Double Crystal X-ray Diffraction Research Articles

Characterization of 4H-SiC Homoepitaxial Films on Porous 4H-SiC from Bis(trimethylsilyl)methane Precursor

4H-SiC homoepitaxial films were grown on 8° off-axis porous 4H-SiC (0001) faces in the temperature range of by chemical vapor deposition from bis(trimethylsilyl)methane (BTMSM) precursor. The activation energy for growth was 5.6 kcal/mol, indicating that the film growth is dominated by the diffusion-limited mechanism. Triangular stacking faults were incorporated in the SiC thin film grown at low temperature of 1280°C due to the formation of 3C-SiC polytype. Moreover, super-screw dislocations appeared seriously in the SiC film grown below 1320°C. Clean and featureless morphology was observed in the SiC film grown below 25 standard cubic centimeters per minute (sccm) carrier gas flow rate of BTMSM at 1380°C while 3C-SiC polytype with double positioning boundaries grew at 30 sccm flow rate of BTMSM. The dislocation density of the epi layer was strongly influenced by the growth temperature and flow rate of BTMSM. Double axis crystal X-ray diffraction and optical microscopy analysis revealed that the dislocation density decreased at the higher growth temperature and lower flow rate of BTMSM. The full width at half maximum of the rocking curve of the film grown at optimized condition was 7.6 arcsec and the sharp free exciton and Al bound exciton lines appear in the epi layer, which indicates that the 4H-SiC film was of very high quality. © 2003 The Electrochemical Society. All rights reserved.

The Effects of Sapphire Surface Treatments and Nitridation on GaN Nucleation Grown using Hydride Vapor Phase Epitaxy

AbstractWe have studied the effects of sapphire surface treatments and nitridation on GaN nucleation grown using the hydride vapor phase epitaxy technique. The surface treatments used were airannealing at 1400°C, etching in pure H2SO4 at 250°C, and etching in a 3:1 mixture of H2SO4:H3PO4 solution at 250°C. A nitridation step was carried out using 20% NH3 in N2 gas mixture at 1100°C. GaN nucleation and the early stage s of growth was investigated by short time growth and quench experiments. Atomic force microscopy and double crystal x-ray diffraction were used to examine the sapphire surface morphology, GaN island density, and GaN island structure. A lower density of GaN islands was grown on the air-annealed sapphire compared to the H2SO4-etched and 3:1 H2SO4:H3PO4-etched sapphire. GaN islands grown on the 3:1 H2SO4:H3PO4-etched sapphire had a broad mosaic spread due to preferential growth on surface pits. Sapphire nitridation resulted in a higher GaN island density with a smaller mosaic spread. A high density and uniform nucleation of GaN islands is critical in producing high quality thick GaN films. The H2SO4-etched sapphire and nitridation resulted in a high density of uniform GaN islands.

XRD Study of Quantum-Well Heterostructures

Heterostructures implementing InAs quantum dots in a GaAs matrix are fabricated and examined by double-crystal XRD. Structural parameters of the layers and interfaces are evaluated. It is shown that the structural quality of the cap layer is affected by its doping level.

In x Ga 1–x As Strained-Layer Quantum Well in a Pseudomorphic Heterostructure: High-Resolution XRD Characterization for Different Quantum-Well Thicknesses

Strained-layer quantum wells of different thicknesses are realized in the form of an n-Al0.25Ga0.75As/InxGa1 – xAs/GaAs pseudomorphic heterostructure. The structural properties of the quantum wells are determined by high-resolution double-crystal XRD and by photoluminescence spectroscopy. The depth profile of In mole fraction is derived from the rocking curves. It indicates that the quantum-well interfaces are strongly smeared and hence their In mole fractions are less than the target value, 0.19. The XRD data are compared with the photoluminescence ones.

Al x Ga 1 – x As/GaAs/Al x Ga 1 – x As Double Quantum Well with a Thin AlAs Interwell Barrier: Structural Characterization by SIMS and XRD

An Al x Ga1 – xAs/GaAs/Al x Ga1 – xAs double quantum well with a thin AlAs interwell barrier is examined by SIMS and double-crystal XRD for an AlAs thickness of about 10 or 18 A. Thickness and other structural parameters are determined for each layer. The rocking curves are found to indicate a fairly abrupt interwell barrier.

