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Abstract
Irradiation damage in In0.53Ga0.47As p-i-n photodiodes by 1 MeV fast neutrons has been studied as a function of fluence for the first time, and the results are discussed in this paper. The degradation of the electrical and optical performance of diodes increases with increasing fluence. The induced lattice defects in the In0.53Ga0.47As epitaxial layers and the InP substrate are studied by Deep Level Transient Spectroscopy (DLTS) methods. In the In0.53Ga0.47As epitaxial layers, hole and electron capture levels are induced by irradiation. The influence of the type of radiation source on the device degradation is then discussed by comparison to 1 MeV electrons with respect to the numbers of knock-on atoms and the nonionizing energy loss (NIEL). The radiation source dependence of performance degradation is attributed to the difference of mass between the two irradiating particles and the probability of nuclear collision for the formation of lattice defects.
... Being one of the dominant radiation-induced effects, the DD effect on optoelectronic devices has been addressed by many experimental and theoretical studies. DD-induced degradations on the parameters of devices, such as optical output power [4][5][6], optical transmission [7,8], optical gain [9][10][11][12], and dark current and responsivity [13][14][15][16], are tested and analyzed. Because the purpose of these studies is to investigate device degradation, radiation-induced system performance degradation is not involved. ...
Displacement damage (DD) effect induced bit error ratio (BER) performance degradations in on–off keying (OOK), pulse position modulation (PPM), differential phase-shift keying (DPSK), and homodyne binary phase shift keying (BPSK) based systems were simulated and discussed under 1 MeV neutron irradiation to a total fluence of 1 × 10 12 n / cm 2 in this paper. Degradation of main optoelectronic devices included in communication systems were analyzed on the basis of existing experimental data. The system BER degradation was subsequently simulated and the variations of BER with different neutron irradiation location were also achieved. The result shows that DD on an Er-doped fiber amplifier (EDFA) is the dominant cause of system degradation, and a BPSK-based system performs better than the other three systems against DD. In order to improve radiation hardness of communication systems against DD, protection and enhancement of EDFA are required, and the use of a homodyne BPSK modulation scheme is a considered choice.
Indium phosphide is widely used in electronics and photovoltaic devices due to its high electro-optical conversion efficiency, high electron mobility, and good radiation resistance. Defects are the main limitation for the performance of InP devices. In this work, based on hybrid functional with finite size correction, electronic properties of intrinsic and H-related defects have been investigated in InP. We found that PIn defect is the most stable intrinsic defect with the lowest formation energy. Defect signals detected experimentally are defined by our calculated results. Experimentally observed electron traps with the energy level of EC − 0.66 eV and EC − 0.68 eV are ascribed to the transition level ɛ(−1/−2) and ɛ(−2/−3) of In vacancies. The hydrogenated vacancies in InP have been systematically reported in the present work. Formation energies of H-related defects indicate that hydrogen atoms prefer to bind to In vacancy than P vacancy. The formation energy of In vacancy decreases with the addition of H, while that of P vacancy increases. For hydrogenated In vacancies, it captures fewer electrons than bare In vacancies when the Fermi level is close to CBM. Especially for the VIn − 3H structure, it is 0 charge state in all Fermi levels so that it will not tend to capture electron or hole. Our work is helpful to explain experimental phenomena and radiation-induced damages and improve the performance of InP devices.
We report the behaviour of the dark current and gain characteristics of Si- and GaN-based avalanche photodiodes (APDs) irradiated by fast neutrons. For Si-based APDs, the dark current increases with the increase of neutron fluence, indicating that the avalanche property has been seriously affected. The gain values of Si-based APD slightly increase after irradiation by a low neutron fluence of 1.0 × 10¹² cm⁻², while the device exhibits gain degradation as the fluence increases to 1.0 × 10¹³ cm⁻² or even above at high reverse bias voltage, unlike the previous studies where only degradation was observed. The steep increase of dark current and gain when approaching the breakdown voltage after neutron irradiation indicate that the avalanche property is almost unaffected for GaN-based APDs. Furthermore, we infer that the optical absorption between acceptor state and conduction band in the p-type layer plays an important role in influencing the change of dark current and gain at high reverse bias voltage. The findings not only enrich the understanding of neutron irradiation effect on Si- and GaN-based APDs, but also experimentally prove that GaN-based APDs hold better radiation resistance than Si-based devices.
