Surface passivation of infrared laser diode and photodiode

III-V semiconductor compounds are interesting candidates for a variety of optoelectronic applications. However, these semiconductors suffer from poor surface properties leading to device degradation. As the surface is chemically unstable, it leads to formation of native oxide on the surface with time and exposure to atmosphere. The oxide semiconductor interface has high density of interface states, dangling bonds and defects, which lead to facet degradation in case of laser diodes and surface leakage current in case of photodiodes. Thus treatment of surface by removal of oxide and passivation is imperative to improve the performance of the device.; The goal of this research was to study the effect of passivation on two important optoelectronic devices namely, high power infrared laser diodes and infrared photo detectors. A method for estimating the temperature at the facet of a 940 nm Al-free ridge-waveguide InGaAsP-GaAs high power laser diode has been developed. This is based on correlating the change in cladding layer photoluminescence wavelength due to the operation of the device to the wavelength change by external heating. Facet temperatures of unpassivated, unpumped and passivated devices were compared to the bulk temperature. The results indicate that the facet temperature of unpassivated devices were 20°C--30°C hotter than the device bulk temperature whereas the facets of passivated devices were only 10°C--15°C hotter than the bulk in the initial 50 hours of burn-in. Power measurements indicate a power drop of 3--5% in devices with unpassivated facets in the initial 50 hours, while no such degradation occurs for passivated facets. Thus oxidation is the dominant degradation mechanism and hence cleaning and passivation of the facets is imperative in obtaining stable high power laser diodes.; The second part of this research addressed the passivation of GaSb mesa etched photo diode. Deposition of a few monolayers of sulfur on the wafer surface has been found to passivate the surface dangling bonds. However, the bonds formed by this ultra-thin layer of sulfur are weak and thus with exposure to light and oxygen the effect of passivation is lost. Thus, research and development of suitable capping layers to avoid the disintegration of Ga-S and Sb-S bonds is necessary. Prior capping layer schemes such as, SiN x and SiO2 caps have been unsuccessful due to the surface degradation during plasma or sputter deposition of the cap layers. (Abstract shortened by UMI.)...