Characteristics of Germanium n+/p junctions formed by phosphorus diffusion from on indium-gallium-phosphide layer

Although numerous studies have been previously reported for the formation of Ge p–n junctions, there is still a lack of research on Ge junctions formed by solid-phase diffusion doping, which typically uses the diffusion phenomenon of phosphorus (P) atoms from InGaP for the fabrication of a Ge n⁺/p subcell in a III–V multi-junction cell. Here, we investigate the characteristics of Ge n⁺/p junctions achieved by the InGaP-based diffusion technique at 450–650 °C with SIMS, ECV, and J–V analyses. In addition, through a multiple error function fitting method, diffusivity, peak position, and activation energy values are accurately estimated from raw In/Ga/P/Ge SIMS profiles. The extracted activation energy values for In/Ga/P atoms are much lower than previously reported, indicating that a faster diffusion phenomenon occurs during the simultaneous diffusion of In/Ga/P into Ge. A non-annealed InGaP-deposited junction shows Ohmic behavior with a high current density because of leakage currents by many interfacial point defects. After a 550 °C anneal, the current density is reduced by 3–4 orders of magnitude and a small on/off-current ratio is obtained. Compared to this 550 °C annealed junction, a current density increases ∼10 times in the 650 °C sample due to an increased n-type carrier concentration.     

中子嬗变掺杂前后Ge纳米晶的结构和性质

采用第一性原理计算模拟Ge纳米晶在中子嬗变掺杂(NTD)后受空位、O和As杂质的影响.结果表明,退火方法引入的O并不能消除纳米晶中的辐照致空位缺陷的影响,而NTD 产生的As掺杂能补偿这些空位缺陷并消除禁带中产生的杂质能级,从而改善半导体掺杂性能.计算还发现,由于较高的电负性,纳米晶中O对Ge原子较强的吸附作用阻止了空位的形成,导致与缺陷相关的非辐射发光中心的浓度减小,发光效率提高,因此中子辐照掺杂前的高温退火处理是非常有必要的.计算较好地解释了已报道的实验结果. 关键词： Ge纳米晶 中子嬗变掺杂 第一性原理 空位缺陷     

Characteristics of laser-produced Ge ion fluxes used for modification of semiconductor materials

This paper describes the laser generation of Ge ion fluxes and their application to the modification of semiconductor materials by ion implantation. The Ge ions were produced by ablating solid targets using the PALS high-power iodine laser system at the PALS Research Centre in Prague, operating at its third harmonic frequency (438 nm wavelength) and producing 0.4 ns pulses with energy up to 0.25 kJ (intensity≤10¹⁵ W/cm²). The goal of these investigations was optimisation of the implantation of low and medium energy laser-generated Ge ion fluxes and they were carried out as part of the project PALS000929. Recently, a new repetitive pulse laser system at IPPLM in Warsaw, with a wavelength of 1.06 μm, energy of ～0.8 J in a 3.5 ns-pulse, repetition rate of up to 10 Hz, and intensity on target of up to 10¹¹ W/cm², has also been employed to produce Ge ions by irradiating solid targets. The laser-generated ions were investigated with diagnostics based on the time-of-flight method: various ion collectors and an electrostatic ion-energy analyzer. The Ge ion fluxes were implanted into Si and SiO₂ substrates located at distances of 10–30 cm from the target. The SiO₂ films were prepared on single crystal Si substrates and were implanted with Ge ions with different properties. The properties of the Ge-implanted layers, in particular, the depth distributions of implanted Ge ions, were characterised using Rutherford backscattering and other material surface diagnostic methods.     

Ge纳米结构的形貌与铁磁性研究

利用等离子体增强化学气相沉积技术制备了厚度不同的Ge薄膜, 随着样品厚度的减小, 样品表现出了室温铁磁性. 厚度为12 nm样品经过300 ℃退火后, 由于颗粒细化, 颗粒之间的界面增加, 界面缺陷增加, 样品表现出最大的铁磁性 (50 emu/cm³). 场冷却和零场冷却曲线测试表明居里温度约为350 K. 进行600 ℃退火后, 颗粒团聚, 样品的铁磁性最小. 当样品厚度进一步减小为6 nm时, 沉积态样品表现出铁磁性和顺磁性共存. 对6 nm厚的样品进行300 ℃退火后, 样品只具有铁磁性. 进行600 ℃退火后, 样品却只具有顺磁性. 12 nm 和6 nm 厚的Ge纳米结构薄膜随退火温度变化表现出不同的磁性规律, 我们认为是由于样品的颗粒大小和颗粒分布不同造成的. 样品越薄, Si基底与Ge薄膜之间的界面缺陷越明显, 界面缺陷以及Ge颗粒之间的界面缺陷为样品提供了未配对电子, 未配对电子的铁磁性耦合强度与样品颗粒的分布以及颗粒之间的结合有一定的关系. 颗粒之间分散或颗粒之间的融合程度大都将会降低样品的铁磁性.     

