Showing papers by "Stephen J. Pearton published in 2017"

High reverse breakdown voltage Schottky rectifiers without edge termination on Ga2O3

Abstract: Vertical geometry Ni/Au-β-Ga2O3 Schottky rectifiers were fabricated on Hydride Vapor Phase Epitaxy layers on conducting bulk substrates, and the rectifying forward and reverse current-voltage characteristics were measured at temperatures in the range of 25–100 °C. The reverse breakdown voltage (VBR) of these β-Ga2O3 rectifiers without edge termination was a function of the diode diameter, being in the range of 920–1016 V (average value from 25 diodes was 975 ± 40 V, with 10 of the diodes over 1 kV) for diameters of 105 μm and consistently 810 V (810 ± 3 V for 22 diodes) for a diameter of 210 μm. The Schottky barrier height decreased from 1.1 at 25 °C to 0.94 at 100 °C, while the ideality factor increased from 1.08 to 1.28 over the same range. The figure-of-merit (VBR2/Ron), where Ron is the on-state resistance (∼6.7 mΩ cm2), was approximately 154.07 MW·cm−2 for the 105 μm diameter diodes. The reverse recovery time was 26 ns for switching from +5 V to −5 V. These results represent another impressive advanc...

High Breakdown Voltage (−201) $\beta $ -Ga2O3 Schottky Rectifiers

Abstract: $\beta $ -Ga2O3 Schottky barrier diodes were fabricated in a vertical geometry structure consisting of Ni/Au rectifying contacts without edge termination on Si-doped epitaxial layers ( $10~\mu \text{m}$ , $\text{n}\sim 4\times 10^{15}$ cm $^{-3})$ on Sn-doped bulk Ga2O3 substrates with full-area Ti/Au back Ohmic contacts The reverse breakdown voltage, ${V} _ \text {BR}$ , was a function of rectifying contact area, ranging from 1600 V at $31\times 10^{-6}$ cm2 (20- $\mu \text{m}$ diameter) to ~250 V at $22{\times }10^{-3}$ cm $^{-2}$ (053-mm diameter) The current density near breakdown was not strongly dependent on contact circumference but did scale with contact area, indicating that the bulk current contribution was dominant The lowest ON-state resistance, ${R} _\text {on}$ , was 16 $\text{m}\Omega \cdot $ cm2 for the largest diode and 25 $\text{m}\Omega \cdot $ cm2 for the 1600-V rectifier, leading to a Baliga figure-of-merit ( ${V} _\text {BR}^{2}/{R} _\text {on})$ for the latter of approximately 1024 MW $\cdot $ cm $^{-2}$ The ON-OFF ratio was measured at a forward voltage of 13 V and ranged from $3\times 10^{7}$ to $25\times 10^{6}$ for reverse biases from −5 to −40 V and showed only a small dependence on temperature in the range from 25 °C to 100 °C

Influence of High-Energy Proton Irradiation on β-Ga2O3 Nanobelt Field-Effect Transistors

Abstract: The robust radiation resistance of wide-band gap materials is advantageous for space applications, where the high-energy particle irradiation deteriorates the performance of electronic devices. We report on the effects of proton irradiation of β-Ga2O3 nanobelts, whose energy band gap is ∼4.85 eV at room temperature. Back-gated field-effect transistor (FET) based on exfoliated quasi-two-dimensional β-Ga2O3 nanobelts were exposed to a 10 MeV proton beam. The proton-dose- and time-dependent characteristics of the radiation-damaged FETs were systematically analyzed. A 73% decrease in the field-effect mobility and a positive shift of the threshold voltage were observed after proton irradiation at a fluence of 2 × 1015 cm–2. Greater radiation-induced degradation occurs in the conductive channel of the β-Ga2O3 nanobelt than at the contact between the metal and β-Ga2O3. The on/off ratio of the exfoliated β-Ga2O3 FETs was maintained even after proton doses up to 2 × 1015 cm–2. The radiation-induced damage in the β...

