Gallium arsenide based MBE-grown quantum structures for near infrared wavelength applications
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The emission wavelength of a quantum well depends on the bandgap of quantum well and the barrier surrounding the well. Traditionally, the bandgap of the well is reduced by addition of indium and nitrogen to GaAs (GaInNAs alloys) on GaAs substrates or by addition of indium to GaAs (GaInAs alloys) on InP substrates to obtain emission wavelengths at 1.3 or 1.55 µm. However, the growth of these alloys is associated with numerous growth issues, such as plasma damage in GaInNAs/GaAs heterostructures and lack of suitable epitaxial mirrors for InP-based structures. A reduction in bandgap of barriers surrounding the quantum wells is another means to increase emission wavelength. This dissertation reports on the work done to investigate the influence of barrier on optical properties of quantum wells. A novel quantum structure using plasma assisted MBE – grown Ga1-xInxAs (x < 0.3) quantum wells with GaNyAs1-y (y < 0.05) barriers is studied to obtain near infrared emission wavelengths. The influence of Ga1-xInxAs (x < 0.2) matrix on MEE – grown Ga0.5In0.5As quantum dots on GaAs substrates is also studied to understand the influence of a barrier on the quantum structure. Relocating nitrogen from quantum well to the barrier and introducing a GaAs spacer at the barrier – to – well and well – to – barrier interfaces has helped in reducing the influence of plasma-damage on optical properties of the GaInAs quantum well.