Shallow junction formation on p-like CdTe crystals by indium diffusion using excimer laser annealing

Excimer laser annealing has been investigated to form a shallow junction on p-like CdTe crystals by indium diffusion. By evaporating a thin layer of indium on the CdTe crystals in a physical vapor deposition system without heating the crystals, and then irradiating them with an excimer laser, we could produce a highly conductive thin surface layer on the crystal. These layers showed n-type conductivity in Hall measurements, and an increase on the donor-acceptor pair band, possibly due to indium incorporation, was also observed in the photoluminescent spectrum. The best value of resistivity, carrier concentration and electron mobility of the layer thus obtained was 5 10⁻³ cm, 9 10¹⁸ cm⁻³, and 138 cm²/Vs, respectively. The carrier transport properties of the shallow p-n junction formed were then investigated by means of current-voltage measurements at different temperatures. Furthermore, applicability of this junction in a gamma-ray detector was also investigated.     

一种双扩散p阱nMOS器件新结构

本文介绍了一种适用于ＶＤＭＯＳ功率集成电路的双扩散ｐ阱ｎＭＯＳ器件新结构，该结构具有与ＶＤＭＯＳ工艺完全兼容和加工工艺简单的特点。利用这种结构可实现ｎＭＯＳ处理电路与衬底间的ｐｎ结隔离，并且隔离电压接近ＶＤＭＯＳ管的耐压。通过调节源、漏扩散窗口间距，可以在小范围内调整ｎＭＯＳ管的阈值电压。这种双扩散ｎＭＯＳ器件结构，特别适合于制作单驱动器件的ＭＯＳ功率集成电路。     

Two Steps B Ion-Implantation of Diamond Film Grown on an n-Type Si Substrate and Its p-n Junction Effects

Polycrystalline diamond thin films are deposited on an n-type Si substrates by hot filament chemical vapor deposition,and then are implanted with boron ions in a 200keV ion implanter.In order to achieve a better distribution of the implanted element,boron ions are implanted by two steps:implanting boron ions with the energy of 70keV first,and then with the energy of 100keV.The homogeneous distribution of the B ion is gained.The current-voltage characteristics of the samples are studied.It is found that the p-n heterojunction effect is achieved in these samples.     

Photoluminescence and raman studies of high quality CdTe:I Epilayers

Low-temperature photoluminescence (PL) studies of iodine-doped CdTe epilayers have been performed. A compensating acceptor center which gives rise to deep-level PL emission at 1.491 eV is identified. From selective excitation PL studies, we assign this 1.491 eV line to the recombination of an associate donor-acceptor close pair, consisting of nearest neighbor substitutional sodium and iodine atoms (Na_Cd-I_Te). This neutral defect complex has a localized mode of 36.5 meV, which is much larger than the bulk CdTe lattice mode of 21.3 meV. The electronic energy level associated with this defect is 115 meV below the conduction band. Also, we use a combination of selective excitation PL and Raman spectroscopies to determine the ionization energy of the isolated shallow iodine donor (I_Te) in CdTe. We find that the donor binding energy of this anion-site hydrogenic donor is 15.0 (±0.2) meV.     

In situ monitoring of photovoltaic properties in organic solar cells during thermal annealing

This paper reports a simple and useful technique that monitors the changes of poly(3-hexylthiophene) (P3HT):1-(3-methoxycarbonyl)-propyl-1-phenyl-(6,6)C₆₁-based organic solar cells (OSCs) during thermal annealing in situ. Thermal annealing was divided into five stages in which the variations of the cell parameters were obtained in detail. Annealing temperature that was higher than the glass transition temperature of P3HT (127 °C) was found critical to the improvement of open-circuit voltage. The initial rise of the short-circuit current was explained by in situ monitoring of the transport behaviors of electrons and holes. Finally, in situ monitoring was adopted to compare OSCs that were or were not solvent-annealed, indicating the effectiveness in optimizing, modeling and understanding in depth the effects of the thermal annealing of OSC with a blended active layer.     

