Indium phosphide based indium arsenide quantum dot infrared photodetectors

Despite the high detectivity that has been achieved in the state-of-the-art HgCdTe (MCT) discrete infrared photodetectors, a high performance large-area focal plane array (FPA) based on MCT is not available due to the uniformity problem. Taking advantage of modern crystal growth advancements, intersubband photodetectors based on III-V compound semiconductors such as quantum well infrared photodetectors (QWIPs) and quantum dot infrared photodetectors (QDIPs) emerge as the promising technologies to outperform the state-of-the-art MCT devices. Comparing QDIP to QWIP, the former has an important advantage of sensitivity to normal incident light. However, current experimental results of QDIPs lag behind the theoretical predictions. Besides, while most research is based on the GaAs-based QDIPs, very limited studies have been focused on InP-based QDIPs, which have great potential to generate high performance infrared detectors for their higher electron mobility and ease of achieving multilayer QD structures on InP substrates.; This thesis thoroughly discusses the design and molecular beam epitaxy (MBE) growth of multilayer InAs QDs grown on InP substrate for the fabrication of QDIPs. To realize this goal, achieving single layer QDs with high morphological and optical quality is the foremost objective of this study. The evolution of the surface morphology of InAs nanostructures grown on InGaAs/InP under various growth conditions was studied through atomic force microscopy imaging. It is observed that a thick InAs layer (9 monolayers) is necessary in forming QDs. However, varying other growth parameters alone cannot generate QDs with high morphological and optical quality. A novel technique of using the InGaAs surface structure modified superlattice as the matrix layer was developed to suppress quantum wire formation, thus forming uniform QDs from an InAs deposition as thin as 2.5 MLs. When an InAlGaAs matrix layer was used for InGaAs, it further improved the morphology of the InAs QDs, which displays a uniform QD size distribution and a strong room temperature photoluminescence.; To encounter the three-dimensional growth front and the strain accumulation during multilayer QD growth, a group-III stabilized surface was used to smooth out the three-dimensional growth front. A strain-balanced QD structure has been developed to solve the strain accumulation problem. Thus, a defect-free 50-layer strain-balanced InAs QD sample was achieved, demonstrating great potential for fabrication of high performance multilayer QD photodetectors.; Based on the developed QD growth techniques, photoconductive InAs/InAlGaAs/InP QDIPs grown on InP by MBE technique were presented. These devices demonstrated responses to normal incident photoexcitations in the 5-18-mum range. The QDIP device based on bound-to-bound transitions shows a peak responsivity of 113 mA/W and a detectivity of 1.8 x 10 9 cmHz1/2/W at 10 K for a 10-period QD heterostructure. The device based on bound-to-continuum transitions demonstrates an improved dark current characteristics and a better detectivity of 2.1 x 10 9 cmHz1/2/W.