能带工程对射频功率SiGe异质结双极晶体管热性能的改善

众所周知,基区"能带工程"可以改善Si_1-xGe _{x 基区异质结双极晶体管(HBT)的直流、频率和噪声等特性,但"能带工程"对HBT热学特性的影响的研究还很少。本文基于三维热电反馈模型,分析了"能带工程"对射频功率SiGe HBT热性能的影响。考虑到电流增益随温度的变化以及发射结电压负温度系数,给出了器件热稳定所需最小镇流电阻(REmin)的表达式,在此基础上给出了非均匀镇流电阻的设计,进一步提高了SiGe HBT的热稳定性 关键词： SiGe HBT Ge组分 热电反馈 镇流电阻}     

A study on the performance of metal-oxide-semiconductor-field-effect-transistors with asymmetric junction doping structure

Diode currents of MOSFET were studied and characterized in detail for the ion implanted pn junction of short channel MOSFETs with shallow drain junction doping structure. The diode current in MOSFET junctions was analyzed on the point of view of the gate-induced-drain leakage (GIDL) current. We could found the GIDL current is generated by the band-to-band tunneling (BTBT) of electrons through the reverse biased channel-to-drain junction and had good agreement with BTBT equation. The effect of the lateral electric field on the GIDL current according to the body bias voltage is characterized and discussed. We measured the electrical doping profiling of MOSFETs with a short gate length, ultra thin oxide thickness and asymmetric doped drain structure and checked the profile had good agreement with simulation result. An accurate effective mobility of an asymmetric source–drain junction transistor was successfully extracted by using the split C–V technique.     

100 keV质子辐照对空间GaAs/Ge太阳电池光电效应的影响

利用空间环境模拟设备,用固定能量为100keV、注量为1×10⁹—3×10¹²cm^-2的质子,对空间实用GaAs/Ge太阳电池进行了辐照试验.利用伏安(I-V)特性、光谱响应和光致发光(PL)光谱测试,研究分析了电池的光电效应.试验表明,电池的各种电性能参数如短路电流(I_sc)、开路电压(V_oc)、最大输出功率(P_{m< 关键词： GaAs/Ge太阳电池 质子辐照 光电效应}     

Investigation of stress and structural damage in H and He implanted Ge using micro‐Raman mapping technique on bevelled samples

The results on structural damage in germanium wafers caused by hydrogen and helium implants of typical doses used in Smart Cut™ Technology (1–6 × 10¹⁶ atoms/cm²) are investigated using Raman mapping and spreading resistance profiling techniques. Raman line‐mapping measurements were performed up to the depth of ~400 nm into a Ge substrate (well beyond the limit of visible light penetration depth) using a bevelling technique. From analysis of the Ge–Ge Raman peak it was found that implantation of H and He introduced a different type of stress, tensile and compressive, respectively and significant structural damage with maximum at the projected range. The obtained data shows that hydrogen incorporation in Ge can act as an acceptor. This is undesirable when the hydrogen ion‐cut technology is applied to high resistivity Ge. The crystalline structure after implantation is completely recovered when annealed at 600 °C for both types of implants. Spreading resistance profiling results reveal that 4−8x10¹⁵ acceptors/cm³ remain after 600 °C, and these are thought to be because of vacancy related defect clusters. Copyright © 2011 John Wiley & Sons, Ltd.     

