Pawel Kaminski

Investigation of defect levels in semi-insulating materials by modulated and transient photocurrent: comparison of methods

High-resolution photoinduced transient spectroscopy and the modulated photocurrent technique are compared in terms of possible application to the investigation of defect levels in semi-insulating monocrystalline materials. After a description of the theoretical and experimental aspects, the advantages, drawbacks and limitations of each method are discussed. The two techniques complement each other and their potentialities are exemplified by the measurements of trap parameters in the same samples of semi-insulating Cr-doped and undoped GaAs. From these results we deduce a possible model for the properties of the Cr defect in GaAs.

High-Resolution Photoinduced Transient Spectroscopy of Electrically Active Iron-Related Defects in Electron Irradiated High-Resistivity Silicon

High-resolution photoinduced transient spectroscopy (HRPITS) has been employed to investigate iron-related point defects produced by electron irradiation in high-resistivity silicon. The measurements revealed 16 traps with activation energies ranging from 14 to 530 meV. From the comparison of results, obtained by the HRPITS and ESR measurements performed on the same samples, a trap positioned at Ev+500 meV was attributed to the iron-vacancy pair (Fei)V and that positioned at EV+530 meV to the vacancy complex with two iron atoms (Fei)2V. The former is found to be stable at 400°C, while the latter anneals out at this temperature similarly to the trap at EV+410 meV related to interstitial iron. As a result of the transformation of the (Fei)2V complex and reactions of the interstitial iron with native defects, new iron-related traps with activation energies of 85, 220 and 380 meV are formed.

Dielectric properties of semi-insulating silicon at microwave frequencies

The permittivity and dielectric loss tangent of high-purity silicon with semi-insulating properties achieved by the irradiation with 23-MeV protons have been measured at frequencies from 1 GHz to 15 GHz. The dielectric losses were separated from the conductor losses on the basis of the total loss tangent measurements versus frequency. The resistivity measurements of the material performed at radio frequencies (RF) by means of the capacitance spectroscopy method have shown the non-uniform resistivity distribution in the direction perpendicular to the surface of the semi-insulating wafer. The excellent agreement between the resistivity measurements results at RF and those obtained by using microwave methods have been achieved. It has been confirmed that high-purity, semi-insulating silicon is practically non-dispersive and possesses extremely low dielectric losses that are constant to within experimental errors in the frequency range from 1 GHz to 350 GHz. In this frequency range, the dielectric loss tangen...

Analysis of two-dimensional PITS spectra for characterization of defect centers in high resistivity materials

Deep states in semi-insulating Si are investigated by analyzing of two-dimensional Photo-Induced Transient Spectroscopy (PITS) spectra. The results exemplify new potentialities of the advanced computer programming technique.

Investigation of deep-level defects in semi-insulating GaAs and InP by analysis of photo-induced current transients

Abstract A new digital approach to PICTS technique was applied to study deep levels in undoped SI GaAs and Fe-doped InP. For SI Fe-doped InP, the 0.64-eV trap related to Fe2 + /Fe3 + acceptor level as well as the 0.53-eV trap attributed to a native defect, were observed. For SI undoped GaAs, three traps: T1 (0.58 eV), T2 (0.66 eV) and T3 (0.73 eV) assigned to the known centers EL3, HL9, and EL2, respectively, were resolved. The studies were completed by the electron spin resonance (ESR) measurements.

High Q-Factor Millimeter-Wave Silicon Resonators

Resonators made of high-resistivity silicon (HRS) have been manufactured, and their characteristics were measured at a frequency range from 20 to 50 GHz. To study the influence of the material resistivity on Q-factor values, two HRSs were used. The first one was as-grown high-purity floating zone (FZ) silicon with a resistivity of ~70 kQ · cm. The second was FZ silicon irradiated with high-energy protons. The resistivity of the irradiated silicon was essentially the same as that of intrinsic silicon with a resistivity of ~400 kQ · cm at room temperature. Several whispering gallery modes were identified and measured on disk shape samples made on both materials. At room temperature and at a frequency of 50 GHz, the Q-factor values for the resonators made of the as-grown and the irradiated silicon are up to 1.8 × 104 and up to 6 × 104, respectively.

Tailoring the Electrical Properties of Undoped GaP

The charge compensation in undoped GaP single crystals is investigated by modeling the Fermi level position for various concentrations of shallow and deep donors and acceptors. The model is based on the numerical solution of the charge neutrality equation and allows for calculating the Fermi energy in the temperature range of 1 –1000 K. The experimental studies of the electronic properties and concentrations of grown-in defect centers are performed by the high-resolution photoinduced transient spectroscopy (HRPITS). We show that at the shallow acceptor concentration below 1x1015 cm-3 and the concentration of deep-level defects ~3x1015 cm-3 obtaining undoped GaP with the semi-insulating (SI) properties is possible by substantial reducing the residual concentration of shallow donor impurities.

Compensating defect centres in semi-insulating 6H-SiC

Photoinduced transient spectroscopy (PITS) has been applied to study electronic properties of point defects associated with charge compensation in semi-insulating (SI) 6H-SiC substrates. The photocurrent relaxation waveforms were digitally recorded in a wide temperature range of 20–800 K and in order to extract the parameters of defect centres, a two-dimensional analysis of the waveforms as a function of time and temperature has been implemented. As a result, the processes of thermal emission of charge carriers from defect centres were seen on the spectral surface as the folds, whose ridgelines depicted the temperature dependences of emission rate for detected defect centres. The new approach was used to compare the defect levels in vanadium-doped and vanadium-free (undoped) SI 6H-SiC wafers.

Laplace transform photoinduced transient spectroscopy: a new powerful tool for defect characterization in semi-insulating materials

For the first time Laplace transform deep level transient spectroscopy is presented as a powerful tool for investigation of defect centers in high-resistivity materials. The potentialities of the new method are exemplified by the characterization of defect centers in high-resistivity neutron irradiated silicon and semi-insulating InP.© (2003) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Deep-level defects in semi-insulating LT MBE GaAs

High resolution photo induced transient spectroscopy has been utilized to study defect centers in semi-insulating molecular beam epitaxy GaAs grown at temperatures 300 and 400