The displacement damage effects on indium gallium arsenide (InGaAs) p-i-n photodetectors induced by neutron at China Spallation Neutron Source (CSNS) are analyzed. The irradiation fluence range from 1.0 × 10¹¹ to 3.6 × 10¹³ cm−2. The InGaAs p-i-n photodetector under investigation were fabricated with top illumination structure. The forward and reverse bias current–voltage (I-V) under the dark environment are measured before and after neutron radiation at room environment. Experiment results for different bias conditions and different irradiation flux were compared. The mechanism of displacement damage effects on the I-V characters of InGaAs p-i-n photodetectors are analyzed combined with TCAD simulation. The annealing effects on InGaAs p-i-n photodetectors are also investigated.
The effect of traps to C–V and I–V plots of InP/InGaAs heterostructure with 3 MeV proton irradiation at different fluences has been discussed. After proton irradiation, the total reverse capacitance increases, which does not only include the variation of the depletion region width, but also the charging and discharging effect of traps. The total actual traps density NSS of InP/InGaAs heterostructure could reach 13 orders of trap density, which is from the peak under reverse bias. The forward current is dominated by recombination current at low voltage and by the tunneling current at high voltage. The tunneling current and trap-assisted tunneling current are dominant in the reverse current.
The performance of the SCIAMACHY detectors has been monitored since launch. Only minor degradation of the silicon-based UV–Vis detectors and the lattice-matched InGaAs NIR detector is observed. The degradation of the NIR extended-wavelength InGaAs detector arrays, however, which are used for the first time in a space-based remote sensing application, is unexpectedly large. The degradation of individual detector pixels is abrupt and mostly leads to excessively high (spread in) dark current. Evidence is presented that non-ionizing radiation due to trapped-protons leads to displacement damage to the InGaAs detector material. The current degradation rate leads to a loss of approximately 50 out of 1024 pixels per channel per year.
The effect of irradiation with fast reactor neutrons at an effective energy of 1 MeV and a fluence within Φ = 1 × 1014−5 × 1015 n/cm2 on the photoelectric parameters of p-n-InSe homojunctions obtained in direct optical contact between p- and n-type semiconductors has been studied. The exposure to fast neutrons leads to an increase in the rectification coefficient
and the diode ideality factor of the current-voltage characteristics with increasing neutron dose. No significant changes
have been observed in the photosensitivity spectra of p-n-InSe structures irradiated to various doses, which allows these structures to be recommended for the creation of radiation-resistant
photodetectors.
The annealing behavior of the reverse bias current-voltage curves of 1 MeV electron irradiated In(0.53)Ga(0.47)As photodiodes has been measured at 300 K. The observed decay is shown to be correlated with the reduction of the E2 peak height with time, as measured by deep level transient spectroscopy. The reverse current is found to decay with a logarithmic time dependence, which can be explained by a model in which the annealing of the E2 defects is controlled by a distribution of thermal energy barriers.
Low-temperature photoluminescence in InGaAs/GaAs strained quantum wells shows the appearance, upon deuterium irradiation, of two bands at energies below the heavy-hole free exciton. The deeper band is due to recombination at a deuterium impurity (or at a deuterium-defect complex), while the shallower band is attributed to an exciton bound to the deuterium-related state. The binding energies of these two bands depend on alloy composition and well width and show a maximum for finite well width values as expected by theoretical calculations. The absence of these bands in samples irradiated with helium shows that the two bands are related to deuterium atoms in the samples rather than to recombination centres due to the irradiation procedure. Thermal annealing treatments indicate that the dissociation energy of the deuterium-related radiative state is comparable to that measured in GaAs for complexes formed by deuterium and deep traps.
The reverse dark current‐voltage (dark I‐V) curves of InGaAs photodiodes have been measured as a function of temperature following irradiation with 1‐MeV electrons. Prior to irradiation, the I‐V curves are well described by a diffusion term alone indicating that the junctions are of good quality. Irradiation produces a large increase in the generation current which can be modelled as resulting from a single defect center with an energy E c -0.29 eV. Such a defect center called E2 has been detected using deep level transient spectroscopy.
