The studies of Ge quantum dots on strained Si0.7Ge0.3 layer by photoluminescence and deep level transient spectroscopy

Systematic studies of Ge quantum dots (QDs) grown on strained Si_0.3Ge_0.7 layer have been carried out by photoluminescence (PL) and deep level transient spectroscopy (DLTS). In PL measurements, two peaks around 0.7 eV are distinguished, which are assigned to two types of QDs observed by atomic force microscopy (AFM). Large blueshifts of the PL peaks from small QDs with the increase of excitation power are observed and attributed to the band bending effects typical for type-II band alignment. From DLTS measurements, the energy levels of holes in both types of QDs are derived, which shift with the change of the number of holes in QDs due to their charge energy. By comparing results from PL and DLTS measurements, further understanding of band alignment with the increase of the number of excitons in QDs is deduced.     

Electrical and deep levels characteristics of ZnO/Si heterostructure by MOCVD deposition

ZnO films have been prepared on p-type Si substrates by metal-organic chemical vapour deposition （MOCVD） at different total gas flow rates. The current versus voltage and temperature （I - V - T） characteristics, the deep-level transient spectroscopy （DLTS） and the photoluminescence （PL） spectra of the samples were measured. DLTS shows two deep-level centres of E1 （Ec-0.13±0.02eV） and E2 （Ec-0.43±0.05eV） in sample 1202a, which has a ZnO/p-Si heterostructure. A deep level at Ec-0.13±0.01 eV was also obtained from the I -T characteristics. It was considered to be the same as E1 obtained from DLTS measurement. The emission related to this deep level center was detected by PL spectra. In addition, the energy location and the relative trap density of E1 was varied when the total gas flow rate was changed.     

少子陷阱特性和铍硅共注半绝缘GaAs空穴陷阱

用深能级瞬态谱（ＤＬＴＳ）技术测量了高温退火的Ｂｅ和Ｓｉ共注入的ＬＥＣ半绝缘ＧａＡｓ（无掺杂）。在多子脉冲作用下的Ａｌ／Ｂｅ－Ｓｉ共注ＬＥＣＳＩＧａＡｓ肖特基势垒中，观测到Ｅ₀₁（０．２９８），Ｅ₀₂（０．３４１），Ｅ₀₃（０．５５５）和Ｅ₀₄（０．８２１）等四个电子陷阱以及两个主要的少子（空穴）陷阱Ｈ＇₀₃（０．５４）和Ｈ″₀₃（０．５７）。两少子陷阱的ＤＬＴＳ信号具有若干特点，比如它们的ＤＬＴＳ·峰难于通过增宽脉冲达到最大高度；以及峰的高度强烈地依赖于温度等。这些现象可以用少子陷阱的少子俘获和热发射理论进行合理地解释。鉴于用ＤＬＴＳ技术测量这种陷阱的困难，我们用恒温电容瞬态技术测定它们的空穴表观激活能分别为０．５４和０．５７ｅＶ。它们是新观测到的和Ｂｅ－Ｓｉ共注ＳＩＧａＡｓ有关缺陷。 关键词：     

Influence of surface states on deep level transient spectroscopy in AlGaN/GaN heterostructure

Deep level transient spectroscopy(DLTS) as a method to investigate deep traps in AlGaN/GaN heterostructure or high electron mobility transistors(HEMTs) has been widely utilized.The DLTS measurements under different bias conditions are carried out in this paper.Two hole-like traps with active energies of E_v + 0.47 eV,and E_v + 0.10 eV are observed,which are related to surface states.The electron traps with active energies of E_c-0.56 eV are located in the channel,those with E_c-0.33 eV and E_c-0.88 eV are located in the AlGaN layer.The presence of surface states has a strong influence on the detection of electron traps,especially when the electron traps are low in density.The DLTS signal peak height of the electron trap is reduced and even disappears due to the presence of plentiful surface state.     

