Attend in person at ESB 1001!
Meeting ID: 835 9351 1974
Graduate Student Researcher, DenBaars Group
University of California, Santa Barbara
N-polar Indium nitride quantum dashes and quantum wires:
MOCVD growth and characterization
InN, which is normally utilized for InGaN-based visible and ultraviolet optoelectronics, has interesting electrical properties, including a low electron effective mass of 0.07m0, leading to the highest theoretical mobilities of the III-nitrides of up to 14,000 cm2 V-1 s-1 at 300 K and the highest electron saturation drift velocity of the III-nitrides. These properties make InN an intriguing choice for III-nitride electronic devices. However, its performance has fallen short of theoretical limits because of the challenges involved in achieving high quality epitaxial material due to its high lattice mismatch to available substrates (10% to GaN) and low growth temperature requirements, especially by metalorganic chemical vapor deposition (MOCVD).
MOCVD growth of N-polar InN on miscut substrates results in InN quantum dashes which can be capped with planarized GaN, enabling the demonstration of multi-layer InN dash structures. Multi-layer structures are difficult to achieve using the In-polar orientation, where taller dots form and the GaN cap layers follow the dot shape, resulting in three dimensional structures. In this work, the growth parameter space of MOCVD-grown horizontal N-polar InN quantum wires on GaN was investigated using morphological and electrical measurements. It was found that a low temperature of 540 °C with a narrow thickness window of 1 nm – 2 nm was required to form InN quantum wires rather than dashes. Fabricated InN wire samples were electrically conductive with sheet resistances of 10 – 26 kΩ/□ along the wire direction. InN wires could be capped with a thin layer of GaN while retaining electrical conduction. The results of this work demonstrate the possibility of control over the dimensionality of lower-dimensional InN epitaxial structures while establishing the performance limits of such structures on GaN.
HOST: Dr. Matthew Wong