Microfocus x-ray study of selective area epitaxy of SiGe on Si

We describe an x-ray microprobe measurement of selectively grown heteroepitaxial Si1−xGex on Si. The experiment was conducted at the European Synchrotron Radiation Facility of Grenoble at the ID13 Microfocus beamline. The Si1−xGex layers were deposited by a standard chemical vapor deposition process on patterned 200 mm wafers of monocrystalline Si substrate. The uniformity of the pseudomorphic layers, in terms of Ge content and thickness, is evaluated by double crystal x-ray diffraction with the use of a novel microgoniometer and with a spatial resolution of ∼5×7.5 μm2. The results show the good uniformity of the SiGe layers and indicate the possibility of evaluating the strain fields near the shallow trench isolation structures.

Heavy carbon doping of GaAs by MOVPE using a new dopant source CBrCl 3 and characterization of the epilayers

A new dopant source of carbon trichloro-bromide (CBrCl 3), an inter-substituted compound of two highly efficient dopants viz. CCl 4 and CBr 4, has been used for the heavy carbon doping of GaAs in metal organic vapor phase epitaxy (MOVPE) growth. High doping level of 1.12×10 20 cm −3 was achieved at growth temperature of 600°C and V/III ratio of 10. Self-compensation in the samples was systematically studied using the double crystal X-ray diffraction, Hall and photoluminescence measurements. Samples with hole concentration up to 7.36×10 19 cm −3 were free of compensation, while those with higher hole concentrations were found to be compensated. Compensations of the layers were calculated quantitatively from conventional lattice mismatch measurements. Anti-site incorporation of carbon was found to be the dominant compensation mechanism for hole concentration above 7.36×10 19 cm −3.

Structural and optical characterization of rapid thermally annealed InAs/In 0.15Ga 0.85As dots-in-well structure

Rapid thermal annealing studies were performed on a 10-stack InAs/In 0.15Ga 0.85As dots-in-well (DWELL) heterostructure at four different temperatures of 700°C, 750°C, 800°C and 850°C. Optical and structural characterization were performed, using photoluminescence (PL) and double crystal X-ray diffraction (DCXRD) techniques. Based on the calculations and analysis of the PL peak positions and linewidths, the changes in the perpendicular and parallel lattice constants and the average indium composition in the DWELL structure were determined. Increased In/Ga interdiffusion along the growth direction and a thermally induced strain relaxation was observed. Good correlation between PL and XRD measurements has also been obtained.

Epitaxial growth and characterization of SiC on C-plane sapphire substrates by ammonia nitridation

The growth of SiC epilayers on C-face (0 0 0 1) sapphire (α-Al 2O 3) has been performed using CVD method. We found that the quality of SiC epilayers has been improved through the nitridation of substrates by exposing them to ammonia ambient, as compared to growth on bare sapphire substrates. The single crystallinity of these layers was verified by XRD and double crystal XRD measurements. Atomic force microscopy was used to evaluate the surface morphology. Infrared reflectivity and Raman scattering measurement were carried out to investigate the phonon modes in the grown SiC. Detailed Raman analysis identified the 6H nature of the as-grown SiC films.

DOPING AND GROWTH OF THIN Si EPILAYER AND SiGe BY UHV/CVD

The real time B-doped thin Si and SiGe epilayers on diameter 3-inch Si substrates were grown by an ultrahigh vacuum chemical vapor deposition (UHV/CVD) system. The substrate temperature during growth was from 550 ~ 780°C. The properties of the epilayers were characterized by secondary ion mass spectrum (SIMS), Fourier transform infrared spectroscopy (FTIR), spreading resistance profile (SRP) and double crystal x-ray diffraction (DCXRD). The carrier concentration in the intrinsic Si epilayer was about 1012 cm -3 and the resistivity was as high as about 10000 Ωcm. In addition, the abrupt transition and B-doped concentration of 1015 ~ 1019 cm -3 were achieved for Si and SiGe epilayers.

In 0.25Ga 0.75As growth on low-temperature thin buffer layers formed on GaAs (0 0 1) substrate

High-quality In 0.25Ga 0.75As films were grown on low-temperature (LT) ultra-thin GaAs buffer layers formed on GaAs (0 0 1) substrate by molecular beam epitaxy. The epilayers were studied by atomic force microscopy (AFM), photoluminescence (PL) and double crystal X-ray diffraction (DCXRD). All the measurements indicated that LT thin buffer layer technique is a simple but powerful growth technique for heteroepitaxy.