分子束外延生长的赝配高电子迁移率晶体管结构中深能级的研究

应用深能级瞬态谱(DLTS)技术详细研究分子束外延生长的Pseudomorphic—high electron mobility transistor(P-HEMT)结构中深能级行为。样品的DLTS表明,在P-HEMT结构的n-AlGaAs层里存在着较大浓度(10¹⁵-10¹⁷cm^-3和俘获截面(10^-16cm²)的高温电子陷阱。它们直接影响着器件性能。高温电子陷阱的产生可能与AlGaAs层里的氧     

Acceptor levels in indium selenide. An investigation by means of the Hall effect,deep-level-transient spectroscopy and photoluminescence

Acceptor levels related to I, II, IV, and V group impurities in indium selenide are studied by means of the Hall effect, deep-level-transient spectroscopy (DLTS) and photoluminescence. Activation energies for hole concentrations in the range from 200 to 300 meV have been measured. A reversible change of sign of the Hall voltage has been observed below 215 K. This behaviour can be explained through a model in which acceptor levels are assumed to be shallow and interlayer planar precipitates of ionized shallow donors create potential wells that behave as deep donors and in which a low concentration of bidimensional free electrons can exist. This model also explains the capacitance-voltage characteristics of both ITO/p-InSe and Au/p-InSe barriers. DLTS results are coherent with this model: hole traps in high concentration located about 570 meV above the valence band are detected. Photoluminescence also confirms the shallow character of acceptor levels. A broad band whose intensity is related to p conductivity appears in the PL spectra of low resistivity p-InSe. The shape and temperature dependence of this band can be explained through self-activated photoluminescence in a complex center in which the ground acceptor level must be at about 50 meV above the valence band.     

Direct-current and radio-frequency characteristics of passivated AlGaN/GaN/Si high electron mobility transistors

AlGaN/GaN/Si HEMTs grown by molecular beam epitaxy have been investigated using spectroscopy capacitance, direct and pulse current–voltage and small-signal microwave measurements. Passivation of the HEMT devices by SiO₂/SiN with NH₃ and N₂O pretreatments is made in order to reduce the trapping effects. As has been found from DLTS data, some of electron traps are eliminated after passivation. This has led to an improvement in the drain current. To describe the electron transport, we have developed a charge-control model by including the deep traps observed from DLTS experiments. The thermal and trapping effects have been, on the other hand, studied from a comparison between direct-current and pulsed conditions. As a result, a gate-lag and a drain-lag were revealed indicating the presence of deep lying centers in the gate-drain spacing. Finally, small-signal microwave results have shown that the radio-frequency parameters of the AlGaN/GaN/Si transistors are improved by SiO₂/SiN passivation and more increasingly with N₂O pretreatment.     

Deep Level Transient Spectroscopy of Defects in High-Energy Light-Particle Irradiated Si

The authors review what has been learned concerning the electrical and annealing properties of point defects in high-energy electron or proton irradiated Si from deep level transient spectroscopy (DLTS). The authors have focused mainly on the properties of electron traps, and to a lesser extent on the properties of hole traps. In addition to an in-depth discussion of hydrogen-related defects in Si, this review article provides a brief tutorial on ion-solid interactions and the theory underlying DLTS. The authors also provide a few examples of the power of high resolution Laplace DLTS in analyzing radiation induced defects. The collection of results gathered in this article may provide the fundamental information for successful defect engineering in light-particle irradiated Si.     

Study of metal-semiconductor interface states using deep level transient spectroscopy

This paper describes the principle of the determination of interface-state parameters by deep level transient spectroscopy (DLTS) and presents a new, simple and exact method to discriminate the DLTS signal due to the emission from interface states from that from bulk traps. The n-type Au-GaAs and Cr-GaAs interfaces have been investigated by the technique. The results obtained in the investigation have revealed the dependences of the energy position, density and capture cross section for the interface states on the metal deposited onto the semiconductor surface, which is consistent with the theoretical prediction by Yndurain and the experimental results obtained by other authors.     

Electric field effects on radiation defects annealing in p-InP

We have performed annealing experiments on electron irradiated Schottky diodes on p-InP. They show a strong influence of the applied reverse bias during annealing on the recovery of the free holes concentration, as well as on the disappearance of the dominant radiation induced hole traps detected by deep level transient spectroscopy (DLTS). Compensating defects are observed to drift under the action of the electric field and accumulate at the edge of the depleted zone, while the main hole traps created by the irradiation anneal faster when empty of holes or subjected to an electric field.     

