On the Processing of InAsSb/GaSb photodiodes for infrared detection
- Authors: Odendaal, Vicky
- Date: 2008
- Subjects: Gallium arsenide semiconductors , Photovoltaic cells , Infrared detectors , Gas-detectors
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10523 , http://hdl.handle.net/10948/980 , Gallium arsenide semiconductors , Photovoltaic cells , Infrared detectors , Gas-detectors
- Description: The objective of this dissertation is the development of the necessary processing steps needed to manufacture infrared photodiodes on InAs1-xSbx material. Preliminary surface preparation steps were performed on both InAs and InSb material, thus covering both possible extremes of the antimony mole fraction. The first experiments endeavoured to characterise the effect of several possible etchants with regards to etch rate, repeatability, limitations for photolithographic patterning and the resultant surface roughness. The etchants investigated include a lactic acid based etchant, a sulphuric acid based etchant, an acetic acid based etchant, an ammonium based etchant, a hydrochloric acid based etchant as well as an organic rinse procedure. These cleaning and etching steps were evaluated at several temperatures. Measurements were performed on an Alpha Step stylus profiler as well as an atomic force microscope. Metal-insulator-semiconductor capacitor devices were manufactured, on both InAs and InSb material, in order to investigate the effects of the above-mentioned etchants combined with surface passivation techniques in terms of surface state densities. Capacitance-versus-bias voltage measurements were done to determine the resultant surface state densities and to compare these to the surface state density of an untreated reference sample. The surface passivation techniques included KOH, Na2S as well as (NH4)2S anodisation. Auger electron spectroscopy measurements were done on InAs and InSb material in order to examine possible surface contamination due to the etchants as well as combinations of these etching and anodisation procedures. The extent of surface coverage by contaminants as well as by the intrinsic elements was measured. The results of the cleaning and etching as well as the surface passivation studies were used to manufacture photovoltaic infrared diodes on an MOCVD (metal oxide chemical vapour deposition) grown p-InAs0.91Sb0.09/i- InAs0.91Sb0.09/n-GaSb structure. Current-versus-voltage and electro-optical measurements were performed on the these diodes in order to evaluate the effect of sulphuric acid based etching combined with KOH, Na2S or (NH4)2S anodisation on the detector performance. The results of surface passivated structures were compared to those of an unpassivated reference detector.
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- Date Issued: 2008
Handheld infrared CO2 gas detector
- Authors: Coetzee, George
- Date: 2000
- Subjects: Gas-detectors , Infrared detectors , Water quality -- Measurement
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:10807 , http://hdl.handle.net/10948/28 , Gas-detectors , Infrared detectors , Water quality -- Measurement
- Description: A handheld InfraRed (IR) Carbon Dioxide (CO2) gas detector was developed and used to carry out a study of water and urine samples in South Africa. The details of the model and the results of the study are discussed here. The overseas markets are not geared for the current South African conditions. Use is made of components that can be obtained locally. Imported components are very expensive and should an imported model be damaged, it has to be returned overseas to be repaired. As an illustration of this technology it was decided to perform research in water technology and then develope a handheld Infrared CO2 gas detector based prototype which would: highlight the benefits of using handheld IR CO2 gas detectors; be built locally; be powered by a 12 Volt supply; be very easy to maintain; and be cost effective. Experimental results on the accuracy and stability of the instrument formed part of this study. The IR CO2 Gas detector that was developed was used throughout the project as a prototype and testing vehicle for numerous designs. It proved to be superior to the current imported commercial instruments in terms of size, cost effectiveness and user friendliness. A further advantage of the instrument is its robustness.
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- Date Issued: 2000