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1.
Boussairi Bouzazi Hidetoshi SuzukiNobuaki Kojima Yoshio OhshitaMasafumi Yamaguchi 《Physica B: Condensed Matter》2011,406(5):1070-1075
A nitrogen-related electron trap (E1), located approximately 0.33 eV from the conduction band minimum of GaAsN grown by chemical beam epitaxy, was confirmed by investigating the dependence of its density with N concentration. This level exhibits a high capture cross section compared with that of native defects in GaAs. Its density increases significantly with N concentration, persists following post-thermal annealing, and was found to be quasi-uniformly distributed. These results indicate that E1 is a stable defect that is formed during growth to compensate for the tensile strain caused by N. Furthermore, E1 was confirmed to act as a recombination center by comparing its activation energy with that of the recombination current in the depletion region of the alloy. However, this technique cannot characterize the electron−hole (e-h) recombination process. For that, double carrier pulse deep level transient spectroscopy is used to confirm the non-radiative e-h recombination process through E1, to estimate the capture cross section of holes, and to evaluate the energy of multi-phonon emission. Furthermore, a configuration coordinate diagram is modeled based on the physical parameters of E1. 相似文献
2.
Hoon Young Cho Eun Kyu Kim Suk-Ki Min Sung Ho Choh 《Applied Physics A: Materials Science & Processing》1989,48(4):359-363
We studied the midgap levels by using isothermal capacitance transient spectroscopy (ICTS) in Hb-GaAs which had been processed by rapid thermal annealing (RTA). As the annealing time at 850 °C increased, the EL2 trap (E
c–0.81 eV) was transformed to the EX2 trap (E
c–0.73 eV) and eventually to the EX1 trap (E
c–0.87 eV). The diffusivity of the EL2 trap obtained from the experimental result of the heat treatment was about 1.02·10–8cm2/s at 850 °C. This result indicate that the EL2 trap contains an interstitial arsenic atom. The result of the transformation to the EX1 and EX2 traps suggests that, when the EL2 trap is VAsASiVGaAsGa, the EX2 trap may be VAsVGaAsGa, which Asi is diffused out during a thermal annealing. 相似文献
3.
Summary This work reports the electronic structure of GaInAsSb quaternary alloy by recursion method. A five-orbital sp3s* per atom model was used in the tight-binding representation of the Hamiltonian. The local density of states (LDOS), integrated
density of states (IDOS) and structural energy (ST.E) were calculated for Ga, In, As and Sb sites in Ga0.5 In0.5 As0.5 Sb0.5 and GaInAsSb lattice matched to GaAs and the same alloy lattice matched to GaSb. There are 216 atoms in our cluster arranged
in a zincblend structure. The results are in good agreement with available information about the alloy. 相似文献
4.
Using first-principles calculations we investigate the mutual passivation of shallow donor Si and isovalent N in dilute GaAsN alloys. Instead of the recently proposed pairing of Si and N on adjacent substitutional sites (Si(Ga)-N(As)) [K. M. Yu et al., Nat. Mater. 1, 185 (2002); J. Li et al., Phys. Rev. Lett. 96, 035505 (2006)] we find that N changes the behavior of Si in dilute nitride alloys in a more dramatic way. N and Si combine into a deep-acceptor split interstitial, where Si and N share an As site [(Si-N) (As)], with a significantly lower formation energy than that of the Si(Ga)-N(As) pair in n-type GaAs and dilute GaAsN alloys. The formation of (Si-N)(As) explains the GaAs band-gap recovery and the appearance of a photoluminescence peak at approximately 0.8 eV. This model can also be extended to Ge-doped GaAsN alloys, and correctly predicts the absence of mutual passivation in the case of column-VI dopants. 相似文献
5.
Deep level transient spectroscopy investigation of deep levels in CdS/CdTe thin film solar cells with Te:Cu back contact
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Deep levels in Cds/CdTe thin film solar cells have a
potent influence on the electrical property of these devices. As an
essential layer in the solar cell device structure, back contact is
believed to induce some deep defects in the CdTe thin film. With the
help of deep level transient spectroscopy (DLTS), we study the deep
levels in CdS/CdTe thin film solar cells with Te:Cu back contact.
