Figure 1: X-ray diffraction setup

Equipment

The X’Pert Pro diffractometer is a triple X-ray diffraction system. The X-ray beam produced by a Cu source is filtered by a hybrid 4-bounce monochromator working either in line or point focus, to filter the Kα1 (1.54 Å) line at low divergence (δθ=12″ with Ge 220 configuration). The diffracted beam can be recorded either in double-crystal configuration or using a three-bounce monochromator (3rd axis) before detection by a proportional detector. A dedicated sample holder allows grazing incidence diffraction experiments. This system is PC controlled and experimental results can be compared with simulations using the EPITAXY™ software. It is used for non-destructive control of samples, with diameter up to 100 mm.

Experiments

The applications are strongly linked to III-V semiconductor epitaxy for:

• alloy layer composition and thickness
• epitaxial layers lattice matching to the substrate
• superlattice interface quality
• thin layer strain determination
• relaxation rate and tilt of thick mismatched layers

Example: analysis of thin epitaxial Sb-based layers grown on GaAs substrate

Thanks to the high electron mobility of InAs and InSb, their small band gaps and their strong spin-orbit coupling,  ‘6.1 Å’ materials are very appealing for a number of applications in high-frequency microelectronics, mid-infrared optoelectronics and quantum technology. However, these materials suffer from the lack of lattice-matched, semi-insulating substrate, and metamorphic growth on GaAs or InP is often used for practical applications. In this case, numerous studies show strain relaxation of Sb-based III-V semiconductors grown on GaAs occurs via the formation of a Lomer dislocation array at the substrate /epilayer interface leading to a nearly fully relaxed layer. Nevertheless the threading dislocation density in the top layers remains rather high, strongly depending on the initial stages of the relaxation process. That is why we have investigated the relaxation of thin Sb-based layers and characterized their in-plane relaxation by grazing-incidence X-ray diffraction. On the spectra in figure 2, the angular spacing between the (220) reflexion of the GaAs substrate and that of the epilayer gives access to the in-plane lattice relaxation.

Figure 2: Grazing incidence X-ray diffraction spectra recorded after the growth of 16 monolayers AlSb or AlInSb on GaAs.

The micro-photoluminescence set-up is built around a LabRAM HR confocal system from Horiba Jobin-Yvon. It allows micro-luminescence measurements on low to large band gap materials, from low to

room temperature It is also used for Raman spectroscopy. Here are the main characteristics :

•  0.473 µm laser source
•  f=800 mm monochromator
•  CCD camera detection (0.3-1.06 µm)
• InGaAs monocanal detectors, cooled or not (0.9 to 2.2 µm)
• liquid nitrogen cooled InSb monocanal detector (1 to 5.5 µm)
• closed-cycle cryostat for microscopy Cryo Ind. (12 to 300 K)

The micro-photoluminescence set-up (where the cryostat is seen front left, on its micro-positionning table).

Close-view of the microscope cryostat and coupling with the LabRAM HR.

Example of Raman measurements: integrated intensity ratio map of CVD graphene after transfer on SiO2/Si (top), and Raman spectra of the circled area (bottom) (from Deokar et al., Carbon (2015) 89, 82).

Detail of the six probe assembly.

The HL 5500 PC system allows Hall effect measurements at room temperature, at liquid nitrogen temperature (77K) or by heating up to 600°C under controlled atmosphere. Six probes are used to contact the van der Pauw geometry or Hall bar samples so as to determine the sheet resistance of the layers. The sheet carrier density and their mobility are measured by Hall effect with a 0.32 Tesla permanent magnetic field.

Main applications:

– calibration of doping, n type and p type

– residual doping determination

– properties of two dimensional electron gas in HEMT structures

– …

The Hall effect set-up.

