2DEGs formed in AlN/GaN HEMT structures with AlN grown at low temperature
Caroline E. Reilly, Nirupam Hatui, Thomas E. Mates, Shuji Nakamura, Steven P. DenBaars, S. Keller
Abstract
Integration of nitrides with other material systems has recently become of interest due to the high performance of GaN-based high-electron mobility transistors. However, the elevated growth temperatures often used to grow high quality AlN pose challenges toward metalorganic chemical vapor deposition (MOCVD) on temperature sensitive substrates such as processed wafers. In this work, the growth of AlN was conducted at temperatures below 550 °C via MOCVD using a flow-modulated epitaxy scheme, and their morphological, compositional, and electronic properties of these films were investigated. Sheet charges up to 2.1 × 1013 cm−2 and mobilities on the order of 400 cm2/V s were measured for two dimensional electron gases, which formed at the interface between the low temperature grown AlN layers and the semi-insulating GaN base layers deposited at high temperatures. Despite their low growth temperatures, nominally pure AlN barrier layers exhibited measurable unintentional gallium incorporation adjacent to the GaN interface. The result sets the stage for the integration of nitride-based electronics via epitaxy-based schemes on temperature sensitive substrates.