Rapid thermal annealing of ion implanted cdte

Rapid thermal annealing of ion implantedn-type CdTe has been investigated. Samples were implanted with 60 keV Ar⁺ and As⁺ ions to a dose of 1 × 10¹⁴ cm⁻² and subjected to anneal sequences of 5-100s at temperatures of 350-650° C. Photoluminescence measurements have indicated that the implantation completely quenches the photoluminescence; however, anneals for only 5s at 350° C are sufficient to recover most of the features of the photoluminescence spectrum to that equivalent of unimplanted material. Luminescence spectral features associated with thermal annealing damage and substitutional As in inferred. Type conversion of the As⁺ implanted layer is observed and it has been shown that good diodes can be made, with the best behaviour resulting from a 5s anneal at 450° C. Research supported by the Natural Sciences and Engineering Research Council of Canada     

HgCdTe光伏器件反常I－V特性分析

对ＨｇＣｄＴｅ光伏器件研制中出现的光电二极管伏安特性反常现象提出了寄生ｐ－ｎ结模型，并以此模型为基点，结合工艺实验对此现象进行了解释和分析。     

Characterization of small area laser beam annealing

The structure of small area (∼10 micron diameter) spots produced by Q-switched pulsed laser irradiation of n-type silicon covered by a thin film of sputtered aluminum have been studied. Spatially resolved SIMS analysis has been combined with SEM observations to characterize the resulting microstructure. Careful analysis of the SIMS results indicate the spots display subsurface alloying and deep (∼1 μm) aluminum penetration.     

Diffusion of phosphorus in CdTe

The diffusion of phosphorus in CdTe was measured as a function of anneal time and temperature in the temperature range 600–900°C. The diffusion anneals were carried out in evacuated silica capsules mainly with traces of radioactive phosphorus in the capsule along with sufficient cadmium metal to maintain a saturated vapor pressure over the CdTe slice throughout each anneal. The concentration profiles were measured using a radiotracer sectioning technique. Diffusion anneals were carried out also using other conditions, including some with excess tellurium in the capsule in place of the cadmium. The diffusion profiles were single component. The standard erfc function gave satisfactory fits to the profiles which were Fickian in nature except for short anneal times at intermediate temperatures. When the diffusivity was plotted on an Arrhenius graph, a straight line was obtained giving an activation energy of 2.0 eV. The surface concentration at each temperature was independent of time and varied in value between 1.5×10¹⁶ cm⁻³ at 600°C to 1×10¹⁸ cm⁻³ at 900°C. When the results were plotted on an Arrhenius graph, the results gave a straight line with an activation energy of 1.3 eV.     

从多子角度阐述p-n结理论

传统方法在分析p-n结理论时仅仅关注了过剩少子的扩散电流,但是随着其浓度梯度的降低,扩散电流趋于零,则电流的连续性将难以理解。另外,如果仅仅考虑过剩少子的注入,则无法理解"中性区"的电中性(即电中性条件将被破坏)。针对以上矛盾,以基本的器件物理为基础,分析并得到过剩多子必然存在于中性区,且其分布和数量与过剩少子相同,因而过剩多子的扩散电流也参与p-n结的电流输运。在充分考虑过剩多子的基础上,对p-n结的工作机理可以有更好、更深刻的理解。理想二极管方程在一些假设下仅仅考虑了空间电荷区两边过剩少子的扩散电流,提供了一个很巧妙地计算总电流的方法。     

Rapid capless annealing of28Si,64Zn,and9Be implants in GaAs

We report the use of tungsten-halogen lamps for rapid (−10 s) thermal annealing of ion-implanted (100) GaAs under AsH₃/Ar and N₂ atmospheres. Annealing under flowing AsH₃/Ar was carried out without wafer encapsulation. Rapid capless annealing activated implants in GaAs with good mobility and surface morphology. Typical mobilities were 3700–4500 cm²/V-s for n-layers with about 2×10¹⁷cm⁻³ carrier concentration and 50–150 cm²/v-s for 0.1–5xl0¹⁹ cm⁻³ doped p-layers. Rapid thermal annealing was performed in a vertical quartz tube where different gases (N₂, AsH₃/H₂, AsH₃/Ar) can be introduced. Samples were encapsulated with SiO when N₂ was used. Tungsten-halogen lamps of 600 or 1000 W were utilized for annealing GaAs wafers ranging from 1 to 10 cm² in area and 0.025 to 0.040 cm in thickness. The transient temperature at the wafer position was monitored using a fine thermocouple. We carried out experiments for energies of 30 to 200 keV, doses of 2×10¹² to 1×10¹⁵ cm⁻², and peak temperatures ranging from 600 to 1000‡C. Most results quoted are in the 700 to 870‡C temperature range. Data on implant conditions, optimum anneal conditions, electrical characteristics, carrier concentration profiles, and atomic profiles of the implanted layers are described. Presented at the 25th Electronic Materials Conference, Burlington, VT, June 22, 1983.     

