c-plane (peak wavelengths λ ≈ 465 nm) light emitting diode (LED) with 60 nm of p-GaN on top of the active region. The signal-to-noise ratio of semiconductor peaks is improved on the thin p-GaN LED compared to previously published data on thicker p-GaN samples and is attributed to reduced loss of electrons en route to emission into vacuum during transit through the p-GaN. This further proves that hot electrons are generated in the bulk region and not by light or other hot electron generation mechanisms at the surface. Using square root of the light output power as a proxy for the active region carrier density, n, the hot electron integrated peak intensity is shown to be proportional to n3 and, thus, is directly attributed to a 3-body Auger process. Since there are significant Auger recombination currents even at low injection current densities, it is expected that Auger recombination current will dominate over radiation recombination and Shockley–Read–Hall (SRH) currents at higher current densities. This identifies Auger recombination as the dominant cause of efficiency droop. [ABSTRACT FROM AUTHOR]

Vertical β-Ga2O3 Schottky diodes from metal-organic chemical vapor deposition (MOCVD)-grown epitaxial films are reported in this paper for high-power application devices. The Schottky diode, fabricated with a field termination structure, showed a low differential specific on-resistance of 0.67 mΩ cm2. Furthermore, the MOCVD-grown β-Ga2O3 vertical Schottky diodes exhibited a punch-through breakdown and a higher Baliga's figure-of-merit compared to those from other epitaxial growth methods of similar drift layer thickness. This suggests that the MOCVD growth, supporting high-quality epitaxy, can be promising for high-performance β-Ga2O3-based high-power devices. [ABSTRACT FROM AUTHOR]

We report on the direct measurement of hot electrons generated in the active region of blue light-emitting diodes grown by ammonia molecular beam epitaxy by electron emission spectroscopy. The external quantum efficiency of these devices is <1% and does not droop; thus, the efficiency losses from the intrinsic, interband, electron–electron–hole, or electron–hole–hole Auger should not be a significant source of hot carriers. The detection of hot electrons in this case suggests that an alternate hot electron generating process is occurring within these devices, likely a trap-assisted Auger recombination process. [ABSTRACT FROM AUTHOR]