高温氧化多孔硅的电子束辐照效应

通过高温氧化处理得到的多孔硅,其阴极射线发光谱呈现明显的三峰结构。峰强随电子束辐照时间而下降。对光致发光很弱的样品,电子束辐照后光致发光明显地增强。红外透射谱及Raman谱分析表明样品基本上成为SiO_x.进一步分析指出三峰可能来源于SiO_x中的缺陷中心发光。电子束辐照在SiO_x禁带中引进了一些缺陷能级,通过这些能级使得紫外线可激发样品发光,出现光致发光增强的现象。     

分子束外延生长的n型Al掺杂ZnS1-xTex深中心研究

应用电容-电压、光致荧光和深能级瞬态谱技术研究了分子束外延生长的n型Al掺杂ZnS_1-xTe_x外延层深中心.Al掺杂ZnS_0.977Te_0.023的光致荧光强度明显低于不掺杂的ZnS_0.977Te_0.023，这表明一部分Al原子形成非辐射深中心.Al掺杂ZnS_1-xTe_x(x=0，0.017，0.04和0.046)的深能级瞬态傅里叶 关键词：     

Studies of deep levels in He+-irradiated silicon

9 to 10¹³ particles/cm² have been investigated by the deep level transient spectroscopy technique and capacitance-voltage profiling. Under low fluence irradiation at least four main electron traps have been observed. With further increase in irradiation fluence, two new levels located at E_c-0.56 eV and E_c-0.64 eV appear on the high-temperature side of the DLTS signal. The slope change observed in the amplitude variations of the singly negative charge state of the divacancy versus the dose takes place when these two new levels appear. This suggests that both are multivacancy-related defects. After annealing at 350 °C for 15 min, all electron traps have disappeared. Moreover, no shallow levels are created during the annealing. Received: 12 December 1996/Accepted: 6 May 1997     

Restructuring of defects in silicon by action of subthreshold-energy electrons

The influence of irradiation of silicon p⁺-n diodes by 15 to 30 keV electrons on the deep level transient spectroscopy (DLTS) spectra of the diodes was studied. It was discovered that irradiation leads to the transformation of the DLTS spectra in crystals containing defect clusters. A comparison of the depth of the p-n junction in the crystal with the penetration depth of the electrons indicates that the detected rearrangement of defects is due to secondary electrons diffusing into the p-n junction. A recombination-stimulated mechanism of defect rearrangement is proposed. In crystals containing only point defects, transformation of the DLTS spectra is not observed.Deceased.Translated from Izvestia Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 32–37, June, 1990.     

An investigation of metal/GaAs(100) interfaces by deep level transient spectroscopy

In this work we investigate the ability of DLTS to detect the presence of interface states at metal/GaAs(100) (n-type) interfaces where the semiconductor surface has been prepared by two different procedures. A correlation is observed between the magnitude of the ideality parameter determined from the current-voltage (I-V) characteristic of the diode and presence in the DLTS spectrum of a feature attributable to interface states. Schottky diodes have been fabricated with both gold and iron contacts which exhibit near ideal behaviour (n<1.1). No interface states were detected by DLTS on either of these diodes. However, diodes fabricated on oxidised GaAs surfaces, with higher idealities (1.5 <n < 2), exhibit additional electron trap levels in the DLTS spectrum. For the case of iron, a deep level of activation energy 0.55 eV is observed in the conventional reverse bias pulse sequence mode of DLTS operation. In addition, for both gold and iron diodes, a spectral feature which can be attributed to a broad distribution of interface states within the deplation region is observed during a forward bias pulse sequence.     

