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Title: Physical properties of interband and interband cascade edge- and surface-emitting mid-infrared lasers
Author: Ikyo, Achakpa Barnabas
ISNI:       0000 0004 0132 8446
Awarding Body: University of Surrey
Current Institution: University of Surrey
Date of Award: 2011
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Physical properties of GalnAsSb-based type-I quantum well 2.3μm and 2.6μm edge emitting lasers are investigated using spontaneous emission and hydrostatic pressure techniques. Temperature dependence spontaneous emission analysis on GalnAsSb/AlGaAsSb (1.6%) compressively strained EEL emitting at 2.3pm shows that at least 81+-5% of the threshold current at room temperature is due to non-radiative recombination. It is also shown that Auger recombination (CHLH and/ or CHSH) is the dominating non-radiative process. It is also shown that non-pinning of the carrier density above threshold causes the external differential efficiency of these 2.3 μm to decrease. There is also evidence of defect related recombination. For the 2.6μm devices made of GalnAsSb/GaSb 1.7% compressively strained quantum well, at least 97+-2% of threshold at room temperature is due to non radiative recombination. It is also shown that Auger current is the dominant process. There is also evidence of hole leakage and defect current in the 2.6μm EELs. T0 analysis show evidence of optical loss process suspected to be IVBA occurring which may couple the effects of non-pinning of the carrier density above threshold to cause the decreasing external differential efficiency observed in the devices. Investigation of GalnAsSb/AlGaAsSb 2.3μm VCSELs shows that the gain peak and cavity mode are aligned at T~260+-10K. The analyses here suggest that for improved performance of the 2.3pm VCSEL, the gain peak should be shifted to higher energies by approximately 10meV. For the GalnAsSb/GaSb 2.6μm VCSEL, the gain peak- cavity mode alignment is estimated to be at higher temperature (T=330+-10K) while the temperature insensitive region is obtained at T~200+-20K. It is estimated that by shifting the gain peak to higher energies (by approximately 8meV), the temperature insensitive region can be shifted to room temperature. Spontaneous emission analysis on 5 stage “W” interband cascade lasers (ICLs)show that at least 93+-2% of threshold current is due to non-radiative recombination. Pressure dependence of threshold current at 100K, 200K and 293K suggest that Auger recombination is the dominant loss process and is significant even at low temperatures. Considering the complex valence band structure of the “W” ICLs, it is possible that the CHLH Auger process is occurring even though the CHSH and CHCC are theoretically shown to be supressed. It is also shown that non-pinning of the carrier density above threshold causes the differential efficiency of the “W” ICL to decrease but IVBA may also be partly responsible.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available