Tuning the thickness of exfoliated quasi-two-dimensional β-Ga2O3 flakes by plasma etching

Abstract: We demonstrated the thinning of exfoliated quasi-two-dimensional β-Ga2O3 flakes by using a reactive ion etching technique. Mechanical exfoliation of the bulk β-Ga2O3 by using an adhesive tape was followed by plasma etching to tune its thickness. Since β-Ga2O3 is not a van der Waals material, it is challenging to obtain ultra-thin flakes below a thickness of 100 nm. In this study, an etch rate of approximately 16 nm/min was achieved at a power of 200 W with a flow of 50 sccm of SF6, and under these conditions, thinning of β-Ga2O3 flakes from 300 nm down to ∼60 nm was achieved with smooth morphology. We believe that the reaction between SF6 and Ga2O3 results in oxygen and volatile oxygen fluoride compounds, and non-volatile compounds such as GaFX that can be removed by ion bombardment. The opto-electrical properties were also characterized by fabricating solar-blind photodetectors using the plasma-thinned β-Ga2O3 flakes; these detectors showed fast response and decay with excellent responsivity and selectivity. Our results pave the way for tuning the thickness of two-dimensional materials by using this scalable, industry-compatible dry etching technique.

Energy band offsets of dielectrics on InGaZnO4

Abstract: Thin-film transistors (TFTs) with channels made of hydrogenated amorphous silicon (a-Si:H) and polycrystalline silicon (poly-Si) are used extensively in the display industry. Amorphous silicon continues to dominate large-format display technology, but a-Si:H has a low electron mobility, μ ∼ 1 cm2/V s. Transparent, conducting metal-oxide materials such as Indium-Gallium-Zinc Oxide (IGZO) have demonstrated electron mobilities of 10–50 cm2/V s and are candidates to replace a-Si:H for TFT backplane technologies. The device performance depends strongly on the type of band alignment of the gate dielectric with the semiconductor channel material and on the band offsets. The factors that determine the conduction and valence band offsets for a given material system are not well understood. Predictions based on various models have historically been unreliable and band offset values must be determined experimentally. This paper provides experimental band offset values for a number of gate dielectrics on IGZO for nex...

1.5 MeV electron irradiation damage in β-Ga2O3 vertical rectifiers

Abstract: Vertical rectifiers fabricated on epi Ga2O3 on bulk β-Ga2O3 were subject to 1.5 MeV electron irradiation at fluences from 1.79 × 1015 to 1.43 × 1016 cm−2 at a fixed beam current of 10−3 A. The electron irradiation caused a reduction in carrier concentration in the epi Ga2O3, with a carrier removal rate of 4.9 cm−1. The 2 kT region of the forward current–voltage characteristics increased due to electron-induced damage, with an increase in diode ideality factor of ∼8% at the highest fluence and a more than 2 order of magnitude increase in on-state resistance. There was a significant reduction in reverse bias current, which scaled with electron fluence. The on/off ratio at −10 V reverse bias voltage was severely degraded by electron irradiation, decreasing from ∼107 in the reference diodes to ∼2 × 104 for the 1.43 × 1016 cm−2 fluence. The reverse recovery characteristics showed little change even at the highest fluence, with values in the range of 21–25 ns for all rectifiers.

Inductively coupled plasma etch damage in (-201) Ga2O3 Schottky diodes

Abstract: Bulk, single-crystal Ga2O3 was etched in BCl3/Ar inductively coupled plasmas as a function of ion impact energy. For pure Ar, the etch rate (R) was found to increase with ion energy (E) as predicted from a model of ion enhanced sputtering by a collision-cascade process, R ∝(E0.5 – ETH0.5), where the threshold energy for Ga2O3, ETH, was experimentally determined to be ∼75 eV. When BCl3 was added, the complexity of the ion energy distribution precluded, obtaining an equivalent threshold. Electrically active damage introduced during etching was quantified using Schottky barrier height and diode ideality factor measurements obtained by evaporating Ni/Au rectifying contacts through stencil masks onto the etched surfaces. For low etch rate conditions (∼120 A min−1) at low powers (150 W of the 2 MHz ICP source power and 15 W rf of 13.56 MHz chuck power), there was only a small decrease in reverse breakdown voltage (∼6%), while the barrier height decreased from 1.2 eV to 1.01 eV and the ideality factor increased ...

