M. Pawłowski

Error analysis and design of the Nutt time-interval digitiser with picosecond resolution

Several sources of errors related to the Nutt time-interval digitiser are discussed, including the quantisation process, time jitter, non-linearity of time stretchers and phase noise of the reference clock. A model of the total measurement uncertainty is formulated. The authors also describe the main circuitry and test results of a microprocessor-controlled digitiser which has been developed to achieve a negligible quantisation error (1 ps resolution) and 1 ms range.

A method for autocalibration of the interpolation time interval digitiser with picosecond resolution

A calibration method is described which allows precise determination of the stretch factors of the time stretchers used in the interpolation time interval digitiser with 1 ps incremental resolution. The method is based on analysis of statistical phenomena related to time jitter close to the threshold level of the phase detectors contained in the interpolators. The bias error inherent in the method is analysed and compensation of that error is discussed. A detailed description of a microprocessor procedure to perform automatic calibration is given. The usefulness of the method is proved by numerical examples and experimental results.

Low-jitter wide-range integrated time interval/delay generator based on combination of period counting and capacitor charging

We present the design, operation, and test results of a new time interval/delay generator that provides the resolution of 0.3 ps, jitter below 10 ps (rms), and wide delay range of 10 s. The wide range has been achieved by counting periods of a reference clock while the high resolution and low jitter have been obtained through the two-time use of inner interpolation. This interpolation, based on charging of a single capacitor, provides both the precise external trigger synchronization and accurate generation of residual time interval. A combination of both processes virtually eliminates triggering indeterminacy. The jitter between the trigger and output is below 1 ps, which ensures a high performance delay. The generator is integrated in a single application specific integrated circuit chip using a standard cost-effective 0.35 μm CMOS process.

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.

Effect of temperature errors on accuracy of deep traps parameters obtained from transient measurements

The procedure of determination of deep traps parameters by both deep level transient capacitance spectroscopy (DLTS) and photoinduced transient spectroscopy (PITS) is based on Arrhenius plot illustrating the dependence of thermal emission rates as a function of temperature. In this article the effect of temperature measurement inaccuracy on the values of activation energy and capture cross- section obtained from the Arrhenius plot is analyzed. The inaccurate values of temperature involve both a change of slope and shift of the Arrhenius plots along vertical axis. The practical application of the analysis is exemplified by estimation of the temperature errors responsible for the shift of Arrhenius plots related to the center A in irradiated silicon. This article addresses the issue of temperature errors in DLTS and PITS measurements from the metrological point of view.

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.

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