Irradiation damage in n<sup>+</sup>-Si/p<sup>+</sup>-Si<sub>1-x
</sub>Ge<sub>x</sub>/n-Si epitaxial heterojunction bipolar transistors
(HBTs) by 1-MeV fast neutrons is studied as a function of fluence and
germanium content for the first time. The degradation of the electrical
performance of HBTs by irradiation increases with increasing fluence,
while it decreases with increasing germanium content. The induced
lattice defects in the base and the collector regions are studied by
DLTS methods. In the base region, electron capture levels associated
with interstitial boron are induced by irradiation, while two electron
capture levels corresponding to the E centers and the divacancy are
formed in the collector region. The degradation of device performance is
then correlated with simulations of numbers of knock-on atoms. In order
to examine the recovery behavior, isochronal thermal annealing is
carried out for temperatures ranging from 75 to 300°C. Based on the
recovery of electrical performance, it is pointed out that the electron
capture levels induced in the base and collector regions are mainly
responsible for the increase of base current and the decrease of
collector current
The irradiation damage in n/sup +/-Si/p/sup +/-Si/sub 1-x/Ge/sub x/ epitaxial diodes and n/sup +/-Si/p/sup +/-Si/sub 1-x/Ge/sub x//n-Si epitaxial heterojunction bipolar transistors (HBTs) by fast neutrons and MeV electrons is studied as a function of fluence and germanium content for the first time. The degradation of the electrical performance of both diodes and HBTs by irradiation increases with increasing fluence, while it decreases with increasing germanium content. The damage coefficient of reverse current for x=0.12 and 0.16 diodes irradiated by neutrons is calculated to be 6.2/spl times/10/sup -21/ and 5.5/spl times/10/sup -21/ n/sup -1/ A cm/sup 2/, respectively. That of h/sub FE/ for electron-irradiated x=0.08, 0.12 and 0.16 HBTs is 7.6/spl times/10/sup -16/, 2.7/spl times/10/sup -16/ and 1.6/spl times/10/sup -16/ s/sup -1/ cm/sup 2/ respectively.< >
The degradation of
n<sup>+</sup>-Si/p<sup>+</sup>-Si<sub>1-x</sub>Ge<sub>x</sub> diodes,
which are fabricated on strained Si<sub>1-x</sub>Ge<sub>x</sub>
epitaxial layers grown on conventional p-type Si substrates, is
investigated through the study of the annealing behaviour of forward and
reverse diode current and the electrically active defects induced in the
Si<sub>1-x</sub>Ge<sub>x</sub> epitaxial layers. The diodes are
irradiated at room temperature with 1-MeV electrons with fluences
ranging from 10<sup>14</sup> to 10<sup>15</sup> e/cm<sup>2</sup> in a
high voltage transmission electron microscope. The germanium fraction of
the Si<sub>1-x</sub>Ge<sub>x</sub> epitaxial layer used for the diodes
in this study is x=0.12 and 0.16. The degradation of the diode
performance and the presence of deep levels are investigated as a
function of electron fluence and germanium content. The degradation of
the x=0.12 diodes is more remarkable than that of the x=0.16 diodes. In
order to examine the recovery process, isochronal thermal anneals are
performed in the temperature range between 100 and 350°C. From the
annealing behaviour, it is pointed out that the electron capture levels,
which are related with interstitial boron, are mainly responsible for
the increase of reverse and forward current
The use of nonionizing energy loss (NIEL) in predicting the effect
of gamma, electron, and proton irradiations on Si, GaAs, and InP devices
is discussed. The NIEL for electrons and protons has been calculated
from the displacement threshold to 200 MeV. Convoluting the electron
NIEL with the slowed down Compton secondary electron spectrum gives an
effective NIEL for CO<sup>60</sup> gammas, enabling gamma-induced
displacement damage to be correlated with particle results. The fluences
of 1 MeV electrons equivalent to irradiation with 1 Mrad(Si) for Si,
GaAs, and InP are given. Analytic proton NIEL calculations and results
derived from the Monte Carlo TRIM agree exactly, as long as straggling
is not significant. The NIEL calculations are compared with experimental
proton and electron damage coefficients using solar cells as examples. A
linear relationship is found between the NIEL and proton damage
coefficients for Si, GaAs, and InP devices. For electrons, there appears