Equipment

The surface analysis system is connected to 2 molecular beam epitaxy chambers under ultra-high vacuum and to an introduction chamber, which allows the analysis of any sample. Based on a 5600 Physical Electronics system, the set-up has been adapted to work on 3-inch MBE sample holders. The main parts are:

• sample manipulator with 3 translations and 2 rotations (polar and azimuth)
• 150 mm radius hemispherical analyser
• X-ray dual anode Zr(2042eV)/Mg(1254 eV)
• monochromatic X-ray source Al (1487 eV)
• 8 keV electron gun with a 20 µm minimum spot size
• 5 keV ion gun
• He I (21.2 eV) and He II (40.8 eV) UV lamp
• neutraliser electron gun
• Low Energy Electron Diffractometer (LEED)
• In XPS experiments, the ultimate resolution is 0.45 eV, measured as the FWHM of the Ag 3d5/2 core level line.

In XPS experiments, the ultimate resolution is 0.45 eV, measured as the FWHM of the Ag 3d5/2 core level line.

Figure 1: General views of the ESCA system

Experiments

The know-how developed around the IEMN ESCA system concerns:

• the MBE grown III-V semiconductor surfaces and interfaces
• the characterization of process steps during device fabrication
• the grafting of organic layers

Moreover, this system is available for any kind of analysis from outside the laboratory.

Example: ESCA analysis of InGaAs surface after ALD oxide deposition

IEMN has an important activity in the semiconductor processing for the fabrication of opto and micro-electronic devices. In this context, XPS is used to characterize various processing steps, such as etching, annealing…….For instance, one such study has concerned the characterization of the ALD oxide deposition on InGaAs for the fabrication of III-V MOS structures by the IEMN “Anode” group. Figure 2 shows the As3d and Ga3d/In4d XPS core level lines recorded in non-optimized conditions, showing important InGaAs oxidization. On the contrary, in optimized conditions (figure 3), the XPS spectra do not reveal any oxide components on the InGaAs surface.

Figure 2: As3d (left) and Ga3d/In4d (right) XPS spectra recorded after ALD oxide deposition on InGaAs in non-optimized conditions. The InGaAs surface is heavily oxidized.

Figure 3: As3d (left) and Ga3d/In4d (right) XPS spectra recorded after ALD oxide deposition on InGaAs in optimized conditions. Oxide related XPS peaks have disappeared.

Thermogravimetric Analysis coupled with Mass spectrometry (TG/MS)

TG/MS Analysis is used to study the thermal behavior of any material (polymers, organic or inorganic, liquid or solid, film, fibers, powder, monolith) while exposed to heating and gas environment. Samples can be treated under various atmospheres. 

Figure 1: Thermogravimetry coupled with mass spectrometry apparatus

Gas environment available:

Inert atmosphere: (He, N₂, Ar,)
Oxidizing atmosphere: (2% O₂ in He, 20%O₂ in He)
Reducing atmosphere: diluted hydrogen (3% H₂ in Argon), and NH₃
Humid atmosphere: Inert and oxidizing atmospheres
Instrumentation includes 2 different systems:

• NETZSCH STA 449 F1- covers a temperature ranging from 25 to 1500°C
• NETZSCH STA 409- covers a temperature ranging up to 2000°C.

The two TGA systems are coupled with Quadrupole mass spectrometry (QMS) analysis. Line (capillary-type interface) connecting the TGA to MS can be heated to 300°C.

Figure 2: TG/MS: Thermal decomposition of hybrid organic-inorganic polymer in helium at 10°C/min

Specifications

Sample required

5-30 mg is the minimum mass required for sample analysis.
Samples should be non-explosive and non-corrosive.

Figure 3: Differential calorimeter (up to 600°C) Brand: Setaram-France

Differential Scanning Calorimetry (DSC)

DSC provides a convenient method of measuring heat capacities and enthalpy changes. Commercial instruments provide a recorder output of the constant-pressure heat capacity,(Cp) as a function of temperature.

DSC method can be used for the analysis of energetic effects such as:

• Melting / crystallization behaviour
• Solid-solid transitions
• Polymorphism
• Glass transitions
• Cross-linking reactions
• heat capacity measurements

Contact details

Dr D. Hourlier
Institut d’Electronique, de Microélectronique et de Nanotechnologie
IEMN UMR 8520, Avenue Henri Poincare, BP 60069 F-59652 Villeneuve d’Ascq Cedex-France
Room 133/135
+33 (0)3 20 19 78 36
djamila.hourlier@iemn.univ-lille1.fr