Crystallographic tilt in GaN layers grown by epitaxial lateral overgrowth

The crystallographic tilt in GaN layers grown by epitaxial lateral overgrowth (ELO) on sapphire (0001) substrates was investigated by using double crystal X-ray diffraction (DC-XRD). It was found that ELO GaN stripes bent towards the SiNx mask in the direction perpendicular to seeding lines. Each side of GaN (0002) peak in DC-XRD rocking curves was a broad peak related with the crystallographic tilt. This broad peak split into two peaks (denoted as A and B), and peak B disappeared gradually when the mask began to be removed by selective etching. Only narrow peak A remained when the SiNx mask was removed completely. A model based on these results has been developed to show that there are two factors responsible for the crystallographic tilt: One is the non-uniformity elastic deformation caused by the interphase force between the ELO GaN layer and the SiNx mask. The other is the plastic deformation, which is attributed to the change of the threading dislocations (TDs)-from vertical in the window regions to the lateral in the regions over the mask.

Hot Wall Epitaxy(HWE)법에 의한 Cdln2S4단결정 박막 성장과 열처리 효과

A stoichiometric mixture of evaporating materials for CdIn<TEX>$\_$</TEX>2/S<TEX>$\_$</TEX>4/ single crystal thin films was prepared from horizontal furnace. To obtain the single crystal thin films, CdIn<TEX>$\_$</TEX>2/S<TEX>$\_$</TEX>4/ mixed crystal was deposited on thoroughly etched semi-insulating GaAs(100) substrate by hot wall epitaxy(HWE) system. The source and substrate temperatures were 630 <TEX>$\^{C}$</TEX> and 420 <TEX>$\^{C}$</TEX>, respectively. The crystalline structure of single crystal thin films was investigated by the photoluminescence and double crystal X-ray diffraction(DCXD). The carrier density and mobility of CdIn<TEX>$\_$</TEX>2/S<TEX>$\_$</TEX>4/ single crystal thin films measured from Hall effect by van der Pauw method are 9.01<TEX>$\times$</TEX>10<TEX>$\^$</TEX>16/ cm<TEX>$\^$</TEX>-3/ and 219 ㎠/V<TEX>$.$</TEX>s at 293 K, respectively. From the optical absorption measurement, the temperature dependence of energy band gap on CdIn<TEX>$\_$</TEX>2/S<TEX>$\_$</TEX>4/ single crystal thin films was found to be Eg(T) ＝ 2.7116 eV - (7.74 <TEX>$\times$</TEX> 10<TEX>$\^$</TEX>-4/ eV) T<TEX>$\^$</TEX>2//(T＋434). After the as-grown CdIn<TEX>$\_$</TEX>2/S<TEX>$\_$</TEX>4/ single crystal thin films was annealed in Cd-, S-, and In-atmospheres, the origin of point defects of CdIn<TEX>$\_$</TEX>2/S<TEX>$\_$</TEX>4/ single crystal thin films has been investigated by the photoluminescence(PL) at 10 K. The native defects of V<TEX>$\_$</TEX>cd/, V<TEX>$\_$</TEX>s/, Cd<TEX>$\_$</TEX>int/ and S<TEX>$\_$</TEX>int/ obtained by PL measurements were classified as donors or accepters type. And we concluded that the heat-treatment in the S-atmosphere converted CdIn<TEX>$\_$</TEX>2/S<TEX>$\_$</TEX>4/ single crystal thin films to an optical p-type. Also, we confirmed that In in CdIn<TEX>$\_$</TEX>2/S<TEX>$\_$</TEX>4/GaAs did not from the native defects because In in CdIn<TEX>$\_$</TEX>2/S<TEX>$\_$</TEX>4/ single crystal thin films existed in the form of stable bonds.

Characteristics of molecular beam epitaxy-grown GaFeAs

Abstract Diluted magnetic semiconductors GaFeAs were grown by molecular beam epitaxy and characterized. Ga 1− x Fe x As ternary alloys were obtained at the growth temperature T s =200 °C ranging from x =0.005 to 0.03. The effects of thermal treatment on behaviors of defects, affecting to the magnetic properties of GaFeAs layer were particularly elucidated. As-grown samples were annealed at temperatures varying from 400 to 600 °C. From the measurement of double crystal X-ray diffraction, we observed Fe-related peak which shifted to a higher diffraction angle as the Fe content increased, indicating that the lattice constant decreases with increasing Fe content. In contrast, above the annealing temperature 500 °C, the lattice constant becomes smaller than that of GaAs. Using the deep level transient spectroscopy, various defects in GaFeAs layer were observed and identified in conjunction with magnetic properties.

