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Title: Development of AlGaInSb multi quantum-well light emitting diodes in the 3-5 μm spectral range
Author: Reza, Manuel
ISNI:       0000 0004 8503 0187
Awarding Body: University of Glasgow
Current Institution: University of Glasgow
Date of Award: 2019
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Antimonide alloys are promising semiconductors for the realisation of optoelectronic devices in the mid-infrared range from 3 to 5 μm. The interest in this wavelength range stems from the presence of strong and unique absorption fingerprints of various gas species, making it ideal for remote sensing. Compared to the traditional thermal components used in Non-Dispersive Infrared (NDIR) carbon dioxide (CO2) sensors, antimonide semiconductor technology offers a very interesting alternative for the development of CO2 gas sensors with lower power consumption, faster response time, and higher selectivity to the gas species. The main goal of this Ph.D. project, supported by an EPSRC Industrial CASE Studentship with Gas Sensing Solutions (GSS) Ltd. was to decrease the power consumption and increase the sensitivity of the carbon dioxide gas sensors currently produced by GSS, limited by the low output power and wall-plug efficiency of the Light Emitting Diode (LED) device. After identifying the intrinsic limitations that cause poor device internal quantum efficiency, a novel LED Multi-Quantum Wells (MQWs) active region design comprising aluminium gallium indium antimonide (AlGaInSb) alloys was investigated. This epilayer design demonstrated a peak emission wavelength of 4.3 μm, corresponding to the CO2 peak absorption fingerprint, with more than six times brightness and four times electrical power efficiency compared to the AlInSb LED design used by GSS. Alongside the MQW design, a thorough optimisation of the whole fabrication process was also carried out with a focus on the development of a robust dry etching process for antimonide alloys, which resulted in smooth surfaces, uniform etch rates for a large range of different alloy compositions and controllable angles of the etched sidewall slope profiles. The latter feature is of great interest for the future development of LED and photodiode devices because 40°-sloped sidewalls offer a two-fold improvement in light extraction or collection efficiency and a far better directivity when mounted on a flip-chip configuration.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
Keywords: QC Physics ; TK Electrical engineering. Electronics Nuclear engineering