Annealing of dry etch damage in metallized and bare (-201) Ga2O3

Abstract: The surface of single-crystal (-201) oriented β-Ga2O3 was etched in BCl3/Ar inductively coupled plasmas under conditions (an excitation frequency of 13.56 MHz, a source power of 400 W, and a dc self-bias of −450 V) that produce removal rates of ∼700 A min−1. Annealing at 400 and 450 °C was carried out after etching on Ni/Au Schottky diodes formed on the surface either before or after the annealing step. Current–voltage (I–V) measurements were used to extract the Schottky barrier height (Φ), diode ideality factor (n), and reverse breakdown voltage (VRB) for plasma damaged diodes after annealing. Annealing at 450 °C was found to essentially restore the values of Φ, n, and VRB to their reference (unetched) values on samples metallized after etching and annealing. Thermal annealing at either temperature of metallized diodes degraded their reverse breakdown voltage, showing that Ni/Au is not stable on β-Ga2O3 at these temperatures. Photoluminescence revealed a decrease in total emission intensity in the near b...

Ohmic contacts on n-type β-Ga2O3 using AZO/Ti/Au

Abstract: AZO interlayers between n-Ga2O3 and Ti/Au metallization significantly enhance Ohmic contact formation after annealing at ≥ 300°C. Without the presence of the AZO, similar anneals produce only rectifying current-voltage characteristics. Transmission Line Measurements of the Au/Ti/AZO/Ga2O3 stacks showed the specific contact resistance and transfer resistance decreased sharply from as-deposited values with annealing. The minimum contact resistance and specific contact resistance of 0.42 Ω-mm and 2.82 × 10-5 Ω-cm2 were achieved after a relatively low temperature 400°C annealing. The conduction band offset between AZO and Ga2O3 is 0.79 eV and provides a favorable pathway for improved electron transport across this interface.

Improvement of Ohmic contacts on Ga2O3 through use of ITO-interlayers

Abstract: The use of ITO interlayers between Ga2O3 and Ti/Au metallization is shown to produce Ohmic contacts after annealing in the range of 500–600 °C. Without the ITO, similar anneals do not lead to linear current–voltage characteristics. Transmission line measurements were used to extract the specific contact resistance of the Au/Ti/ITO/Ga2O3 stacks as a function of annealing temperature. Sheet, specific contact, and transfer resistances all decreased sharply from as-deposited values with annealing. The minimum transfer resistance and specific contact resistance of 0.60 Ω mm and 6.3 × 10−5 Ω cm2 were achieved after 600 °C annealing, respectively. The conduction band offset between ITO and Ga2O3 is 0.32 eV and is consistent with the improved electron transport across the heterointerface.

Conduction and valence band offsets of LaAl2O3 with (−201) β-Ga2O3

Abstract: Wide bandgap dielectrics are needed as gate insulators and surface passivation layers on the emerging electronic oxide Ga2O3. X-ray photoelectron spectroscopy was used to determine the valence band offset at LaAl2O3 (LAO)/β-Ga2O3 heterointerfaces. LaAl2O3 was deposited by RF magnetron sputtering onto bulk Ga2O3 crystals. The bandgaps of the materials were determined by reflection electron energy loss spectroscopy to be 4.6 eV for Ga2O3 and 6.4 eV for LAO. The valence band offset was determined to be −0.21 ± 0.02 eV (staggered gap, type II alignment) for LAO on Ga2O3. This leads to a conduction band offset of 2.01 ± 0.60 eV for LaAO with Ga2O3. Thus, LAO provides excellent electron confinement but not hole confinement in LAO/Ga2O3 heterostructures.

Band alignment of atomic layer deposited SiO 2 and HfSiO 4 with (\bar{2}01) β-Ga 2 O 3

Abstract: The valence band offset at both SiO2/β-Ga2O3 and HfSiO4/β-Ga2O3 heterointerfaces was measured using X-ray photoelectron spectroscopy. Both dielectrics were deposited by atomic layer deposition (ALD) onto single-crystal β-Ga2O3. The bandgaps of the materials were determined by reflection electron energy loss spectroscopy as 4.6 eV for Ga2O3, 8.7 eV for Al2O3 and 7.0 eV for HfSiO4. The valence band offset was determined to be 1.23 ± 0.20 eV (straddling gap, type I alignment) for ALD SiO2 on β-Ga2O3 and 0.02 ± 0.003 eV (also type I alignment) for HfSiO4. The respective conduction band offsets were 2.87 ± 0.70 eV for ALD SiO2 and 2.38 ± 0.50 eV for HfSiO4, respectively.