Electronic and annealing properties of the E0.31 defect introduced during Ar plasma etching of germanium

Low energy (±80 eV) Ar plasma etching has been successfully used to etch several semiconductors, including GaAs, GaP, and InP. We have studied the only prominent defect, E_0.31, introduced in n-type Sb-doped Ge during this process by deep level transient spectroscopy (DLTS). The E_0.31 defect has an energy level at 0.31 eV below the conduction band and an apparent capture cross-section of 1.4×10⁻¹⁴ cm². The fact that no V-Sb defects and no interstitial-related defects were observed implies that the etch process did not introduce single vacancies or single interstitials. Instead it appears that higher order vacancy or interstitial clusters are introduced due to the large amount of energy deposited per unit length along the path of the Ar ions in the Ge. The E_0.31 defect may therefore be related to one of these defects. DLTS depth profiling revealed the E_0.31 concentration had a maximum (6×10¹³ cm⁻³) close to the Ge surface and then it decreased more or less exponentially into the Ge. Finally, annealing at 250 °C reduced the E_0.31 concentration to below the DLTS detection limit.     

Evidence for fast decay dynamics of the photoluminescence from Ge nanocrystals embedded in SiO2

We have investigated the origin of room temperature photoluminescence from ion-beam synthesized Ge nanocrystals (NCs) embedded in SiO₂ using steady state and time-resolved photoluminescence (PL) measurements. Ge NCs of diameter 4-13 nm were grown embedded in a thermally grown SiO₂ layer by Ge⁺ ion implantation and subsequent annealing. Steady state PL spectra show a peak at ∼2.1 eV originating from Ge NCs and another peak at ∼2.3 eV arising from ion-beam induced defects in the SiO₂ matrix. Time-resolved PL studies reveal double exponential decay dynamics on the nanoseconds time scale. The faster component of the decay with a time constant τ₁∼3.1 ns is attributed to the nonradiative lifetime, since the time constant reduces with increasing defect density. The slower component with time constant τ₂∼10 ns is attributed to radiative recombination at the Ge NCs. Our results are in close agreement with the theoretically predicted radiative lifetime for small Ge NCs.     

Infrared electroluminescence from a Si MOS structure with Ge in the oxide

We report on room-temperature infrared electroluminescence (EL) from metal-oxide-semiconductor devices made from Si. We compare the luminescence from RF sputtered oxide films containing SiO₂ with and without Ge by using a composite target and luminescence from a SiO₂ layer made by rapid thermal oxidation. The sputtered films were annealed in the temperature range 600-900 °C. This densifies the films and is likely to reduce the concentration of defects. A luminescence peak located around 1150-1170 nm is observed at current densities as low as 0.1 A/cm². The corresponding photon energy is close to that of the Si band gap. In addition, we observe several broad luminescence bands in the range 1000-1750 nm. These bands get stronger with Ge in the SiO₂ film. Some of these bands have previously been suggested and are directly associated with Ge. Since we observe that the intensity is correlated with the presence of Ge while the mere presence of the bands is not, we discuss the EL bands being due to defects which concentration is influenced by Ge in the oxide.     

Reduction of the annealing temperature of radiation-induced defects in ion-implanted MOS structures

Si-SiO₂ structures irradiated with 11-MeV electrons for 10 s and then implanted with B⁺ ions with an energy of 10 keV at a dose of 1.0×10¹² cm^-2 through the oxide were annealed at different temperatures. MOS capacitors including such oxide layers were studied by quasi-static C/V and thermally stimulated current (TSC) methods. A comparison of the radiation defect annealing of double-treated (electron-irradiated and ion-implanted) samples and of implanted-only samples was carried out. It is shown that a preceding low-dose high-energy electron irradiation of the samples leads to a lowering of the annealing temperature of radiation defects introduced by ion implantation. After annealing at 500 °C for 15 min, no TSC spectra for the double-treated samples were observed. The spectra of the other samples (which were not previously irradiated) showed that after the same thermal treatment only some of the radiation defects introduced by ion implantation are annealed. The difference between the annealed interface state density of previously electron-irradiated and current MOS structures is also demonstrated. A possible explanation of the results is proposed . PACS 61.82.Fk; 85.40.Ry; 61.80.Fe     