Hot Wall Epitaxy 법에 의한 CdIn2S4단결정 박막의 성장과 광전류 특성

수평 전기로에서 <TEX>$CdIn_2S_4$</TEX> 다결정을 합성하여 HWE(Hot Wall Epitaxy)방법으로 <TEX>$CdIn_2S_4$</TEX> 단결정 박막을 반절연성 GaAs (100)기판에 성장시켰다. <TEX>$CdIn_2S_4$</TEX> 단결정 박막의 성장 조건은 증발원의 온도 <TEX>$630^{\circ}C$</TEX>, 기판의 온도 <TEX>$420^{\circ}C$</TEX>였고 성장 속도는 <TEX>$0.5\;{\mu}m/hr$</TEX>였다. <TEX>$CdIn_2S_4$</TEX> 단결정 박막의 결정성의 조사에서 10 K에서 광발광(photoluminescence) 스펙트럼이 463.9 nm (2.6726 eV)에서 exciton emission 스펙트럼이 가장 강하게 나타났으며, 또한 이중 결정 X-선 요동 곡선(DCRC)의 반폭치(FWHM)도 127 arcsec로 가장 작아 최적 성장 조건임을 알 수 있었다. Hall 효과는 van der Pauw 방법에 의해 측정되었으며, 온도에 의존하는 운반자 농도와 이동도는 293K에서 각각 <TEX>$9.01{\times}10^{16}/cm^3$</TEX>, <TEX>$219\;cm^2/V{\cdot}s$</TEX>였다. <TEX>$CdIn_2S_4$</TEX>/SI(Semi-Insulated) GaAs(100) 단결정 박막의 광흡수와 광전류 spectra를 293K에서 10K까지 측정하였다. 광흡수 스펙트럼으로부터 band gap <TEX>$E_g(T)$</TEX>는 Varshni 공식에 따라 계산한 결과 <TEX>$2.7116eV-(7.74{\times}10^{-4}eV/K)T^2$</TEX>/(T+434K)이었으며 광전류 스펙트럼으로부터 Hamilton matrix(Hopfield quasicubic mode)법으로 계산한 결과 crystal field splitting <TEX>${\Delta}cr$</TEX>값이 0.1291 eV이며 spin-orbit <TEX>${\Delta}so$</TEX>값은 0.0248 eV임을 확인하였다. 10K일 때 광전류 봉우리들은 n = 1일때 <TEX>$A_1$</TEX>-, <TEX>$B_1$</TEX>-와 <TEX>$C_1$</TEX>-exciton 봉우리임을 알았다. A stoichiometric mixture of evaporating materials for <TEX>$CdIn_2S_4$</TEX> single crystal thin films was prepared from horizontal electric furnace. To obtain the single crystal thin films, <TEX>$CdIn_2S_4$</TEX> mixed crystal was deposited on thoroughly etched semi-insulating GaAs(100) substrate by the Hot Wall Epitaxy (HWE) system. The source and substrate temperatures were <TEX>$630^{\circ}C$</TEX> and <TEX>$420^{\circ}C$</TEX>, respectively. The crystalline structure of the single crystal thin films was investigated by the photoluminescence and double crystal X-ray diffraction (DCXD). The carrier density and mobility of <TEX>$CdIn_2S_4$</TEX> single crystal thin films measured with Hall effect by van der Pauw method are <TEX>$9.01{\times}10^{16}\;cm^{-3}$</TEX> and <TEX>$219\;cm^2/V{\cdot}s$</TEX> at 293 K, respectively. The temperature dependence of the energy band gap of the <TEX>$CdIn_2S_4$</TEX> obtained from the absorption spectra was well described by the Varshni's relation, <TEX>$E_g(T)=2.7116\;eV-(7.74{\times}10^{-4}\;eV)T^2/(T+434)$</TEX>. The crystal field and the spin-orbit splitting energies for the valence band of the <TEX>$CdIn_2S_4$</TEX> have been estimated to be 0.1291 eV and 0.0248 eV, respectively, by means of the photocurrent spectra and the Hopfield quasi cubic model. These results indicate that the splitting of the <TEX>${\Delta}so$</TEX> definitely exists in the <TEX>${\Gamma}5$</TEX> states of the valence band of the <TEX>$AgInS_2$</TEX>/GaAs epilayer. The three photocurrent peaks observed at 10K areascribed to the <TEX>$A_1$</TEX>-, <TEX>$B_1$</TEX>-, and C1-exciton peaks for n = 1.

The Characteristics of GaP Window Layer Grown by Indium-added Liquid Phase Epitaxy

The effects of added indium on the growth characteristics of GaP were systematically studied using conventional liquid phase epitaxy technique with Ga-rich GaP source melt. The GaP growth rate uniformly increase with the source melt of increasing indium addition against gallium solvent. These epilayers have mirror-like surface morphology examined by optical microscope except several grown films with large amount of indium addition meet a terrible interface. The surface morphologies examined by AFM showed the ripples in samples of R 0.05 and R 0.4 and distinct islands with elliptical base shape in the sample of R 0.7 (R-In ratio). The epitaxial layer with incorporation of indium addition during growth had good performance on the carrier concentrations and resistivity. The composition of compound semiconductor become to InGaP at higher amount of In addition to Ga was examined by double-crystal X-ray diffraction and the distribution of indium examined by SIMS also provided the evidences in sample of R 0.7 .

