Theoretical Design and Material Growth of Type-II Antimonide-based Superlattices for Infrared Detection and Imaging.

摘要

The goal of this PhD thesis is to investigate quantum properties of the superlattice system, design appropriate device architectures and experimentally fabricate infrared detectors which can outperform currently existing devices.;In parallel, efforts in material growth using molecular beam epitaxy (MBE) have resulted in higher material quality and vastly improved growth conditions of III-V compounds as compared to previous work. Superlattices as thick as 15mum were realized without growth defects or dislocations, narrow X-ray diffraction peaks and small surface roughness. Many ternary and quaternary layers such as InAsSb, AlAsSb, GaAlAsSb were routinely used in new design architectures to enhance the electrical performance of the devices.;Advances in theoretical calculations and material growth have allowed this work to continue with comprehensive studies of photodetector device architectures. Fundamental parameters affecting the performance of infrared detectors were investigated. We have experimentally pointed out the difference in the collection of photocurrent generated in the n-type and p-type regions. By forcing the device's active region to have an appropriate p-doped concentration, and by assuring long diffusion carrier lengths with high material quality, the quantum efficiency of Type-II superlattice photodiodes have been demonstrated in excess 50% in front side illumination configuration and 75% in back side illumination configuration. In an attempt to optimize the electrical performance, basic mechanisms of the dark current have been thoroughly analyzed. By intentionally doping the active region, the diffusion and generation-recombination currents were reduced until they were overwhelmed by the tunneling current. The device performance was then further enhanced due to the suppression of the tunneling current using the hetero-design of the M-structure superlattice. This optimization scheme can be repeated iteratively to lower all bulk-components of the dark current until the device performance is dominated by the surface component. The results of this thesis' work show that the design and material quality of bulk Type-II-superlattice is thus not a limiting factor for optimal device performance.;Further employment of the M-structure superlattice has resulted in a novel device architecture called the pMp design. This novel device is a hybrid between conventional photoconductive and photovoltaic detectors. Profiting from the advantages of its parents' configurations, the pMp design has shown numerous advantageous for infrared detections such as low generation-recombination current, suppressed tunneling current, and reduced surface leakage while keeping high optical efficiency of the detectors based on long-diffusion-length minority electrons. This design can also be used as a simple architecture for bias-selectable dual color detection which is proven to mitigate the difficulties of both the material growth and the device fabrication.;In addition to improving the performance of single element detectors, this work also contributed to the successful demonstration of focal plane arrays at the Center for Quantum Devices. For the first time, the polarity of Type-II photodiodes has been matched with the requirement of commercially available Read Out Integrated Circuits (ROICs) through the realization of n-type InAsSb This polarity matching has significantly improved the imaging quality because it allows the bias and carrier types to be correctly utilized. Furthermore, attempts on 3" in diameter superlattice growth wafer were made, which resulted in excellent material uniformity across the whole wafer. Finally, targetting "color" imaging, different sophisticated architectures for dual spectral detection were demonstrated, in which each channel exhibited similar performance as that of single element detectors. (Abstract shortened by UMI.)