注硅半绝缘GaAs的深能级

用深能级瞬态谱(DLTS)详细研究了硅离子注入Liquid-encapsulated Czochralski(缩写为LEC)半绝缘GaAs的深中心。结果表明,在注硅并经高温退火的有源区中观测到4个多子(电子)陷阱,E₀₁,E₀₂,E₀₃和E₀₄。它们的电子表观激活能分别为0.298,0.341,0.555和0.821eV。其中E₀₄与EL2有关,但不是EL2缺陷。E₀₄的电子 关键词：     

A study of electron traps in vapour-phase epitaxial GaAs

The occurence and physical properties of electron traps in device-quality VPEn-GaAs are studied using transient capacitance and DLTS (deep level transient spectroscopy). Four traps labeled A, B, C, and F are seen. Trap A is identified to be the same as the often reported one, commonly attributed to oxygen in substrate material; this trap is also dominant in the VPE layers. The other traps are (to our knowledge) reported here for the first time. No correlation appears to exist between the concentrations of the various traps. The emission rate vs. temperature dependence, a characteristic physical property, is obtained for each of these traps.     

分子束外延生长GaAs/Si异质结电学特性的研究

利用样品Au-GaAs/p-Si的肖特基势垒二极管特性和深能级瞬态谱(DCTS),研究Si衬底上分子束外延生长的GaAs异质结的电学特性。I-V特性表明样品有大的漏电流存在,而快速热退火处理则能使样品I-V特性得以改善,并接近半绝缘GaAs(S.I.GaAs)上生长的Au-GaAs/S.I.GaAs样品的特性,它的来源不是热电子发射或产生-复合电流所引起,而可归结于缺陷参与的隧穿机制,它可通过快速热退火处理得以减小。DCTS谱表明在样品中可观察到Ec-0.41eV和Ec-0.57eV两个电子陷阱,前者可能 关键词：     

Do triboluminescence spectra really show a spectral shift relative to photoluminescence spectra?

There are many reports in the literature of a spectral difference between the triboluminescence (TL) spectrum and the solid-state photoluminescence (PL) spectrum of the same compound. Numerous reasons have been suggested for this difference including pressure-induced changes to Franck-Condon factors during the lifetime of the TL light emission; self-absorption of the TL emission and fracture-induced symmetry changes perturbing the local field of the TL emitting species. However, in a number of cases, the luminescent spectra were recorded on different equipment with different spectral responses, with the resolution of either luminescent spectrum rarely quoted. To avoid artificial spectral differences, care must be taken to account for the response of each equipment over the wavelength range studied, as well as any resolution difference. We have therefore measured the TL and solid-state PL spectra of sixteen TL compounds on the same spectrometer at an identical resolution. Furthermore, the solid-state photoluminescent lifetime has been determined for all samples and the implication that these values have for observing pressure-induced (Franck-Condon) luminescent spectral changes discussed. Finally, in all cases where a significant difference was observed between TL and PL spectra, either self-absorption of the TL emission or fracture-induced perturbations of the local field have been evoked to explain the difference.     

Electrical characterization of impurity-free disordering-induced defects in n-GaAs using native oxide layers

Defects created in rapid thermally annealed n-GaAs epilayers capped with native oxide layers have been investigated using deep-level transient spectroscopy (DLTS). The native oxide layers were formed at room temperature using pulsed anodic oxidation. A hole trap H0, due to either interface states or injection of interstitials, is observed around the detection limit of DLTS in oxidized samples. Rapid thermal annealing introduces three additional minority-carrier traps H1 (E_V+0.44 eV), H2 (E_V+0.73 eV), and H3 (E_V+0.76 eV). These hole traps are introduced in conjunction with electron traps S1 (E_C-0.23 eV) and S2 (E_C-0.45 eV), which are observed in the same epilayers following disordering using SiO₂ capping layers. We also provide evidence that a hole trap whose DLTS peak overlaps with that of EL2 is present in the disordered n-GaAs layers. The mechanisms through which these hole traps are created are discussed. Capacitance–voltage measurements reveal that impurity-free disordering using native oxides of GaAs produced higher free-carrier compensation compared to SiO₂ capping layers. Received: 12 March 2002 / Accepted: 15 July 2002 / Published online: 22 November 2002 RID="*" ID="*"Corresponding author. Fax: +61-2/6125-0381, E-mail: pnk109@rsphysse.anu.edu.au