One hole trap and one electron trap are observed. The hole trap H1,
localized at Ev+0.128~eV, originates from the vacancy of Cd
(VCd. The electron trap E1, found at Ec-0.178~eV,
is considered to be correlated with the interstitial Cui=
in CdTe. 相似文献
6.
《Journal of magnetism and magnetic materials》2002,238(2-3):252-257
In the diluted magnetic semiconductor (Ga,Mn)As the excess of As incorporated as As antisites (AsGa) is responsible for the hole compensation. The AsGa defect can be transformed into a As interstitial–Ga vacancy pair (Asi–VGa) upon illumination. In this paper we study the effects of such a transition on the ferromagnetism of (Ga,Mn)As using density functional theory within the local spin density approximation. We find that the ferromagnetic order in (Ga,Mn)As is strongly enhanced if AsGa are transformed into Asi–VGa pairs, since the hole compensation is reduced. This suggests a valuable way to tune the carrier concentration and hence the Tc in (Ga,Mn)As, without changing the Mn concentration nor the microscopic configuration of the Mn ions. 相似文献
7.
Space-charge-limited-trap-limited hole currents in anthracene crystals are interpreted in terms of a trap distribution which starts at a discrete trap level at 0·6–0·8 eV and in which the trap density falls off exponentially with energy relative to this level. It is suggested that exponential hole trap distributions are produced by physical perturbations of the crystal lattice introduced by the same impurities which give rise to the discrete hole trap level at 0·6–0·8 eV (revealed by thermally stimulated current studies). The results indicate that a perturbed molecule is introduced for every 10,000 impurity molecules and the total number of perturbed molecules is constant at 1017 m?3 for melt-grown and vapor-grown crystals. The parameter kTc varies from crystal to crystal, indicating that the relative contributions of highly perturbed and slightly perturbed molecules is influenced by crystal growth conditions. 相似文献
8.
9.
L. Guo H.-S. Wu 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,42(2):259-267
Geometries, electronic states and electron affinities of AlmAsn and AlmAs n (m+n=2–5) clusters have been examined using
four hybrid and pure density functional theory (DFT) methods. Structural
optimization and frequency analyses are performed using a 6-311+G(2df)
one-particle basis set. The geometries are fully optimized with each DFT
method independently. The three types of energy separations reported in this
work are the adiabatic electron affinity (EAad), the vertical electron
affinity (EAvert), and the vertical detachment energy (VDE). The
calculation results show that the singlet structures have higher symmetry
than that of doublet structures. The best functional for predicting
molecular structures was found to be BLYP, while other functionals generally
underestimated bond lengths. The largest adiabatic electron affinity,
vertical electron affinity and vertical detachment energy, obtained at the
6-311+G(2df)/BP86 level of theory, are 2.20, 2.04 and 2.27 eV (AlAs), 2.13,
1.94 and 2.38 eV (AlAs2), 2.44, 2.39 and 2.47 eV (Al2As), 2.09,
1.80 and 2.53 eV (Al2As2), 2.01, 1.57 and 2.36 eV (AlAs3),
2.32, 2.11 and 2.55 eV (Al2As3), 2.40, 1.45 and 3.26 eV
(AlAs4), 1.94, 1.90 and 2.07 eV (Al4As), respectively. However, the
BHLYP method gives the largest values for EAad and EAvert of
Al3As and EAad of Al3As2, respectively. For the
vibrational frequencies of the AlnAsm series, the B3LYP method
produces good predictions with the average error only about 10 cm-1 from available experimental and theoretical values. The other three functionals overestimate or underestimate the vibrational
frequencies, with the worst predictions given by the BHLYP method. 相似文献
10.
K. A. Nasyrov S. S. Shaĭmeev V. A. Gritsenko J. H. Han C. W. Kim J. -W. Lee 《Journal of Experimental and Theoretical Physics》2006,102(5):810-820
The kinetics of electron and hole accumulation in metal-oxide-nitride-oxide-semiconductor structures is studied. Experimental data are compared with a theoretical model that takes into account tunnel injection, electron and hole capture by traps in amorphous silicon nitride SiNx, and trap ionization. Agreement between experimental and calculated data is obtained for the bandgap width E g = 8.0 eV of amorphous SiO2, which corresponds to the barrier for holes Φh = 3.8 eV at the Si/SiO2 interface. The tunneling effective masses for holes in SiO2 and SiNx are estimated at m h * ≈ (0.4–0.5)m 0. The parameters of electron and hole traps in SiNx are determined within the phonon-coupled trap model: the optical energy W opt = 2.6 eV and the thermal energy W T = 1.3 eV. 相似文献
11.
