The Center offers modern equipment to determine the characteristics of micro- and nano-dimensional multilayered heterostructures intended for different kinds of micro- and optoelectronic devices using the dynamic secondary ion mass spectrometry (IMS-4f Secondary Ion Microprobe,САМЕСА, France) and Auger electron and photoemission spectroscopy (Multitecnique PHI-5500 Spectrometer, PHYSICAL ELECTRONICS, US). This equipment provides the detailed control over materials during the development of epitaxial processes of a nanoheterostructures growth. Moreover, the techniques used in the Center have been certified by the Federal Agency for Technical Regulation and Metrology, e.g., the technique of obtaining the data on depth distribution of electrically active dopants such as Si and Mg in GaN material.
1. MULTITECHNIQUE PHI 5500 (US) is the system for X-ray photoelectron spectroscopy (XPS), electronic spectroscopy for chemical analysis (ESCA), Auger electron spectroscopy (AES), and electron energy loss spectroscopy (EELS)
1.1 XPS, ESCA
In X-ray photoelectron spectroscopy a surface of the studied sample is irradiated by a beam of X-rays with energy of 1.2 or 1.5 keV and the energy spectrum of secondary electrons that escape to vacuum (outer photoemissive effect) is analyzed. XPS is used to obtain the data on elemental composition, chemical bonds of atoms in a near surface region, the thickness of which is equal to the depth of information. In combination with layer-by-layer dry etching of a sample by ions of inert gases XPS allows one to determine the depth distribution of elements. The structure of a material valence band can also be determined by XPS.
Main applications of XPS: elemental and chemical analysis nonorganic and organic materials, analysis of electronic structure, 2D pictures of elemental and chemical composition of a surface, depth profiling of elemental and chemical compositions. XPS is used in material science of structural and electronic materials as well as in studies of catalysis, adsorption, phenomena at heterophase interfaces, and carbon-containing nonorganic and organic materials and structures including polymers and biological substances.
1.2 AES
In Auger electron microscopy a plane surface of the studied sample is irradiated by a focused beam of primary electrons with energy of 3-25 keV and the energy spectrum of secondary electrons that escape to vacuum is analyzed. AES is used to determine elemental composition of a near surface region and 2D surface distribution of elemental composition. In combination with layer-to-layer dry etching by ions of inert gases AES can determine the depth distribution of elements in a material.
Main applications of AES: elemental analysis, 2D pictures of surface elemental analysis, depth profile analysis of elemental and chemical composition. AES is widely used in material science of structural and electronic materials and structures, in studies of heterophase interface phenomena.
1.3 EELS (reflection type)
EELS as well as AES consists in studying the energy spectrum of secondary electrons escaped into vacuum from a sample by the focused beam of primary electrons with energy of 0.1–3 keV. EELS allows one to obtain the valuable information about electronic structure of a target and its depth structure, and in combination with dry etching of the studied sample, – depth profiles of the desired characteristics of the studied structure.
Main applications of EELS: analysis of electronic structure of a sample and, in some cases, elemental analysis; nondestructive study of a near surface regions at depths up to some tens nanometers. EELS is used to study various metallic and semiconductor heterostructures.
CAMECA IMS4F is the ion microprobe for dynamic secondary ion mass spectrometry (D-SIMS)
2.1 D-SIMS
In D-SIMS the surface of a sample is induced by bombardment of the focused beam of fast primary electrons, usually O2+ or Cs+. D-SIMS allows one to determine elemental and impurity composition of the surface to a depth of few nanometers and 2D surface distribution of elemental composition. In combination with dry etching of a sample, D-SIMS allows one to determine distribution of main elements and dopants over thickness and to study 3D distribution of main elements through the sample.
Main applications of D-SIMS: local elemental and isotopic analysis; analysis of depth profiles of main and doping elements through samples that are inhomogeneous with respect to thickness, e.g., in heterostructures; study of 2D and 3D atomic distributions in complex heterophase structures (structural materials, structures for micro- and optoelectronics, etc.).
General view of a secondary ion microprobe, САМЕСА IMS-4f (France)
The Optical Measurement Complex was registered in the State Register of Measurement Facilities on July 9, 2012. The active checking is dated April 6, 2012.
1. OL 770-LED High-speed LED Test and Measurement System Configured for Source Spectral Analysis of LEDs”
” (Optronic Laboratories Inc., US) with two UV/VIZ and VIZ/IR spectrometers that overlap a wavelength range from UV to near IR: 250-1100 nm. The system is equipped with two integral spheres with a diameter of 6 and 18 inches, precise power supply for continuous and pulsed measurements as well as a set of replaceable optical units including a goniometric system and chamber to measure axial radiant intensity, replaceable filters to expand a diapason, etc. The developed software allows one to measure and calculate the main characteristics of LEDs for a few seconds.
Typical measurements include:Precise control over the housing and ambient temperature as well as input current and voltage is provided during the measurements. Current scanning can be implemented and the corresponding current dependences of luminous flux, spectral distribution, and other parameters can be obtained.