to be a linear dependence for n-Si and n-GaAs, but for p-Si there is a
quadratic relationship which decreases the damage coefficient at 1 MeV
by a factor of ~10 below the value for n-Si
The effects of irradiating Ga<sub>0.47</sub>In<sub>0.53</sub>As
solar cells and p-i-n photodiodes with 1-MeV electrons were measured
using deep level transient spectroscopy (DLTS) and both dark and
illuminated (1 sun, air mass zero (AM0)) I - V
measurements. Fits of the dark I - V data to the
two-term diode equation before irradiation were satisfactory, yielding
an estimated bandgap energy of 0.79 eV. The DLTS detected two
radiation-induced defect levels, one shallow (0.10 eV) and one near
mid-gap (0.29 eV). Temperature coefficients of the Ga<sub>0.47</sub>In
<sub>0.53</sub>As photovoltaic parameters follow the same general
behavior as for other solar cell materials (e.g., Si and GaAs). However,
a sharp decrease in the short circuit current is observed above ≈375
K. This temperature is reduced by irradiation. Isochronal thermal
annealing induced recovery in the photovoltaic parameters at ≈400 K,
coinciding with an annealing stage of the near mid-gap defect
level
Capacitance transient spectroscopy has been used to study defect states in 1-MeV electron irradiated liquid phase epitaxial InGaAsP. No states were found in the unirradiated material. Irradiation resulted in one electron trap with an electron emission activation energy of 0.38 eV and two hole traps with hole emission activations of 0.29 and 0.46 eV. Annealing behavior and the broad shape of the deep level transient spectroscopy peaks suggest that defect properties are affected by local ordering and stoichiometry in the material. All three defects recover significantly at temperatures
A method is outlined for determining the total number of photons at each energy for a given irradiation from a betatron, assuming the bremsstrahlung photon distribution to be represented by an equation of Schiff and the response of an r-meter to be proportional to the absorption cross section for photons in the wall material. The resulting activities produced by gamma-neutron reactions in Cu63, Cu65, Sb121, Sb123, and Ta181 have been measured as functions of the maximum photon energy of the betatron. In each case the activity was normalized to saturation per gram for 100 roentgens of radiation. A method is also outlined whereby these activation curves may be analyzed to give the photo-neutron cross section as a function of energy. The cross section for Cu63 obtained by this method has its maximum at 17.5 Mev with a resonance half-width of 6 Mev and an integrated area of 0.7 Mev-barn. Maxima for the other nuclides are at somewhat lower energies and have essentially the same half-width.
A detailed analysis of the reverse characteristics of In0.53Ga0.47As pin-photodiodes at various temperatures reveals, besides generation, diffusion and band-to-band tunneling of carriers, an additional contribution to the dark current due to tunneling through an energy barrier of 0.16± 0.02 eV. In deep-level transient spectroscopy measurements a thermal activation energy of 0.57± 0.01 eV, equal to the gap energy minus the tunneling barrier, has been found. From these two measurements it can be concluded that thermal activation of deep traps and subsequent tunneling of carriers into band states leads to the additional dark current component.
We report on deep levels in In 0.53 Ga 0.47 As/InP heterostructure avalanche photodiodes grown by liquid‐phase epitaxy. Two electron levels have been identified and studied using both admittance spectroscopy and a static capacitance‐voltage technique. One level, found only in the InP layer, is acceptor‐like with an activation energy of ϵ tA = 0.20±0.02 eV and has a density in the bulk of the InP layer of N tA ≊ 10<sup>15</sup> cm<sup>-3</sup>. The density of the trap increases sharply at the In 0.53 Ga 0.47 As/InP heterointerface to a value nearly ten times the background carrier concentration in this region. Filling of this trap at low temperatures reduces the conduction band discontinuity at the heterointerface from Δϵ c = 0.19 to 0.03 eV due to repulsion of the bands. The second trap, which is characteristic only of the In 0.53 Ga 0.47 As, has an activation energy of ϵ tB = 0.16±0.01 eV, and a density of between 3×10<sup>13</sup> and 8×10<sup>13</sup> cm<sup>-3</sup>.
