UC Santa Barbara

An important semiconductor material system, the III-nitrides have a significant place in lighting, optoelectronics, and electronics applications. The most common nitrides are InN, GaN, AlN, and alloys thereof. One primary growth method for the nitrides is metalorganic chemical vapor deposition (MOCVD), an epitaxial growth technique commonly used in the semiconductor industry, where standard growth temperatures for high quality GaN and AlN are above 1000 °C. These high growth temperatures create problems when integrating GaN and AlN with temperature sensitive materials such as InN, which sublimes around 550 °C, or semi-processed wafers. This work will focus on the growth of III-nitride materials via low temperature (LT) MOCVD towards applications such as infrared InN LEDs and integration of GaN electronics with silicon.LT growth can be particularly challenging due to decreased mobility of surface adatoms as the temperature is lowered, leading to poorer morphology. In addition, increased im- purity incorporation occurs at reduced growth temperatures. To counteract these issues, pulsed growth schemes such as flow modulation epitaxy (FME) have been employed in the growth of GaN and AlN. Optimization of LT FME GaN growth will be discussed with step-flow growth achieved at 550 °C. The ability to grow high quality GaN at low temperatures can enable a variety of devices which rely on GaN as basis for their epitaxial structures. The growth of LT FME AlN was conducted and AlN/GaN heterostructures were grown. Electrical properties such as the existence and properties of two-dimensional electron gases (2DEGs) were studied, of interest for high-electron mobility transistors (HEMTs). Turning then to optoelectronics applications, the use of InN quantum dots (QDs) for infrared light-emitting devices will be considered. InN and InGaN QDs were grown and variations were made to their composition, growth temperature, nominal thickness, and growth plane. Uncapped and capped QDs were studied, with QD structures and infrared photoluminescence maintained after capping with LT GaN. Full LED structures with InN QD active regions were made possible by employing LT FME GaN growth. These results lay the foundation for the use of LT nitride MOCVD for these and other temperature sensitive applications.