Cathodoluminescence and isochronal annealing investigations of edge-emission in ZnTe

Investigation of the liquid helium temperature cathodoluminescence edge-emission of undoped ZnTe has shown that two bands at 545.8 and 547.3 nm result respectively from free-to-bound and donor-acceptor pair recombination at a common acceptor level with a hole binding energy of 124 meV. From observations of the changes that occur in the edge-emission spectrum after isochronal (30 min) annealing treatments in vacuum in the temperature range 50–500°C it is suggested either that the acceptor defect is mobile and can move out of sites at which it behaves as an acceptor to sites at which it behaves as a donor or, during annealing complexing occurs which changes the nature of the centre and effectively removes it.     

Cathodoluminescence study of extended defects in hydrothermal ZnO crystals

Understanding the luminescence of ZnO is very important for some applications. In spite of the many studies carried out, there are still some points concerning the origin of some of the luminescence emissions in ZnO crystals that require additional study; in particular, the role of extended defects remains to be a matter of controversy. We present here a cathodoluminescence analysis of the defects generated by Vickers indentation in hydrothermal HTT crystals. Special emphasis was paid to the luminescence band peaking around 3.3 eV. The origin of this band is a matter of controversy, since it has been related to different causes, extended defects being one of the candidates for this emission. The CL images were acquired around crystal defects. It is observed that the 3.3 eV emission is enhanced around the crystal defects; though it is also observed, but weaker, out of the defect regions, which suggests that there exist two luminescence emissions peaking very close to 3.3 eV. The two emissions, one related to structural defects and the other to the LO phonon replica of the free excitonic band, appear very close each other and their relative intensity should determine the shape of the spectrum.     

RIE-induced damage and contamination in silicon

Abstract

Reactive ion etching always causes a dynamic radiation effect to crystalline silicon, beacause of an energetic particle bombardment. RIE induced radiation effects are mostly confined to the near surface within a projected range of impinging ions, but point defects, which are highly mobile at room temperatures, can migrate further into the bulk before a damaged surface layer is etched away. Competition between etch rates and damage rates ultimately determines a degree of the RIE damage residue: the slower the etch rate, the heavier the damage may be accumulated at the near surface, eventually leading to amorphization of the surface region. Also, a removal of the surface layer due to etching or sputtering enhances a chemical reaction between a bare surface and incoming radicals. This easily forms a foreign material on the surface which gives rise to a serious contamination problem. A post-cleaning at a low temperature is highly desirable whenever the surface of active devices must be exposed to reactive plasmas.     

Light-induced defects in plasma-hydrogenated InP: Zn

PhotoLuminescence (PL) measurements are used to investigate the effects of a H₂ plasma treatment in heavily doped p-type InP: Zn. Beside the large decrease in free hole concentration in the hydrogenated samples, a new Broad Luminescence Band (BLB) centered at about 1.32 eV appears upon laser irradiation during PL experiments above 50 K, and saturates for large values of the fight intensities. It is inferred that the plasma treatment produces some kind of non-radiative defects which can then rearrange into new BLB centers under illumination provided it is applied above a threshold temperature (50K). This mechanism is interpreted in terms of Recombination-Enhanced Defect Reaction (REDR) involving the two kinds of photogenerated carriers and appears to be low thermally assisted. The BLB is associated with the radiative emission at a phosphorus vacancy (V_p) close to a Zn acceptor (V _p ⁺ Zn _In ^– ). It is believed that the formation of BLB centers originates from V_p-related defects initially present in the freshly plasma-treated InP sample. The mechanisms involved in the Light-Induced Creation (LIC) of BLB centers are discussed.     

Lattice coupling strength of electron-induced-irradiated defects in InP

Optical properties of some Electron-Induced-Irradiated defects in InP, hole traps H₇, H₅, H₄ and electron trap E₁₁, are investigated by means of Deep-Level-Optical-Spectroscopy.Both majority and minority photoionisation cross-sections measurements of E₁₁ and H₅ are performed, together with direct measurements of the hole capture cross section of H₅. In case of levels H₇ and H₄ the only majority photoionisation cross section could be obtained.Interpretation is made on the basis of one dimensional configuration coordinate diagrams. From these it is concluded that levels H₄ and E₁₁ are weakly relaxed while levels H₅ and H₇ are strongly coupled to the lattice. This is a new indication that EII defects in InP can be at least classified into two groups, owing to their microscopic origin and to their physical properties.     

InP中深能级缺陷的产生与抑制现象

研究了原生和高温退火处理后非掺n型和半绝缘InP单晶材料中产生的缺陷.在磷气氛下退火后，n型和半绝缘InP单晶中均明显产生相当数量的深能级缺陷，而在磷化铁气氛下退火后，InP的缺陷数量明显减少.在退火过程中缺陷的产生与磷和铁的内扩散有直接关系.向内扩散的磷原子和铁原子占据晶格中铟位后，分别产生反位缺陷和铁深受主.实验结果表明，铁通过扩散充分占据了铟位，抑制了铟空位、磷反位等缺陷的形成，而磷气氛下退火后产生的缺陷有铟空位、磷反位等.对InP中的缺陷属性进行了分析. 关键词： 磷化铟 退火 缺陷     

Optical properties of electron irradiation induced defects in InP

The optical properties of deep hole traps H₄ and H₅ in p type and of the deep electron trap E₁₁ in n type InP, introduced by electron irradiation, have been studied using deep level optical spectroscopy. Comparison of the optical threshold with the thermal activation energy of H₅ level shows that it is highly relaxed with a Frank-Condon shift d_Fc = 0.45 eV. The electron level E₁₁ is weakly relaxed and its optical cross section σ ⁰ is well accounted for by transitions to the Γ_6c minimum. The optical absorption σ_p⁰ associated to level H₄ shows two successive onsets at hν = 0.5 and hν = 1.2 eV which can be attributed to hole transitions to the Γ_7–8 and to the L_4–5 valence band extrema, respectively. The deduced Frank-Condon shift, d_Fc = 0.23 eV, agrees with the measured difference of 40 meV between its apparent activation energy E_a and its thermal activation energy E_T.     