Because of the low‐intrinsic and radiation‐induced attenuation losses in glass fibers in the wavelength range 1.0–1.3 μm, emitters and detectors operating in this range are of practical importance for radiation‐environment applications. We have studied the effects of both γ and neutron irradiation on the properties of InGaAs LED’s emitting at 1.06 μm and Si photodiode detectors optimized for this wavelength. While the preirradiation light output of the InGaAs LED’s is low relative to many GaAs LED’s, the InGaAs devices exhibit less sensitivity to radiation than the most radiation‐hardened GaAs LED’s. No significant neutron‐induced light‐output degradation is observed below 1×10<sup>13</sup> n/cm<sup>2</sup>, while 2×10<sup>7</sup> Co‐60 rads are required before any γ‐induced degradation is observed. In addition, a significant portion of the γ‐induced light‐output degradation can be recovered by applying forward‐bias currents of the order of 50 mA in magnitude. Although γ irradiation up to 2×10<sup>8</sup> rads has essentially no effect on the photodiodes, neutron fluences above 2×10<sup>14</sup> n/cm<sup>2</sup> cause a reduction in responsivity. Analysis of the neutron‐induced increases in the photodiode leakage current with the guard ring attached reveals a lifetime‐damage constant product of 4×10<sup>-12</sup> cm<sup>2</sup>/n. Laboratory isolators made up of these emitters and detectors have typical preirradiation current‐transfer ratios of 5×10<sup>-4</sup> which decrease by a factor of 10 after an irradiation of 1.5×10<sup>14</sup> n/cm<sup>2</sup>.
Modulation doped Ga 0.47 In 0.53 As‐Al 0.48 In 0.52 As single‐period heterostructures have been prepared by molecular beam epitaxy (MBE). Electron mobilities as high as 8915 cm<sup>2</sup>/V s at 300 K, 60 120 cm<sup>2</sup>/V s at 77 K, and 90 420 cm<sup>2</sup>/V s at 10 K were obtained with an average electron concentration of ∼10<sup>17</sup> cm<sup>-3</sup>. These results represent a mobility enhancement over uniformly doped Ga 0.47 In 0.53 As with the same carrier concentration by about a factor of 6 at 77 K and by a factor of 2 at 300 K. Single‐period modulation doped heterostructures have shown enhanced mobility in spite of the relative positions of the Si‐doped Al 0.48 In 0.52 As layer and the undoped Ga 0.47 In 0.53 As layer in contrast to the case of GaAs/Al x Ga 1-x As system where mobility enhancement has only been observed for MBE grown Al x Ga 1-x As on top of the undoped GaAs layer.
The growth of higher purity InGaAs by the addition of O2 has been investigated in hydride VPE. A 77 K mobility as high as 35000 cm2 V−1 s−1 (8400 cm2 V−1 s−1 at 300 K) with a carrier concentration of 1.8×1015 cm−3 (2.4×1015 cm−3 at 300 K) was obtained with the addition of 12 ppm O2. It was also found that InGaAs layers grown on (100)−2° (toward (110)) oriented InP substrates had lower carrier concentration and poorer mobility, compared to those grown on (100) substrates.
The degradation under 5.5-MeV proton irradiation of two classes of
quantum-well-based fiber-optic light sources was evaluated for satellite
applications. The first was an InGaAs/GaAs strained-layer quantum-well
(QW) laser, and the second was a broadband light-emitting diode (LED)
based on dual asymmetric quantum wells in the InGaAs/GaAs/AlGaAs system.
The QW LEDs were more tolerant of proton irradiation (-3 dB power at
~3×10<sup>13</sup> protons/cm<sup>2</sup>) than the QW lasers (-3
dB power at ~3×10<sup>12</sup> protons/cm<sup>2</sup>). The LEDs
were operated far into gain saturation with a high-loss cavity
structure, while the lasers were operated in a region where gain was
more sensitive to current density. Therefore, atomic
displacement-related recombination sites had a greater detrimental
effect upon the lasers than the LEDs. The lasers held constant slope
efficiency, and current thresholds increased linearly with proton
fluence, while both LED power and slope efficiency decreased with proton
fluence. The determined damage factors for both devices were found to
fall within values predicted from a universal damage relation previously
reported by G.P. Summers et al. (1988)
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