Raman spectroscopy of CaM2+Ge2O6 (M2+ = Mg,Mn, Fe,Co, Ni,Zn) clinopyroxenes

The Raman spectra of Ge‐clinopyroxenes CaM²⁺Ge₂O₆ (M²⁺ = Mg, Mn, Fe, Co, Ni, Zn), general formula M2M1T₂O₆, are reported for the first time. Their spectral features are discussed in comparison with corresponding Si‐pyroxenes. The vibrational wavenumbers of germanates may be roughly obtained by a scale factor of about ~0.8 by those of the corresponding silicates, due to the Ge‐Si mass difference. The main peaks in the germanate Raman spectra at ~850 and ~540 cm⁻¹ may be related to Ge‐O tetrahedral stretching and chain bending, respectively; minor peaks between 200 and 400 cm⁻¹ are ascribed to bending and stretching of the non‐tetrahedral cations. Within Ge‐pyroxenes, possible correlations between crystallographic parameters and the vibrational wavenumbers are investigated. The main stretching mode at ~850 cm⁻¹ shows wavenumber changes with M²⁺ substitutions, but no simple correlation can be found with M²⁺ cation mass or size. On the other hand, the chain bending wavenumber linearly decreases with increasing ionic radius of the M²⁺ cation: the expansion of the M1 polyhedron reduces the chain kinking angle and the Ge‐Ge distances correspondingly increase. Copyright © 2015 John Wiley & Sons, Ltd.     

Room-temperature observation of current bistability and fine structures in germanium quantum dots/SiO2 resonant tunneling diodes

The steady-state and time-dependent current–voltage (I–V) characteristics are experimentally investigated in Ge quantum dot (QD)/SiO₂ resonant tunneling diodes (RTDs). Ge QDs embedded in a SiO₂ matrix are naturally formed by thermal oxidation of Si_0.9Ge_0.1 nanowires (30 nm×50 nm) on silicon-on-insulator substrates. The average dot size and spacing between dots are 9±1 and 25 nm, respectively, from TEM observations, which indicate that one or two QDs are embedded between SiO₂ tunneling barriers within the nanowires. Room-temperature resonant oscillation, negative differential conductance, bistability, and fine structures are observed in the steady-state tunneling current of Ge-QD/SiO₂ RTDs under light illumination. Time-dependent tunneling current characteristics display periodic seesaw features as the Ge-QDs RTD is biased within the voltage regime of the first resonance peak while they exhibit harmonic swing behaviors as the RTD is biased at the current valleys or higher-order current peaks. This possibly originates from the interplay of the random telegraph signals from traps at the QD/SiO₂ interface as well as the electron wave interference within a small QD due to substantial quantum mechanics effects.     

Study of the surface cleaning of GOI and SGOI substrates for Ge epitaxial growth

An effective wet cleaning process, optimized for low temperature Ge epitaxial growth on thin Ge or SiGe structures with reduced surface roughening, is proposed. It is found that HF + HCl cleaning is the most effective wet cleaning method that is applicable to the low temperature thermal cleaning. It is also found that temperature of the thermal cleaning appropriate to 25-30 nm thick germanium on insulator (GOI) or silicon-germanium on insulator (SGOI) substrates is approximately 450 °C. Moreover, it is also found that the temperatures of Ge epitaxial growth even in lattice-matched systems must be reduced to around 400 °C to prevent surface roughening and those in lattice-mismatched systems also must be reduced sufficiently (300 °C for strained Ge growth on SGOI (X_eff = 0.6)) to prevent lattice relaxation as well as surface roughening. Finally, the successful formation of the compressively strained GOI structures is demonstrated by applying these wet cleaning and low temperature thermal cleaning processes and low temperature Ge epitaxy to thin SGOI substrates.     

Structural and optical properties of Ge nanocrystals obtained by hot ion implantation into SiO2 and further ion irradiation

In this work, SiO₂ layers containing Ge nanocrystals (NCs) obtained by the hot implantation approach were submitted to an ion irradiation process with different 2 MeV Si⁺ ion fluences. We have investigated the photoluminescence (PL) behavior and structural properties of the irradiated samples as well as the features of the PL and structural recovery after an additional thermal treatment. We have shown that even with the highest ion bombardment fluence employed (2×10¹⁵ Si/cm²) there is a residual PL emission (12% from the original) and survival of some Ge NCs is still observed by transmission electron microscopy analysis. Even though the final PL and mean diameter of the nanoparticles under ion irradiation are independent of the implantation temperature or annealing time, the PL and structural recovery of the ion-bombarded samples have a memory effect. We have also observed that the lower the ion bombardment fluence, the less efficient is the PL recovery. We have explained such behavior based on current literature data.     

