Title Low frequency noise spectroscopy of nir lds (gaasbi,gaas,algaas) with parabolic and rectangular quantum wells /
Translation of Title Infraraudonosios srities lazerinių diodų su stačiakampėmis ir parabolinėmis kvantinėmis duobėmis triukšminė spektroskopija.
Authors Pinkrah, Richard
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Pages 49
Keywords [eng] reliability, generation and recombination noise, parabolic quantum wells, rectangular quantum wells, traps, noise spectral density, fluctuations Lorentzian spectrum, cross-correlation,
Abstract [eng] A comprehensive investigation of low-frequency noise characteristics of GaAs and GaAsBi based infrared laser diodes with parabolic and rectangular quantum wells were carried out. The aim of the investigation was to characterize the performance and quality of the lasers, to clear up noise origins in their structures. The investigated laser diodes were grown by molecular beam epitaxy. Measured characteristics include current-voltage characteristics and light output power (operating characteristic), low-frequency (10 Hz – 20 kHz) optical and electrical noise properties, and cross-correlation factor between optical and electrical fluctuations. Measurements were carried out at room temperature and in temperature range from 88 K to 300 K for PQW lasers. Current-voltage characteristic of the investigated laser diodes do not deviate far from the ideal behavior: the non-ideality factor of current-voltage characteristic is between 1 and 2. The flowing current mainly consists of diffusion and generation and recombination current components. In low frequency noise characteristics, 1/f noise and generation and recombination fluctuations with Lorentzian spectrum are manifested. Presence of 1/f noise is caused by the superposition processes of generation and recombination of charge carrier. These generation and recombination carriers’ centers are formed by different defects, dislocations, and imperfections in the active region of the laser diode structure. Electrical noise intensity for GaAsBi laser diode is very high as compared with GaAs rectangular and parabolic quantum well lasers due to larger number of defects caused by introduction of bismuth. Cross-correlation factor between optical and electrical fluctuations shows a high positive correlation of optical and electrical, what indicates that there are defects in the active region of investigated laser diodes which control current flow through the active region. Noise spectra at different temperatures were modeled and fitted by superposition of thermal noise, 1/f^α, 1/f and two Lorentzian components. The activation energy of observed two generation and recombination processes was evaluated and obtained 16.0 meV and 20.4 meV. Results showed that low frequency noise characteristics of the investigated laser diodes do not depend on the quantum well profile (rectangular or parabolic), but noise intensity is larger for GaAsBi based devices.
Dissertation Institution Vilniaus universitetas.
Type Master thesis
Language English
Publication date 2023