Compound materials enable the production of advanced, easy-to-use power devices, ultra-high frequency radio devices and more. These emerging products become more and more prevalent in electric or hybrid cars for example, or in power management and distribution devices related to renewable energy sources. For reliable production, composition and defects, dopant concentration, electrical and optical qualities must be regularly monitored. Semilab offers several products for this purpose. Most products are non-contact and non-destructive, and in many cases, they reveal properties directly related to device characteristics or performance.
Spectral photoluminescence (PL) is a non-contact, non-destructive, spectroscopy-based measurement technique to probe the electronic structure of different materials. Spectral PL can be used to obtain information on the emission properties of different heterostructures (quality control) and/or crystal structure of the material.
Photoluminescence is a photon emission process that occurs during relaxation from electronic and/or localized (defects) excited states. Charge carriers can recombine through Shockley-Read-Hall (SRH) and radiative recombination simultaneously. The radiative recombination rate is proportional with the product of electron and hole concentrations. As the minority carrier density is decreased by the SRH recombination that takes place at defects and impurities, the radiative recombination is inversely proportional to defect density and impurity concentration. During radiative recombination, a photon is emitted, which can be detected by a spectrograph. This is the photoluminescence (PL) signal.
Semilab offers the spectral PL metrology possibility to characterize compound semiconductors from DUV to NIR spectral region (GaN, SiC, GaAs/InGaAs, GaP). Monitoring of Al-content of AlGaN alloys, PL wavelength dependence as a function of dopant concentration of GaN and GaAs materials, monitoring of single and multi-layer stacking faults of epi SiC layers are covered by our PL metrology tools. Furthermore, the combination of PL and other metrology units (for example Raman, spectral ellipsometry (SE), imaging spectroscopic reflectometry (iSR)) is possible for our medium and big sized platforms allowing the measurement of spectroscopic and thickness data from the same location.
The excitation laser(s) are focused on the sample with a spot size between 10-100 µm. The Semilab PL systems use multiple lasers that are coaxial and have achromatic optics to enable a wide range of applications. The light of the radiative recombination is emitted isotropically inside the sample, which is then collected by spectrographs working either in the visible or the near-infrared ranges. The optical system is designed in such a way that the excitation lasers are highly suppressed, thus the reflected laser light does not disturb the PL signal.
The dual spectrograph setup allows the user to cover a very wide range of samples with PL signal from the UV to the near-infrared spectrum without any need to mechanically reconfigure the system.
Our PL systems are computer-controlled equipments, suitable for recording, storing and displaying photoluminescence maps. Fundamental parameters of the PL spectra like wavelengths, intensities and full width half maximums (FWHM) are analysed in real time.
The Semilab PL systems are equipped with high accuracy detectors, very fast motion stages that enable the recording and analysis of PL maps with extremely high resolution. These maps allow a very precise characterization of the production line performance and provide a rapid feedback for process optimization.
Spectral Photoluminescence systems of Semilab provide
Offline (R&D) & Inline (Production) applications:
SPL-2100 is a non-contact, non-destructive, spectroscopy-based measurement system to probe the electronic structure of different materials.
Features and system specifications
SPL-2200/2500 is a non-contact, non-destructive, spectroscopy-based measurement system to probe the electronic structure of different materials.
Features and System specifications: