Weak localization and dimensional crossover in compositionally graded AlxGa1−xN
Abstract
The interaction between the itinerant carriers, lattice dynamics, and defects is a problem of long-standing fundamental interest for developing quantum theory of transport. Here, we study this interaction in the compositionally and strain-graded AlGaN heterostructures grown on AlN substrates. The results provide direct evidence that a dimensional crossover (2D–3D) occurs with increasing temperature as the dephasing scattering events reduce the coherence length. These heterostructures show a robust polarization-induced 3D electron gas and a metallic-like behavior down to liquid helium temperature. Using magnetoresistance measurements, we analyze the evolution of the interaction between charge carriers, lattice dynamics, and defects as a function of temperature. A negative longitudinal magnetoresistance emerges at low temperatures, in line with the theory of weak localization. A weak localization fit to near zero-field magneto-conductance indicates a coherence length that is larger than the elastic mean free path and film thickness (lφ>t>lel), suggesting a 2D weak localization in a three-dimensional electron gas. Our observations allow for a clear and detailed picture of two distinct localization mechanisms that affect carrier transport at low temperature.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Feb 22, 2021
- Source ID
- 10.1063/5.0042098
Entities
People
- Abdullah Al Shafe
- Athby Al-tawhid
- Baxter Moody
- Kaveh Ahadi
- Pegah Bagheri
- Pramod Reddy
- Ramón Collazo
- Seiji Mita
- Yan Guan
- Zlatko Sitar
Organizations
- Air Force Office of Scientific Research
- Division of Electrical, Communications & Cyber Systems
- North Carolina State University