Photo-stimulated current spectroscopy and its application in detecting aluminum implantation-induced deep traps in GaN

In this work, a semi-insulating GaN film is obtained in the Al + implanted (by energy and dose: 500 keV and 10 14∼10 15 cm −2, respectively) area. Measurements of double crystal X-ray diffraction (XRD) rocking curve shows that the implanted samples still remain a good quality of crystallinity. This may identify that the vanishment of the band edge emission with phonon replicas is due to the ion implantation-induced deep traps located in the forbidden gap, but not due to the change of the crystal structure. In order to detect the position of the traps, we developed a new method, namely photo-stimulated current spectroscopy (PSCS) in our measurement. Three two-component deep traps located at 1.77 eV (with 1.90 and 1.77 eV components), 1.17 eV (1.24 and 1.16 eV components) and 0.88 eV (0.90 and 0.86 eV components) below the conduction band minimum were found in the annealed sample. The two components may be due to the different levels in one trap. It is expected that the PSCS is suitable for measuring the deep levels in all semi-insulating semiconductor films.

Ultrafast trapping times in ion implanted InP

As + and P+ implantation was performed on semi-insulating (SI) and p-type InP samples for the purpose of creating a material suitable for ultrafast optoelectronic applications. SI InP samples were implanted with a dose of 1×1016 cm−2 and p-type InP was implanted with doses between 1×1012 and 1×1016 cm−2. Subsequently, rapid thermal annealing at temperatures between 400 and 700 °C was performed for 30 sec. Hall-effect measurements, double-crystal x-ray diffraction, and time-resolved femtosecond differential reflectivity showed that, for the highest-annealing temperatures, the implanted SI InP samples exhibited high mobility, low resistivity, short response times, and minimal structural damage. Similar measurements on implanted p-type InP showed that the fast response time, high mobility, and good structural recovery could be retained while increasing the resistivity.

Determination of residual stress in thin films: a comparative study of X-ray topography versus laser curvature method

The residual stress in thin films has been determined by X-ray diffraction and laser scanning methods. The usual procedure is to measure the strain via lattice or physical curvature analysis and then to calculate the stress using continuum mechanics models. X-ray and laser techniques measure different physical quantities. In the former case, the curvature of crystal lattice planes is assessed while in the latter situation the curvature of physical surface of the sample is measured. In principle, these two methods should yield the same results. The current experiments use the latest two-dimensional X-ray double crystal diffraction topography (DCDT) and a laser scanning technique (LST) to determine the quantities of interest for a variety of thin films deposited on Si (1 0 0) wafers. The measurements by the two techniques were performed on the same samples, at the same time, under exactly identical conditions. For specimens where the residual stresses produce large curvatures of both types (lattice curvature and surface curvature), the results for DCDT and LST agree within the experimental error. When small to moderate curvatures are present, the two methods deviate to varying degrees. This deviation is of special significance in determining residual stress in nanometer-thickness films. Nevertheless, DCDT and LST generally yield similar results on differential curvatures, i.e. the stress induced curvature differentials. When proper consideration is taken for the inherent limits of each technique, both DCDT and LST can be used as valid procedures for stress measurement in thin film–substrate systems.

Epitaxial PbZr.52Ti.48O3 films on SrTiO3/(001)Si substrates deposited by sol–gel method

We report on the sol–gel deposition and characterization of high-quality, epitaxial films of PbZr.52Ti.48O3 (PZT) on (001)Si substrates, with a thickness range of 400 Å to 1 μm. The epitaxial growth of PZT on (001)Si is achieved using a thin template layer of SrTiO3, grown by molecular-beam epitaxy. The sol–gel PZT films have a typical surface roughness of 5 Å and exhibit well defined reflective high-energy electron diffraction patterns characteristic of smooth, epitaxial films. Using high-resolution transmission electron microscopy and double-crystal x-ray diffraction, we find that the PZT films are oriented with the c axis normal to the (001)Si plane and with the a axis lying along 〈110〉Si direction. Finally, we measure the electromechanical coupling coefficients and the surface acoustic wave velocities for our films as a function of thickness and compare our experimental data to previously published theoretical values for this system.