离子源辅助电子枪蒸发制备Ge1－xCx薄膜

应用电子枪蒸发纯Ge,考夫曼离子源辅助的方法在Ge基底上沉积了Ge1－xCx薄膜.制备过程中,Ge作为蒸发材料,CH4作为反应气体.通过改变CH4/(CH4+Ar)的气体流量比（G）,制备了G从40％到85％的Ge1－xCx薄膜.应用X射线衍射仪（XRD）测量了Ge1－xCx薄膜的晶体结构,使用傅里叶红外光谱仪（FTIR）测量了2～22 μm的光学透过率,X射线光电子能谱测试（XPS）计算得到C的含量随G的变化关系,用纳米压痕硬度测试计测量了Ge1－xCx薄膜的硬度,原子力显微镜（AFM）测量了G为60％,85％时Ge1－xCx薄膜的表面粗糙度.测试结果表明：制备的Ge1－xCx薄膜在不同的G值下均为无定形结构.折射率随着G值的增加而减小,在3.14～3.89之间可变,并具有良好的均匀性以及极高的硬度.     

A non‐destructive approach for doping profiles characterization by micro‐Raman spectroscopy: the case of B‐implanted Ge

B‐implanted Ge samples have been investigated by micro‐Raman spectroscopy under different excitation wavelengths, with the aim of gaining insights about the B distribution at different depths beneath the sample surface. The intensities, observed under the different excitation wavelengths, of the B–Ge Raman peak at about 545 cm⁻¹, which is due to the local vibrational mode of the substitutional B atoms in the Ge matrix, have been used to calibrate the optical absorption lengths in B‐implanted Ge. Then, by using these calibrated values, a very sharp correlation between the spectral features of the Ge–Ge Raman peak at ~300 cm⁻¹ and the content of substitutional B atoms has been derived. Accordingly, a non‐destructive approach, based on micro‐Raman spectroscopy under different excitation wavelengths, is presented to estimate, at least at the lowest depths, the carrier concentration profiles from the spectral features of the Ge–Ge Raman peak. Copyright © 2014 John Wiley & Sons, Ltd.     

Effect of oxygen deficiency on the radiation sensitivity of sol-gel Ge-doped amorphous SiO2

We report experimental investigation by electron paramagnetic resonance (EPR) measurements of room temperature γ-ray irradiation effects in sol-gel Ge doped amorphous SiO₂. We used materials with Ge content from 10 up to 10⁴ part per million (ppm) mol obtained with different preparations. These latter gave rise to samples characterized by different extents of oxygen deficiency, estimated from the absorption band at ~5.15 eV of the Ge oxygen deficient centers (GeODC(II)). The irradiation at doses up to ~400 kGy induces the E'-Ge, Ge(1) and Ge(2) paramagnetic centers around g ~ 2 with concentrations depending on Ge and on GeODC(II) content. We found correlation between Ge(2) and GeODC(II) contents, supporting the suggestion that the latter defect is the precursor of Ge(2). Even if the concentration of E'-Ge and Ge(1) defects cannot be strictly related to GeODC(II) one, the concentration growth of these paramagnetic defects with irradiation evidences that the radiation sensitivity is enhanced by the oxygen deficiency for Ge doping above 1000 ppm mol and it is reduced below 100 ppm mol. Moreover, the investigation of samples with different GeODC(II) concentration but fixed Ge content has shown that the oxygen deficiency enhances the overall radiation sensitivity for [GeODC(II)]/[Ge] in the range 10^-3 10^-2.     

Deep level defects in gamma-ray irradiated ge doped with pb or sn

Abstract

Deep level transient spectroscopy has been used to investigate the electrical properties of deep defect states in γ-ray irradiated Ge doped with the isoelectronic elements Pb or Sn. Three deep levels are observed in the irradiated Pb-doped Ge (E_v +0.28 eV, E_c ?0.33 eV, E_c ?0.39 eV) and two deep levels observed in the Sn-doped Ge (E_v + 0.19 eV, E_c ?0.15 eV). For the same γ-ray irradiation doses, Ge crystals grown from graphite crucibles and doped with Pb or Sn shows about two-thirds the total density of deep level defects observed in undoped Ge grown from synthetic quartz crucibles. All of the defect states observed were removed by a 1 hour, 250°C thermal anneal, and all but the E_c ?0.39 eV state in the Pb-doped material were neutralized by exposure to a low pressure atomic hydrogen plasma.