Pt-AlGaN/GaN Hydrogen Sensor With Water-Blocking PMMA Layer

Abstract: One of the biggest issues with GaN-based hydrogen sensors is their sensitivity to humidity in the ambient. We demonstrate that encapsulation of Pt-AlGaN/GaN Schottky diode with poly(methyl methacrylate) (PMMA) provides effective mitigation of the effects of water. Without PMMA encapsulation, the absolute current signal for detection of 500 ppm of H2 was decreased by a factor of 8 in the presence of water. By sharp contrast, encapsulated diodes show no decrease in response in the presence of water. The relative current changes are of the order $2.8 \times 10^{5}$ % when 500 ppm H2 is introduced to the surface of bare or PMMA encapsulated diodes in the absence of water or to encapsulated diode in the presence of water. Detection limits of ~ 100 ppm H2 (0.01% by volume) were obtained with standard forward bias detection mode at 1.3 V.

Point defects controlling non-radiative recombination in GaN blue light emitting diodes: Insights from radiation damage experiments

Abstract: The role of Shockley-Read-Hall non-radiative recombination centers on electroluminescence (EL) efficiency in blue multi-quantum-well (MQW) 436 nm GaN/InGaN light emitting diodes (LEDs) was examined by controlled introduction of point defects through 6 MeV electron irradiation. The decrease in the EL efficiency in LEDs subjected to irradiation with fluences above 5 × 1015 cm−2 was closely correlated to the increase in concentration of Ec-0.7 eV electron traps in the active MQW region. This increase in trap density was accompanied by an increase in the both diode series resistance and ideality factor (from 1.4 before irradiation to 2.1 after irradiation), as well as the forward leakage current at low forward voltages that compromise the injection efficiency. Hole traps present in the blue LEDs do not have a significant effect on EL changes with radiation because of their low concentration.

Defects responsible for lifetime degradation in electron irradiated n-GaN grown by hydride vapor phase epitaxy

Abstract: The effects of room temperature 6 MeV electron irradiation on the donor concentration, deep trap spectra, and diffusion lengths of nonequilibrium charge carriers were studied for undoped n-GaN grown by hydride vapor phase epitaxy. Changes in these parameters begin at a threshold electron fluence of 5 × 1015 cm−2. The diffusion lengths after this fluence decrease by a factor of 3, accompanied by a drastic increase in the density of deep electron traps with the level near Ec – 1 eV. There is a strong correlation between the changes in the density of these traps and the diffusion length of irradiated n-GaN, indicating that these centers control the lifetime in radiation damaged n-GaN. This is in sharp contrast to the starting material, where the lifetimes are controlled by other deep electron traps at Ec – 0.56 eV. The concentration of the latter is not strongly affected by high energy electron irradiation.

Inductively coupled plasma etching of bulk, single-crystal Ga2O3

Abstract: High ion density dry etching of bulk single-crystal β-Ga2O3 was carried out as a function of source power (100–800 W), chuck power (15–400 W), and frequency (13.56 or 40 MHz) in inductively coupled plasma (ICP) systems using Cl2/Ar or BCl3/Ar discharges. The highest etch rate achieved was ∼1300 A min−1 using 800 W ICP source power and 200 W chuck power (13.56 MHz) with either Cl2/Ar or BCl3/Ar. This is still a comfortably practical set of conditions, where resist reticulation does not occur because of the effective He backside cooling of the sample in the tool and the avoidance of overly high powers in systems capable of 2000 W of source power. The etching is ion-assisted and produces anisotropic pattern transfer. The etched surface may become oxygen-deficient under strong ion-bombardment conditions. Schottky diodes fabricated on these surfaces show increased ideality factors (increasing from 1.00 to 1.29 for high power conditions) and reduced barrier heights (1.1 on reference diodes to 0.86 eV for etched...

Changes in electron and hole traps in GaN-based light emitting diodes from near-UV to green spectral ranges

Abstract: Deep electron and hole traps were studied by admittance spectroscopy (AS) and deep level transient spectroscopy (DLTS) with electrical and optical (ODLTS) injection for GaN-based multi-quantum-well (MQW) light emitting diodes (LEDs) operating in the near-UV (385–390 nm), blue (445 nm), and green (515 nm) spectral regions. AS spectra were dominated by freezing out of Mg acceptors at temperatures around 150 K, by shallow centers in the MQW region, and, for green LEDs, by deeper electron traps with a level near Ec − 0.27 eV located in the MQW region. DLTS spectra showed electron traps with levels Ec − 0.8 eV (NUV), Ec − 0.5 eV (blue), Ec − 0.6 eV (blue and NUV), and Ec − 0.27(green LEDs). In ODLTS, hole traps near Ev + 0.75 eV (NUV), Ev + 0.65 eV (blue), and Ev + 0.45 eV (green LEDs) originating in the quantum well (QW) region were detected (the QW character was confirmed by using excitation light that generated electron-hole pairs only within the QWs). The levels of the electron and hole traps in LED struct...