Growth and optical characterization of strained CdZnTe/ CdTe quantum wells

We have grown strained Cd_1-xZn_xTe(x ≈ 0.2)/CdTe single and multiple quantum wells by molecular beam epitaxy. GaAs was used as a substrate. The well widths were systematically increased until the critical thickness was exceeded. Low-temperature (liquid helium) photoluminescence (PL) spectroscopy was used to characterize the films. Two prominent PL peaks were observed: one arising from the quantum well and the other from the barrier material. The energy of the quantum well luminescence is consistent with theory when strain is included. The critical layer thickness for the CdTe quantum wells was found to be between 150 and 175 å, in agreement with the model of Matthews and Blakeslee.     

A study of the ion implantation damage and annealing behavior in GaSb

The effects of damages produced by implantation of Te, Er, Hg, and Pb ions into undoped (100) GaSb single crystals and their recovery by Rutherford backscattering (RBS)/channeling were investigated. The implantations with dosages in the range of 10¹³ to 10¹⁵ ions/cm² were carried out at liquid nitrogen temperature, at energies corresponding to a projected range of 447Å in GaSb. Near surface damage equivalent to that of an amorphous layer was observed even at lower doses. The samples were annealed at 600°C for different durations, with the Te implanted sample of the lowest dosage exhibiting the best recovery (Χ_min = 11%) compared to others. This value of Χ^min nearly corresponds to that of the virgin crystal. Examination of the surface morphology as a function of mass, dosage, and annealing duration revealed that it was strongly influenced by the dosage of the implanted ions.     

Rapid thermal annealing effects on the photoluminescence properties of molecular beam epitaxy-grown GaIn(N)As quantum wells with Ga(N)As spacers and barriers

This article describes the effects of rapid thermal annealing (RTA) on the photoluminescence (PL) emission from a series of GaIn(N)As quantum wells. Indium compositions of both 20% and 32% were examined with nominal N compositions of 1% or 2%. The N location was varied within our quantum structure, which can be divided into three regions: (1) quantum well, (2) Ga(N)As spacer layers at the barrier-to-well interface and well-to-barrier interface, and (3) barriers surrounding each quantum well. Eight combinations of samples were examined with varying In content, Ga(N)As spacer layer thickness, N content, and N location in the structure. In the best cases, the presence of these Ga(N)As spacer layers improves the PL properties, due to annealing, with a reduction in the emission wavelength blueshift by ～400 Å, a reduction of the decrease in the full-width at half-maximum (FWHM) by ～5 meV, and a threefold reduction of the increase in integrated intensity. It was also observed that relocating N from the quantum wells to the barriers produces a comparable emission wavelength both before and after annealing. Our results further show that the composition of incorporated N in the material is most influential during the stages of RTA in which relatively small amounts of thermal energy is present from our lower annealing times and temperatures. Hence, we believe a low thermal-energy anneal is responsible for the recovery of the plasma-related crystal damage that was incurred during its growth. However, the In composition in the quantum well is most influential during the latter stages of thermal annealing, at increased times and temperatures, where the wavelength blueshift was roughly independent of the amount of incorporated N. As a result, our investigations into the effects of RTA on the PL properties support other reports that suggest the wavelength blueshift is not due to N diffusion.     