T. Ishida K. Maeda S. Takeuchi 《Applied Physics A: Materials Science & Processing》1980,21(3):257-261
Deformation-produced deep levels, both of electron and hole traps, have been studied using deep level transient capacitance
spectroscopy (DLTS) for an undopedn-type GaAs (HB grown) compressed at 440°C. Concentrations of two grown-in electron trap levels (E
c
−0.65eV andE
c
−0.74eV) and one grown-in hole trap level (E
v
+∼0.4eV) increase with plastic deformation, while that of a grown-in electron trap level (E
c
−∼0.3eV) decreases in an early stage of deformation. While no new peak appeared in the electron trap DLTS spectrum after plastic
deformation, in the hole trap DLTS spectrum a broad spectrum, seemingly composed of many peaks, newly appeared in a middle
temperature range, which may be attributed to electronic energy levels of dislocations with various characters. 相似文献
12.
We report the application of Deep Level Transient Spectroscopy (DLTS) in Hg1-xCdxTe, demonstrating for the first time the utilization of DLTS techniques in a narrow band-gap semiconductor, Eg < 0.40 eV. DLTS measurements performed on an n+-p diode with Eg (x=0.21, T=30 K) =0.096 eV have identified an electron trap with an energy of Ev + 0.043 eV and a hole trap at Ev + 0.035 eV. Measurements of trap densities, capture cross sections, and the close proximity of the electron and hole trap locations within the band-gap suggest that DLTS may be observing both the electron and hole capture at a single Shockley-Read recombination center. The trapping parameters measured by DLTS predict minority carrier lifetime versus temperature data to be comparable with the experimentally measured values. 相似文献
13.
T. Wosiński 《Applied Physics A: Materials Science & Processing》1985,36(4):213-216
By photocapacitance technique, applied to n-type LEC-grown GaAs, two energy levels:E
v
+0.45 eV andE
c
–0.75 eV are identified, for the first time, as being associated with the EL2 trap. As follows from the analysis of photo-EPR results on highly resistive GaAs crystals, the same energy levels can be attributed to the arsenic antisite defect, AsGA. In view of these findings, it is argued that the occupied EL2 level corresponds to the neutral charge state of AsGa defect. 相似文献
14.
《Journal of Physics and Chemistry of Solids》2007,68(5-6):953-957
Chalcogenide thin films could be prepared by many experimental methods resulting in some differences in structure and physicochemical properties of prepared films. In this work, the As33S67 amorphous films were prepared by three different preparation techniques: vacuum thermal evaporation (TE), pulsed laser deposition (PLD) and spin-coating (SC). A silver film was deposited on the top of the As33S67 films and photodoped.The X-ray diffraction analysis showed significant differences in arrangement between bulk glass and thin films and also among films themselves. The Raman spectroscopy showed that the Raman spectra of PLD film and bulk glass are almost similar. On the other hand, TE films contain higher amount of homopolar bonds As–As and S–S. The value of refractive index of As33S67 bulk glass was 2.31. All prepared films have lower index of refraction contrary to bulk glass, i.e. TE∼2.27, PLD∼2.20 and SC∼1.90. The increase of refractive index with silver concentration is shown either. The optical bandgap of undoped As–S prepared films was different: TE∼2.42 eV, PLD∼2.45 eV and SC∼2.54 eV. 相似文献
15.
E.P. Valcheva 《Applied Physics A: Materials Science & Processing》1997,65(1):39-42
x Ga1-xAs heterojunctions grown by liquid-phase epitaxy. Interface states with hiqh concentration, Nt=3×1011 cm-2 and energy level Ec-Et=0.14 eV distributed in a box 150 Å wide at the heterointerface and acting as electron traps are observed. The possible origin
could be the isolated arsenic vacancy VAs in n-GaAs.
Received: 25 April 1996/Accepted: 22 January 1997 相似文献
16.
