Momentum relaxation due to polar optical phonons in AlGaN/GaN heterostructures

Zhang, J.-Z.; Zhang, J-Z; Dyson, A.; Ridley, B. K.

Abstract

Using the dielectric continuum (DC) model, momentum relaxation rates are calculated for electrons confined in quasi-two-dimensional (quasi-2D) channels of AlGaN/GaN heterostructures. Particular attention is paid to the effects of half-space and interface modes on the momentum relaxation. The total momentum relaxation rates are compared with those evaluated by the three-dimensional phonon (3DP) model, and also with the Callen results for bulk GaN. In heterostructures with a wide channel (effective channel width >100 Å), the DC and 3DP models yield very close momentum relaxation rates. Only for narrow-channel heterostructures do interface phonons become important in momentum relaxation processes, and an abrupt threshold occurs for emission of interface as well as half-space phonons. For a 30-Å GaN channel, for instance, the 3DP model is found to underestimate rates just below the bulk phonon energy by 70% and overestimate rates just above the bulk phonon energy by 40% compared to the DC model. Owing to the rapid decrease in the electron-phonon interaction with the phonon wave vector, negative momentum relaxation rates are predicted for interface phonon absorption in usual GaN channels. The total rates remain positive due to the dominant half-space phonon scattering. The quasi-2D rates can have substantially higher peak values than the three-dimensional rates near the phonon emission threshold. Analytical expressions for momentum relaxation rates are obtained in the extreme quantum limits (i.e., the threshold emission and the near subband-bottom absorption). All the results are well explained in terms of electron and phonon densities of states.

Citation

Zhang, J., Zhang, J., Dyson, A., & Ridley, B. K. (2011). Momentum relaxation due to polar optical phonons in AlGaN/GaN heterostructures. Physical review B: Condensed matter and materials physics, 84(15), Article ARTN 155310. https://doi.org/10.1103/PhysRevB.84.155310

• Journal Article Type: Article
• Acceptance Date: Jul 5, 2011
• Online Publication Date: Oct 17, 2011
• Publication Date: Oct 17, 2011
• Deposit Date: Nov 13, 2014
• Publicly Available Date: Nov 13, 2014
• Journal: Physical review B
• Print ISSN: 1098-0121
• Electronic ISSN: 1550-235X
• Publisher: American Physical Society
• Peer Reviewed: Peer Reviewed
• Volume: 84
• Issue: 15
• Article Number: ARTN 155310
• DOI: https://doi.org/10.1103/PhysRevB.84.155310
• Keywords: Electronic, Optical and Magnetic Materials; Condensed Matter Physics
• Public URL: https://hull-repository.worktribe.com/output/466635
• Publisher URL: http://journals.aps.org/prb/abstract/10.1103/PhysRevB.84.155310
• Additional Information: Copy of article first published in Physical review B, 2011, v.84, issue 15