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Title: Gain studies of dilute nitride semiconductor materials
Author: Palmer, David J.
ISNI:       0000 0004 2748 8253
Awarding Body: Cardiff University
Current Institution: Cardiff University
Date of Award: 2006
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Due to the increased use of optical fibre communications, there is much interest in semiconductor lasers operating between 1.3 and 1.6pm and grown on GaAs substrates. One approach used to achieve this is the dilute nitride material, InGaAsN. In this work, the segmented contact method was used to study dilute nitride quantum well laser active regions designed to operate around 1.3pm. The net modal absorption, net modal gain and spontaneous emission rate spectra were measured for samples with quantum well nitrogen contents of 0%, 0.5% and 0.8% and GaAs barriers. A sample with 0.5% quantum well nitrogen content but larger bandgap GaAsP barriers was also examined. By defining and measuring the inversion factor, the spontaneous emission rate spectra were calibrated and the overall internal efficiencies of the samples calculated. The modal absorption and gain data provide the first experimental evidence for the matrix element reducing as nitrogen content increases. The measured maximum absorption predicts a matrix element relative to a nitrogen free quantum well of 0.58 and 0.67 for 0.5% and 0.8% nitrogen respectively. The measured overall internal efficiency was found to decrease dramatically with increasing nitrogen content, falling from approximately 15% to 5% between 0% and 0.8% nitrogen when measured at 300K. Comparisons between samples with different quantum well barrier heights showed an increase in the measured maximum absorption of a factor 1.28 and an increase in the overall internal efficiency of approximately a factor 1.15 when the barrier height was increased. No barrier emission was observed in the spontaneous emission rate spectra measured from the top of these samples. However, the calculated occupation of the GaAsP barrier sample was less than 3% of the sample with GaAs barriers, suggesting that a reduction in leakage current could explain the improved efficiency.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available