The replaceable units in the composition of the System allow one to measure the optical characteristics of materials used in the design of LEDs and light sources (semiconductor layers, contact and reflective coatings, polymer coatings): spectral and angular dependences of transmittance, reflectance, and scattering coefficient as well as their integral values in a solid angle of 2 sr.
The System is characterized by the certificates of calibration in accordance with NIST standards; the measurement techniques have been certified in the VNIIOFI.
General view of the System and interface for control and measurement data display.
2. IS-LI™ Luminous Intensity Measurement System (Radiant Imaging Inc., US) for control of spatial distributions of luminous intensity and emission color.
The special-purpose equipment for express-control over the spatial characteristics of emission of, first of all, LEDs and diode lasers. The main components of the optical measurement circuit are a hemisphere illuminated by the analyzed light source, optical system constructing a CCD array image of the illuminated hemisphere, system of filters to determine chromaticity coordinates (color temperature). The software can calculate the angular distribution of luminous intensity, chromaticity coordinates, and color temperature for an angle of 2 sr. The advantage over goniometric systems for measurement of the spatial distribution of light is the absence of mechanical units. The equipment allows one to obtain a comprehensive, for an angle of 2 sr, spatial distribution of luminous intensity, chromaticity coordinates, and color temperature, which is especially urgent for testing large lots of products, revealing statistical distributions, etc. The technique has been certified in the VNIIOFI.
General view of IS-LI™ Luminous Intensity Measurement System and data display interface
3. OL 750-M-D, OL 750D Automated Spectroradiometer and Accessories for optical measurement with VIS-NIR wavelength
(Optronic Laboratories, Inc., US). Full options include a double monochromator with a high resolution of 0.05 nm, two silicon photodetectors with a sensitivity as high as 10-12 A, a set of optical attachments and standards to measure absolute values of absorption coefficient, mirror and diffuse reflectance, scattering coefficients as well as their angular distributions and integral values in the spectral range of 250-1500 nm, from middle UV to near IR. The equipment is intended to study optical parameters of photovoltaic and light emitting semiconductor devices as well as optical materials (epitaxial heterostructures, substrates, contact, insulating, reflective, immersion coatings) used in the technology of optoelectronic devices.
General view of OL 750-M-D OL 750D Automated Spectroradiometer and Accessories for optical measurement with VIS-NIR wavelength”
4.The measurement system for control over electrical and optical characteristics of LEDs over a wide temperature range is based on CCS-450 Standard Optical Closed-cycle Refrigerator Systems (Janis Research Company Inc, США) and Spectrometer Avaspec 2048 spectroradiometer (Avantes BV, Netherlands).
The main components of the system are a helium closed-cycle refrigerator, thermostatically controlled holder with an optical window, temperature controller, and pumping system. The equipment allows one to carry out highly accurate measurements of temperature coefficients of forward voltage, peak and dominant wavelength, external quantum efficiency, and other temperature dependences. The accuracy of thermostating is 0.5 K; the temperature range is 10-500 K.
General view of the probe head of the CCS-450 Standard Optical Closed-cycle Refrigerator Systems in combination with Avaspec 2048 spectrometer and temperature dependences of spectrum for AlInGaN LEDs in the temperature range of 50-420 K.
1. Thermal tester T3Ster (MicRed Ltd., Hungary) is intended for measurements of thermal resistances of semiconductor devices and integral units.
T3Ster is the generally recognized equipment for control over thermal resistance among the leading producers of semiconductor devices and integrated circuit components including LEDs and LED units such as GE Lumination, Samsung, etc. The action is based on the measurements of transient temperature dependent characteristics (e.g, LED forward voltage) as a response to the stepwise action (powerful current pulse). The equipment provides a means to determine the forward voltage across p-n junction at a time resolution of few microseconds after terminating the heated pulse and to calculate the total thermal resistance of a device and the resistance of separate links of a thermal circuit with a high accuracy of fractions of K/W. This parameter is among the important characteristics of high-power and solid-state light sources both at the stage of development and at determining the operational conditions. Full options include 4-channel basic unit, thermostat (working range of 5-900°C), current power supply and current amplifier (booster), and preamplifier for a thermocouple. The general view of the complex and example of the curve to determine thermal resistances of elements of LEDs and total thermal resistance of a device are shown below.
2. Thermal Imaging Complex: SVIT IR imager and UTK-1 IR thermal imaging microscope (Institute of Semiconductor Physics of the Siberian Branch of RAS, Russia)
The mapping of temperature fields over the area of a separate LED chip and LED modules is of a great practical importance for the development of devices as well as when choosing the acceptable operational conditions.
For this purpose, the IR thermal imaging method implemented in two versions, – infrared imager for large objects (matrices, modules, units) and thermal imaging microscope for separate chips, is used in the Center. The devices are based on the hybrid microcircuit chip of 128x128 InAs photodetector array with steps of elements of 50 µm and sensitivity in the wavelength range of 2.5 3.1 µm. the objects with dimensions from tens µm to few mm can be studied in the IR-microscope when using the replaceable lenses. The reached temperature resolution is ~ 1 K for objects with e temperature in the range of 300-450 K.