Low dose 60Co gamma-irradiation effects on electronic carrier transport and DC characteristics of AlGaN/GaN high-electron-mobility transistors

Abstract: The impact of internal irradiation with secondary Compton electrons, generated by gamma-photons, on the characteristics of III-N/GaN-based devices was explored N-channel AlGaN/GaN high-electron-mobility transistors (HEMTs) were exposed to gamma-radiation from a 60Co source for doses up to 600 Gy Temperature-dependent electron beam-induced current (EBIC) was employed to measure minority carrier transport properties For low doses below ∼250 Gy, the minority carrier diffusion length in AlGaN/GaN HEMTs is shown to increase by about 40% This increase is likely due to longer minority carrier lifetime induced by internal Compton electron irradiation An associated decrease in activation energy, extracted from temperature-dependent EBIC, was also found The obtained increase in transconductance and decrease in gate leakage current indicate an improvement in performance of the devices after low doses of irradiation For high doses of gamma-irradiation, above ∼300 Gy, the performance of HEMTs showed a d

Rapid detection of cardiac troponin I using antibody-immobilized gate-pulsed AlGaN/GaN high electron mobility transistor structures

Abstract: We report a comparison of two different approaches to detecting cardiac troponin I (cTnI) using antibody-functionalized AlGaN/GaN High Electron Mobility Transistors (HEMTs). If the solution containing the biomarker has high ionic strength, there can be difficulty in detection due to charge-screening effects. To overcome this, in the first approach, we used a recently developed method involving pulsed biases applied between a separate functionalized electrode and the gate of the HEMT. The resulting electrical double layer produces charge changes which are correlated with the concentration of the cTnI biomarker. The second approach fabricates the sensing area on a glass slide, and the pulsed gate signal is externally connected to the nitride HEMT. This produces a larger integrated change in charge and can be used over a broader range of concentrations without suffering from charge-screening effects. Both approaches can detect cTnI at levels down to 0.01 ng/ml. The glass slide approach is attractive for inexpensive cartridge-type sensors.

Degradation-induced low frequency noise and deep traps in GaN/InGaN near-UV LEDs

Abstract: Electrical stressing of near-UV (peak wavelength 390–395 nm) multi-quantum-well GaN/InGaN light emitting diodes at a high drive current of 650 mA and elevated temperature of 110 °C causes a significant degradation in external quantum efficiency (EQE), correlated with the formation of nitrogen interstitial-related electron traps at Ec − 0.8 eV. The dependence of the spectral density of current noise SI on forward current If showed two regions prior to accelerated aging, with SI ∼ If due to the current flow via localized leakage channels (presumably dislocations) and SI ∼ If2 related to the generation-recombination noise caused by the Ec − 0.8 eV states and Ev + 0.75 eV hole traps in the space charge region. Electrical stress for <922 h did not change the EQE but gradually increased both reverse and forward leakage current. This was accompanied by a gradual increase in the density of the hole traps, but not the electron traps. The mechanism appears to be the displacement of Ga and In atoms, with the interst...

Deep electron and hole traps in electron-irradiated green GaN/InGaN light emitting diodes

Abstract: Deep electron and hole trap spectra and electroluminescence (EL) efficiency of green multi-quantum-well (MQW) GaN/InGaN light emitting diodes were measured before and after 6 MeV electron irradiation. Starting with a fluence of 5 × 1015 cm−2, electron irradiation increased the concentration of existing electron traps with levels at Ec−0.5 eV and introduced new electron traps with levels near Ec−1 eV. The latter are the well known radiation defects formed in the GaN barriers of the GaN/InGaN MQW region. The degradation of the EL efficiency after irradiation correlates with changes of the Ec−0.5 eV and Ec−1 eV electron trap density, suggesting these are effective non-radiative recombination centers. By sharp contrast, the concentration of the dominant hole traps with levels near Ev+0.45 eV decreased after, which eliminates these from the role of Shockley-Read-Hall defects actively participating in recombination. © 2017 The Electrochemical Society. [DOI: 10.1149/2.0131710jss] All rights reserved.

