Young-Gu Ju - Academia.edu (original) (raw)
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Papers by Young-Gu Ju
Optics Express, 2006
Electrostatic discharge(ESD) damage is known as a major source affecting the lifetime of oxide VC... more Electrostatic discharge(ESD) damage is known as a major source affecting the lifetime of oxide VCSEL. We investigated how ESD damage threshold voltage depends on the size, thickness, and composition of the oxide aperture by measuring the change of output power and reverse leakage current after ESD. ESD damage threshold voltage increased with the size of the oxide aperture, regardless of the thickness and the composition of the oxide aperture. However, damaged devices with thinner oxide layers showed relatively longer lifetime in the reliability test. The reliability data also showed that the VCSELs exposed to ESD have steeper power declines in reliability test than normal devices. This may be due to the defects formed in the active medium by ESD.
Applied Physics Letters, 1997
We report that the 780 nm quantum well vertical-cavity surface-emitting lasers ͑VCSELs͒ grown on ... more We report that the 780 nm quantum well vertical-cavity surface-emitting lasers ͑VCSELs͒ grown on a 2°off misoriented ͑001͒ substrate toward ͑111͒A exhibit a high polarization suppression ratio over a few hundred. The main polarization is always along the ͓Ϫ110͔ direction for all the lasers over the entire operating currents. To understand the physical origin of this polarization selectivity, the gain/loss difference between two competing polarization modes in VCSELs is investigated by measuring the subthreshold spectral linewidth. The obtained modal gain/loss difference is about 3.0 cm Ϫ1 , which is sufficiently large for polarization stabilization and amounts to 4% of the threshold modal gain. Comparison with the subthreshold measurement and previous theoretical work shows significant discrepancy, which implies the possibility of other polarization selection mechanisms inducing such large gain/loss differences in 780 nm quantum wells grown on a misoriented substrate. In addition, it is found that the 780 nm VCSEL made of a bulk active medium grown on a misoriented substrate also shows a high polarization selectivity as quantum well lasers.
Optics Express, 2006
Electrostatic discharge(ESD) damage is known as a major source affecting the lifetime of oxide VC... more Electrostatic discharge(ESD) damage is known as a major source affecting the lifetime of oxide VCSEL. We investigated how ESD damage threshold voltage depends on the size, thickness, and composition of the oxide aperture by measuring the change of output power and reverse leakage current after ESD. ESD damage threshold voltage increased with the size of the oxide aperture, regardless of the thickness and the composition of the oxide aperture. However, damaged devices with thinner oxide layers showed relatively longer lifetime in the reliability test. The reliability data also showed that the VCSELs exposed to ESD have steeper power declines in reliability test than normal devices. This may be due to the defects formed in the active medium by ESD.
Applied Physics Letters, 1997
We report that the 780 nm quantum well vertical-cavity surface-emitting lasers ͑VCSELs͒ grown on ... more We report that the 780 nm quantum well vertical-cavity surface-emitting lasers ͑VCSELs͒ grown on a 2°off misoriented ͑001͒ substrate toward ͑111͒A exhibit a high polarization suppression ratio over a few hundred. The main polarization is always along the ͓Ϫ110͔ direction for all the lasers over the entire operating currents. To understand the physical origin of this polarization selectivity, the gain/loss difference between two competing polarization modes in VCSELs is investigated by measuring the subthreshold spectral linewidth. The obtained modal gain/loss difference is about 3.0 cm Ϫ1 , which is sufficiently large for polarization stabilization and amounts to 4% of the threshold modal gain. Comparison with the subthreshold measurement and previous theoretical work shows significant discrepancy, which implies the possibility of other polarization selection mechanisms inducing such large gain/loss differences in 780 nm quantum wells grown on a misoriented substrate. In addition, it is found that the 780 nm VCSEL made of a bulk active medium grown on a misoriented substrate also shows a high polarization selectivity as quantum well lasers.