高温退火后非掺杂磷化铟材料的电子辐照缺陷

对不同气氛下高温退火非掺杂磷化铟(InP)材料的电子辐照缺陷进行了研究. 除铁受主外，磷化铁(FeP₂)气氛下退火后的InP中辐照前没有深能级缺陷，而辐照后样品的热激电流谱(TSC)中出现了5个较为明显的缺陷峰，对应的激活能分别为0.23 eV, 0.26 eV, 0.31 eV, 0.37 eV和0.46 eV. 磷(P)气氛下退火后InP中的热生缺陷较多，电子辐照后形成的缺陷具有复合体特征. 与辐照前相比，辐照后样品的载流子浓度和迁移率产生显著变化. 在同样的条件下，经FeP₂ 气氛下高温退火后的InP样品的辐照缺陷恢复速度较快. 根据这些现象分析了缺陷的属性、快速恢复机理和缺陷对材料电学性质的影响. 关键词： 磷化铟 电子辐照 缺陷     

深能级缺陷对半绝缘InP材料电学补偿的影响

对铁掺杂和高温退火非掺杂磷化铟制备的两种半绝缘材料的电学补偿和深能级缺陷进行了分析和比较.根据热激电流谱(TSC)测得的深能级缺陷结果，分析了这两种半绝缘InP材料中深能级缺陷对电学补偿的影响.在掺铁半绝缘InP材料中，由于存在高浓度的深能级缺陷参与电学补偿，降低了材料的补偿度和电学性能.相比之下，利用磷化铁气氛下高温退火非掺InP获得的半绝缘材料的深能级缺陷浓度很低，通过扩散掺入晶格的铁成为唯一的深受主补偿中心钉扎费米能级，材料表现出优异的电学性质.在此基础上给出了一个更为广泛的半绝缘InP材料的电学补偿模型.     

Further investigations of tunneling recombination processes in random distributions of defects

The shape of infrared stimulated luminescence signals (IRSL) from feldspars has been the subject of numerous studies in the field of luminescence dating. Specifically linearly modulated IRSL signals (LM-IRSL) are commonly assumed to consist of several first order components corresponding to distinct optical stimulation cross sections. This paper models the shape of LM-IRSL signals using a recently proposed kinetic model, which describes localized electronic recombination in donor–acceptor pairs of luminescent materials. Within this model, recombination is assumed to take place via the excited state of the donor, and nearest-neighbor recombinations take place within a random distribution of centers. The model has been used previously successfully to describe both thermally and optically stimulated luminescence (TL, OSL). This paper shows that it is possible to obtain approximate solutions for the distribution of donors in the ground state as a function of two variables, time and the distance between donors and acceptors. Approximate expressions are derived for several possible modes of optical and thermal stimulation, namely TL, OSL, linearly modulated OSL (LM-OSL), LM-IRSL and isothermal TL (ITL). Numerical integration of these expressions over the distance variable yields the distribution of remaining donors at any time t during these experimental situations. Examples are given for the derived distributions of donors in each experimental case, and similarities and differences are pointed out. The paper also demonstrates how LM-IRSL signals in feldspars can be analyzed using the model, and what physical information can be extracted from such experimental data. The equations developed in this paper are tested by fitting successfully a series of experimental LM-IRSL data for Na- and K-feldspar samples available in the literature. Finally, it is shown that the equations derived in this paper are a direct generalization of an equation previously derived for the case of ground state tunneling.     

Mössbauer study of defects created by low-fluence In+ implantations in InP

The temperature and fluence dependence of defect interactions in damage cascades in n-type InP has been investigated with ion-implanted radioactive¹¹⁹In (T _1.2=2.1 min) probe atoms. The hyperfine interactions for the¹¹⁹Sn Mössbauer daughter atoms in the resulting defect structures have been determined. An annealing model based on the temperature dependent mobility of lattice defects and their interactions in three observed annealing stages is proposed.     

Characterization of the bulk defects in InP crystal with a high-resolution triple-crystal X-ray diffractometer

Intensity distributions for various reflections from InP single crystal were measured with a triple-crystal X-ray diffractometer. The measured intensity patterns were compared with those calculated for a perfect crystal. This comparison showed a good agreement for the Bragg-case diffraction, while a broadening of the measured intensity profiles was observed for the Laue-case diffraction. This broadening results from the presence of microdefects in the bulk of the material. The critical radius of the microdefects was estimated to be in the range of 1 to 2 m from the power law of scattering for the Laue reflection curves. The microdefects were found to be of interstitial type and the computer simulations suggest that they are formed by aggregation of dislocation loops consistent with {111} 110 model.     

Cathodoluminescence of oxyfluoride glass-ceramics

Tb, Ce, Eu activated oxyfluoride glass-ceramics with the composition SiO₂ · Al₂O₃ · Li₂O · LaF₃ have been studied by cathodoluminescence (CL). We compared CL intensities and decay times of the Tb, Ce, Eu activated glass-ceramic samples and observed that the Tb activated sample has the most intense luminescence, but the Ce activated sample has the shortest decay times. Induced optical absorption and thermostimulated luminescence have been observed after X-ray irradiation of samples.     

Cathodoluminescence in ion-implanted BeO crystals

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 51, No. 2, pp. 218–224, August, 1989.