Abstract
GaAsBi is a suitable and very attractive material system to be used as an active layer in laser diodes (LDs). To understand the performance and the reliability of such devices and also for further laser diode improvements, the origin of noise sources should be clarified. A detailed study of near-infrared 1.09 μm wavelength GaAsBi type-I laser diodes using the low-frequency noise spectroscopy in a temperature range of (180–300) K is presented. Different types of voltage fluctuation spectral density dependencies on the forward current far below the lasing threshold have been observed. According to this, investigated samples have been classified into two groups and two equivalent noise circuits with the corresponding voltage noise sources are presented. Calculations on the voltage spectral density of the electrical noise and current-voltage characteristic approximations have been performed and the results are consistent with the experimental data. The analysis showed that one group of LDs is characterized by 1/fα-type electrical fluctuations with one steep electrical bump in the electrical noise dependence on forward current, and the origin of these fluctuations is the surface leakage channel. The LDs of the other group have two bumps in the electrical noise dependence on current where the first bump is determined by overall LD defectiveness and the second bump by Bi-related defects in the active area of LD with characteristic Lorentzian-type fluctuations having the activation energy of (0.16–0.18) eV.
Highlights
Bismuth containing GaAs (GaAs1-x Bix ) is a novel and very promising material system for optoelectronic devices, especially in fiber optic communication laser diodes (LDs) operating in the (1.3–1.5) μm wavelength region due to numerous advantages [1,2]
We report a comprehensive investigation of 1.09 μm type-I GaAsBi laser diodes through the low-frequency noise characteristics at forward bias
LDs, there is a strong relation between the electrical noise and current–voltage characteristics [17,22], e.g., leakage channel existence is usually followed by an increased low-frequency electrical e.g., leakage channel existence is usually followed by an increased low-frequency electrical fluctuations’ level [23]
Summary
Bismuth containing GaAs (GaAs1-x Bix ) is a novel and very promising material system for optoelectronic devices, especially in fiber optic communication laser diodes (LDs) operating in the (1.3–1.5) μm wavelength region due to numerous advantages [1,2]. For relatively high Bi composition (x > 10%), the spin-orbit splitting energy (∆so ) becomes larger than the band gap, which lets us expect the suppression of Auger recombination and inter-valence band absorption processes [1,3] This factor is the most important for bismide alloy application as active layers in telecommunication laser diodes [1]. The obtained noise characteristics contain information about physical processes that more or less influence semiconductor laser operation at lasing and overall device reliability The benefit of such a testing method is very important especially for multimode Fabry–Perot LDs—the sample is protected from damage of its internal structure caused by high flowing current through the specimen, and the noise component, generated due to the mode hopping effect, is not recorded as the LD operates in the subthreshold region. The aim of this work is to determine the noise sources, to identify their possible origin and to propose equivalent circuits of the investigated devices based on LDs current-voltage and electrical noise characteristics
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