High-temperature deep-level transient spectroscopy system for defect studies in wide-bandgap semiconductors.

Full investigation of deep defect states and impurities in wide-bandgap materials by employing commercial transient capacitance spectroscopy is a challenge, demanding very high temperatures. Therefore, a high-temperature deep-level transient spectroscopy (HT-DLTS) system was developed for measurements up to 1100 K. The upper limit of the temperature range allows for the study of deep defects and trap centers in the bandgap, deeper than previously reported by DLTS characterization in any material. Performance of the system was tested by carrying out measurements on the well-known intrinsic defects in n-type 4H-SiC in the temperature range 300-950 K. Experimental observations performed on 4H-SiC Schottky diodes were in good agreement with the literature. However, the DLTS measurements were restricted by the operation and quality of the electrodes.

Detection of H2O and CO2 with distributed feedback diode lasers: measurement of broadening coefficients and assessment of the accuracy levels for volcanic monitoring.

We reproduced the chemical-physical conditions of fumarolic emission at Phlaegrean Fields, Pozzuoli, Italy, and we measured the CO(2) and H(2)O concentrations using an absorption spectrometer based on two distributed feedback laser diodes at wavelengths of 1.578 and 1.393 microm. We discuss the accuracy levels of the different methods used. Furthermore, we measured the broadening coefficients for H(2)O (self-broadening, 28.2 +/- 0.6 MHz/Torr; CO(2) broadening, 6.0 +/- 0.4 MHz/Torr) and CO(2) (self-broadening, 3.2 +/- 0.1 MHz/Torr; H(2)O broadening, 4.0 +/- 0.1 MHz/Torr). Using the present data, we evaluated a minimum detectable variation of 9% for H(2)O and 1% for CO(2).