This Small Business Innovation Research Phase I project, entitled "Integration of Langmuir- Blodgett quantum dot films into optoelectronic device heterostructures", will drive incorporation of colloidal semiconductor quantum dots (SQD) into inorganic semiconductor optoelectronic devices. Nanostructure plays a critical role in high efficiency operation of IIInitride light emitting diodes over a range from violet to blue-green. Dot Metrics Technologies has novel intellectual property to extend III-nitride LED color to the deep green through integration of II-VI SQD layers. Electroluminescent devices with low wall plug efficiency have been demonstrated by DMT and others. Drop casting and spin casting methods used so far to deposit SQD result in non-uniform layers of SQDs, degrading uniformity of vertical electronic transport through the heterostructures. In this project, standard Langmuir-Blodgett monolayer film deposition techniques will be employed to deposit single layers of SQD. In this way, SQD active layers will be on the order of the same thickness as quantum wells in III-nitride LEDs. Molecular beam epitaxy (MBE) will be used to encapsulate SQD to form device heterostructures, and light emitting diodes will be fabricated and tested. The broader impact of this project is significant. Deep green light, near the human eye response peak, is an essential component of "white light" and multicolor displays. Typically, deep green is generated through lossy phosphor down-conversion. This project will result in higher efficiency generation of deep green through direct electrical pumping of SQD. Resulting devices will be highly marketable; thus, the work will attract further funding from non-SBIR sources upon completion. Also, direct electrical control of deep green allows better control of subjective color quality, resulting in higher quality lighting and displays, and also energy savings. Integration of SQD with traditional semiconductor epitaxy is itself a marketable process, potentially applicable to other types of optoelectronic devices such as detectors or solar cells. DMT has executed four other SBIR projects to date, and while no products have yet been commercialized, significant technical progress has been made as evidenced by the numerous publications associated with this work
