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Material based limitations on charge transport in GaAs based LEDs structures at low temperatures
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School of Science |
Master's thesis
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en
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69
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Light Emitting Diodes (LEDs) based on gallium arsenide (GaAs) are widely used in optoelectronic applications due to their direct bandgap, high efficiency, and good radiative recombination properties. Recently, there has been increased interest in GaAs LEDs for emerging applications beyond lighting, particularly in cryogenic data transmission and thermophotonic cooling applications. This study investigates the material-based limitations on charge transport in GaAs based LED structures for low temperature applications, motivated by the potential use of GaAs in cryogenic systems such as data transmission in quantum computing. This thesis focussed on three key elements potentially affecting the charge transport: (i)electrical contacts, (ii)semiconductor material and (iii)barrier at GaAs/GaInP heterostructure. Contact resistivity was evaluated using transmission line model (TLM) methods over a range from 5 K to room temperature. The temperature dependencies of charge carrier properties of the semiconductor material and barrier height of the heterostructure were studied over a temperature range from 120 K to 350 K.
Results showed that, for the selected fabrication flow and materials, the contact resistivity and material parameters would be unlikely to prevent low temperature applications. However, an unexpected large barrier height between n- GaAs and n- GaInP, as compared to one estimated from band discontinuity, suggested that both n- and p-type interfaces could affect the efficiency of final devices at temperatures below room temperature. This is in partial contrast with original expectations and may call for finding alternative strategies to fully remove the effects of barrier at low temperature.
These findings highlight key factors affecting the performance of GaAs based LEDs under low temperature conditions and generally support their feasibility for cryogenic applications.
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Supervisor
Halme, JanneThesis advisor
Oksanen, JaniRadevici, Ivan