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Title: Carrier recombination in dilute nitride based near infrared semiconductor lasers
Author: McConville, Daniel
Awarding Body: University of Surrey
Current Institution: University of Surrey
Date of Award: 2007
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This thesis describes and quantifies the roles of the different carrier recombination processes within near infrared GaInNAs single quantum well laser devices. An initial review of the published literature relating to GaInNAs highlighted a number of areas where investigation of the material system would be interesting, including changing the nitrogen concentration, the barrier material, the incorporated strain and the growth technique. We find that at 1.3mum, at room temperature, the threshold current of MBE grown devices is composed of 70% Auger recombination, 25% monomolecular recombination and 5% radiative recombination, and at 1.5mum, 61% Auger recombination, 31% monomolecular recombination and 8% radiative recombination. In absolute terms Auger is the most significant current path over the entire wavelength range. This dominance of Auger recombination was also found to be responsible for the poor temperature stability of these devices, with the Auger recombination component typically having a T0 ~50K. Calculations of the threshold carrier density along with a break-down of the threshold current were used to evaluate the recombination coefficients; these were found to be A = 4x108 (s-1), B - 3x10-11 (cm3s-1) and C = 6x10-29 (cm6s-1) at 1.3mum, and A = 8x108 (s-1), B = 6x10 -11 (cm3s-1) and C = 1.2x10-28 (cm6s-1) at 1.5mum. These values are comparable to those of InGaAsP and AlGaInAs. Furthermore, these investigations suggest that carrier leakage is negligible in these devices. Hydrostatic pressure techniques were used to study the effect of changing the band gap on the recombination processes occurring within the devices; this highlighted the importance of the band anti crossing interaction between the conduction band edge and the nitrogen level in GaInNAs devices where it was seen that a longer wavelengths this interaction appears to be weaker. Replacing GaAs barriers with GaNAs barriers leads to a ~ 15% reduction in the magnitude of the monomolecular current present, indicating that this should be a useful method of optimising the growth of GaInNAs. An investigation into the effect of strain incorporated within the quantum well of the ~1.5mum devices highlighted the possibility of its use to reduce the threshold carrier density and thus the Auger current within these devices. Since this work was based on single quantum well devices it shows that the GaInNAs material system is a very promising alternative to conventional InGaAsP and AlGaInAs devices which rely upon multiple quantum wells.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available