Experimental investigation of the excess charge

The open-circuit voltage of about 600 mV developed by 0.1 ohm-cm silicon solar cells under air mass zero illumination is about 100 mV less than voltages predicted from simple diffusion theory. The lower measured voltages appear to be controlled by junction current transport processes associated with the thin top diffused layer. Mechanisms such as low n⁺ layer minority carrier lifetime and bandgap narrowing due to heavy doping effects (HDE) have been suggested to explain these results. Experimental determinations of the properties of the diffused layer are required to assess which of these mechanisms predominate. While direct measurement is difficult, an indirect measurement methodology exists by which the lifetime or transit time in the diffused layer can be obtained. Nine p-type, 1×2 cm, 〈111〉 orientation silicon wafers were phosphorus diffused at 880°C for 45 minutes using P0Cl₃. Open-circuit voltages of 595-612 mV, typical of all 0.1 ohm-cm cell voltages, were obtained. From the open-circuit voltage and short-circuit current, the diffusion controlled I₀ was obtained. In addition to illuminated I-V characteristics, the time constants from the Open-Circuit Voltage Decay method, and the minority carrier diffusion lengths in the base region were measured. The base region charge was determined using the base region diffusion length measured by an X-ray method. The data from these experiments combined with simple theory can imply the minority carrier time constant and the excess charge in the diffused layer. From this, certain conclusions are drawn about the relative roles of bandgap shrinkage and recombination rates in the diffused layer.     

Effect of annealing conditions on the uniformity of undoped Semi-Insulating InP

Recently, it was found that undoped semi-insulating InP can be obtained by highpressure annealing of high purity materials. The reproducibility and the uniformity was, however, not satisfactory. In the present work, we found that not only Fe concentrations but also Cr and Ni concentrations in annealed wafers were slightly increased during annealing. Since it seems that the origin of the contamination was due to the vapor source of red phosphorus, conductive InP with a trace amount of Fe was annealed under low phosphorus vapor pressure in order to reduce the contamination. By preventing the contamination of Cr and Ni, preparation of semi-insulating InP became highly reproducible. The minimum Fe concentration for realizing semi-insulating InP was found to be 1 x 10¹⁵cm⁻³. It was also found that the better resistivity uniformity can be obtained at higher annealing temperatures.     

Diffusion of iodine into CdTe at room temperature

Studies on the diffusion of iodine into CdTe at a temperature of 20°C using four widely differing types of diffusion sources are compared and discussed. The concentration profiles were measured using either a radiotracer sectioning (RTS) technique or secondary ion mass spectrometry (SIMS). The profiles were composed of four parts to which a computer package consisting of the sum of four complementary error functions (erfc) gave accurate fits, providing four empirical values of the diffusivity. The diffusivities for the fastest component in all four cases were in agreement (～2 × 10^?14 cm² s^?1) and were consistent with previously published data. These results indicate that when iodine is diffused from the vapour it is not a suitable long-termstable dopant in devices where sharp junctions are required.     

Investigation of HgCdTe p-n device structures grown by liquid-phase epitaxy

The microstructure of p-n device structures grown by liquid-phase epitaxy (LPE) on CdZnTe substrates has been evaluated using transmission electron microscopy (TEM). The devices consisted of thick (∼21-μm) n-type layers and thin (∼1.6-μm) p-type layers, with final CdTe (∼0.5 μm) passivation layers. Initial observations revealed small defects, both within the n-type layer (doped with 8×10¹⁴/cm³ of In) and also within the p-type layer but at a much reduced level. These defects were not visible, however, in cross-sectional samples prepared by ion milling with the sample held at liquid nitrogen temperature. Only isolated growth defects were observed in samples having low indium doping levels (2×10¹⁴/cm³). The CdTe passivation layers were generally columnar and polycrystalline, and interfaces with the p-type HgCdTe layers were uneven. No obvious structural changes were apparent in the region of the CdTe/HgCdTe interfaces as a result of annealing at 250°C.     

Modification of electronic and chemical structure at metal/cdte interfaces by pulsed laser annealing

We have measured the effects of metallization and thermal processing on the chemical interaction, band bending, and deep level formation at Au and In/CdTe interfaces using soft x-ray photoemission, photoluminescence, cathodoluminescence, and surface photovoltage spectroscopies. Metallization and laser processing induce major increases in the intensity of several deep photoluminescence transitions. Core level shifts and cathodoluminescence spectra show Fermi level movements characteristic of both a classical work function model and chemically-induced defect pinning. Both interfaces displayed staged Fermi level movements with the evolving metal-semiconductor interaction. Intermediate and final Fermi energies for both systems correlated with the energies of the processing-enhanced photoluminescence transitions, suggesting that the states associated with these transitions are determining the Fermi level.