J. Teubert P.J. Klar W. Heimbrodt K.Volz W. Stolz A. Polimeni M. Capizzi 《Physica E: Low-dimensional Systems and Nanostructures》2006,32(1-2):218
(Ga,In)(N,As) lattice matched to GaAs with a band gap of 1 eV is employed as active material in high-efficiency III–V solar cells. Te-doped Ga0.934In0.066N0.023As0.977 layers were grown by metal-organic vapor-phase epitaxy on (1 0 0) GaAs. The samples were highly doped n-type with carrier concentrations ranging from about 1017–1019 cm−3. Pieces of the samples were hydrogenated with H-doses of 1018 ion/cm2. The optical and electrical properties of the samples before and after hydrogenation were studied by low-temperature photoluminescence and magnetotransport. In undoped samples hydrogen is known to form N–H complexes which strongly reduce the local perturbation of the lattice due to nitrogen and thus reverse the N-induced global changes of the band structure. Combined analysis of photoluminescence and transport measurements on Te-doped samples, however, indicates a competition between N–H formation and passivation of the Te donor favoring the latter. Hardly any band structure changes due to hydrogenation are observed in these Te-doped samples, instead a strong reduction of the free-carrier concentration is observed after hydrogenation. 相似文献
17.
《Solid State Communications》1987,61(4):241-244
We report photoluminescence spectra of defects in irradiated silicon which are stable below room temperature. No-phonon lines (STI)0 at ≈ 856 meV, ST2 at ≈ 1115 meV, and ST3 at ≈ 1126 meV are observed along with a broad emission band extending from 0.7 to 1 eV. The ST1 defect studied in detail is a deep hole trap at ≈ Ev + 0.25 eV, which in addition can bind an electron loosely. Piezospectroscopy shows that the defect is essentially <100 > axial symmetric with slight distortion to C1h. The absence of Zeeman splittings confirms the deep hole binding in an axially symmetric potential. The independence of dopants, the annealing behaviour, and comparison to EPR and IR active defects suggest a correlation of the ST1 defect with interstitial carbon. 相似文献
18.
19.
用DLTS和单次脉冲瞬态电容技术研究了液相外延生长的双异质结AlxGa1-xAs/GaAs发光管,掺Si的n-Al0.05Ga0.95As有源层中的深能级。着重分析了一个与氧有关的电子陷阱,其发射激活能为EC-ED=0.29eV。我们发现该电子陷阱随正向注入脉冲宽度tp的增加DLTS峰向低温移动,即在确定的温度下发射率随tp的增加而增加。用DLTS首次测得该能级的俘获瞬态谱,发现俘获峰随反向撤空脉冲宽度tR的增加向低温端移动,即在确定的温度下俘获率随tR的增加而增加,并且俘获激活能从△Eσ=0.28eV变化到0.26eV,用位形坐标图讨论了引起变化的原因。 相似文献
20.
H. Künzel A. Fischer J. Knecht K. Ploog 《Applied Physics A: Materials Science & Processing》1983,32(2):69-78
The persistent photoconductivity effect in Si-dopedn-Al x Ga1?x As layers grown by molecular beam epitaxy on (100)GaAs substrates has been investigated by detailed Halleffect and capacitance measurements at 10–300 K. In the alloy composition range 0.25<x <0.40 the electrical properties ofn-Al x Ga1?x As are governed by a deep electron trap having an emission barrier of 0.34–0.40 eV (depending on the doping concentration), as determined by admittance measurements. The concentration of deep electron traps, deduced from low-temperature capacitance measurements, is found to coincide with the amount of persistent photoconductivity observed in the material. Consequently, the earlier proposed population of two-dimensional subbands at the Al x Ga1?x As/GaAs-substrate hetero-interface, i.e. charge separation bymacroscopic barriers, can not account for the measured high overall number of persistent photoexcited carriers. Instead, the vanishing small capture rates of photoexcited electrons result frommicroscopic capture barriers. The dominant deep electron trap, which we attribute to deep donor-type (DX) centers, is found to be homogeneously distributed throughout the Al x Ga1?x As layer depth. From our Hall effect measurements a trap depth of 0.05–0.12 eV (depending on the doping concentration) below the conduction band is derived. The capture barrier is thus in the order of 0.30 eV. This value is in excellent agreement with data obtained from liquid phase epitaxially grown Si-dopedn-Al x Ga1?x As. 相似文献