Effect of nanopillar sublayer embedded with SiO2 on deep traps in green GaN/InGaN light emitting diodes

Abstract: The effect of a layer of GaN nanopillars with SiO2 nanoparticles inserted into the n+-GaN contact Layer on the electrical properties, electroluminescence (EL) and photoluminescence (PL), admittance spectra, and deep trap spectra of green multi-quantum-well GaN/InGaN light emitting diodes (LEDs) grown by metalorganic chemical vapor deposition (MOCVD) on patterned sapphire substrates is reported. The PL and EL intensities for these SiO2 LEDs are measurably enhanced compared with reference to LEDs without the nanopillar sublayer. This correlates with the decrease in the SiO2 LEDs of the concentration of 0.25 eV electron traps and 0.45 eV hole traps, both located in the InGaN QWs.

Current relaxation analysis in AlGaN/GaN high electron mobility transistors

Abstract: Current relaxations in AlGaN/GaN high electron mobility transistors (HEMTs) often show a broad spread of relaxation times. These are commonly linked to the ionization energies of the traps in different regions of the devices and the relaxations are assumed to be exponential. To explain the observed spread of parameters, the presence of multiple centers is assumed. However, in actual spectra, only a few main peaks in the lifetimes distributions are observed, with considerable broadening of the peaks. In this paper, the authors examine the possible origin of the relaxation time broadening, including the presence of disorder giving rise to extended exponential decays and to physical broadening of discrete levels into bands. The latter is modeled by Gaussian broadening of the logarithm of relaxation time. The authors demonstrate the analysis of the peak positions and widths of the first derivative of the current transient by the logarithm in time, which is quite useful in deriving the relevant broadening para...

Extraction of Migration Energies and Role of Implant Damage on Thermal Stability of Deuterium in Ga2O3

Abstract: Deuterium was incorporated in bulk single crystal β-Ga2O3 samples by either ion implantation (100 keV, 1015 cm−2) or plasma exposure (up to 270°C, 30 mins) of single-crystal β-Ga2O3 and then its stability was examined as a function of annealing temperature. The mechanisms in both cases were extracted by fitting the experimental depth profiles using models within the Florida Object Oriented Process Simulator (FLOOPS) code. In the case of incorporation by implantation, annealing causes the deuterium to migrate toward the surface with simultaneous trapping at the residual implant damage. In the case of plasma incorporation where there is no residual damage, annealing causes outgassing of the deuterium from the surface, mediated through molecule formation. Very good fits to the experimental data are achieved by integrating physics of the outdiffusion mechanisms into the FLOOPS code. The rate constants and diffusivities used for the simulation were found to follow an Arrhenius dependence, with an activation energy for outdiffusion of deuterium of 1.22 eV and 2.58 eV for the release rate of deuterium from trap sites in the implanted case.

Temperature and Humidity Dependence of Response of PMGI-Encapsulated Pt-AlGaN/GaN Diodes for Hydrogen Sensing

Abstract: Polydimethylglutarimide (PMGI), a photosensitive positive type resin used in photoresists, is shown to be an effective moisture barrier for mitigating the effect of humidity on the sensitivity of Pt-AlGaN/GaN Schottky diodes for hydrogen detection. The maximum relative current change observed in PMGI-encapsulated diodes forward biased at 1.3 V and exposed to 500 ppm of dry or humid H2 is identical within experimental error over the temperature range 25 °C–300 °C and peaks at 200 °C in both cases ( $4.4\times 10^{6}$ % increase compared with the current under N2 ambient). Unencapsulated diodes exhibit a decrease of approximately one ninth of the current signal for detection of 500 ppm of H2 in the presence of water. The PMGI is easily spun-on to the sensors, and does not degrade until temperatures of 335 °C or higher, making it a suitable moisture barrier for most hydrogen sensing applications.

Electron irradiation of near‐UV GaN/InGaN light emitting diodes

Abstract: Irradiation with 6 MeV electrons of near-UV (peak wavelength 385–390 nm) multi-quantum-well (MQW) GaN/InGaN light emitting diodes (LEDs) causes an increase in density of deep electron traps near Ec−0.8 and Ec−1 eV, and correlates to a 90% decrease of electroluminescence (EL) efficiency after a fluence of 1.1 × 1016 cm−2. The likely origin of the EL efficiency decrease is this increase in concentration of the Ec −0.8 eV and Ec −1 eV traps.