Raman analysis of phonon lifetimes in AlN and GaN of wurtzite structure

Abstract

Raman analyses of the lifetimes of phonons in GaN and AlN crystallites of wurtzite structure are presented. In order to ensure the accuracy of the measurement of the phonon lifetimes, an experimental procedure to eliminate the broadening due to the finite slit width was performed. The lifetime analyses indicate that the phonon lifetimes in AlN as well as in GaN fall into two main time regimes: a relatively long time of the E 2 1 mode and much shorter times of the E 2 2 , E1͑TO͒, and A1͑TO͒ modes. The lifetimes of the E 2 1 , E 2 2 , E1͑TO͒, A1͑TO͒, and A1͑LO͒ modes of an high-quality AlN crystallite are 4.4, 0.83, 0.91, 0.76, and 0.45 ps, respectively. Moreover, the lifetime of the A1͑LO͒ mode found in this study is consistent with the current phonondecay model of that mode in wurtzite structure materials. The lifetimes of E 2 1 , E 2 2 , E1͑TO͒, and A1͑TO͒ of a GaN crystallite were found to be 10.1, 1.4, 0.95, and 0.46 ps, respectively. The A1͑LO͒ mode in the GaN was not observed and its absence is attributed to plasmon damping. The lifetime shortening due to impurities was also studied: the lifetimes of the Raman modes of an AlN crystallite, which contains about two orders of magnitude more Si and C impurities relative to the concentration of the high-quality crystallite were found to be 50% shorter. ͓S0163-1829͑99͒04419-7͔

Low-loss, infrared and terahertz nanophotonics using surface phonon polaritons

“…Here, we have used a first principles technique [159] to calculate and examine the nearzone-center optic phonon (TO and LO) intrinsic lifetimes, for the various polar dielectric materials given in Table 3. The calculated room-temperature bulk optical phonon lifetime reported here are in general accord with the available experimental data [56,60,63,[145][146][147][148][149][150][151][152][153][154][155], and fall in the range of 0.5 ps to 9 ns, orders of magnitude larger than SPP lifetimes. For instance, lifetimes between 0.6-0.8 ps and 1.4-1.9 ps were reported for wurtzite AlN [154] for the LO and TO phonon lifetimes, respectively, which compares quite favorably to our corresponding calculations of 0.88 and 2.01 ps.…”

“…Optic phonon lifetimes have been determined from Raman scattering techniques for a number of materials (e.g., see Refs. [59,60,63,[145][146][147][148][149][150][151][152][153][154][155]), and first principles density functional theoretical methods have been developed and applied to calculate phonon dispersions and lifetimes without adjustable parameters (e.g., see Refs. [134,141] and [156][157][158]).…”

Spin-resolved spectra of Shiba multiplets from Mn impurities inMgB2

“…In the following, we illustrate our results on the specific case of Mn-doped MgB 2 , but we wish to emphasize that much of our discussions carry over to other systems as well, 10 and that our conclusions are rather general. There are several reasons to choose the Mn-MgB 2 system.…”

Phonon Dynamics and Lifetimes of Aln and Gan Crystallites

“…The first part of this paper presents a study of the LO and TO quasi modes in AlN crystallite which originate from the interaction of phonons belonging to the A1 and E1 symmetry groups; the study focuses on the mode-selection rules and mode-frequency calculations as well as on the Raman technique which enables the observation of the quasi-modes [3]. The second part of the paper focuses on Raman analyses of the lifetimes of phonons in GaN and AlN crystallites [4]. The lifetime analyses indicate that the phonon lifetimes in AlN as well as in GaN fall into two main time regimes: a relatively long time of the low energy E2 mode, which will be referred to as E2(low), and the much shorter times of the high energy E2 mode (referred to as E2(high)) and the E1(TO), A1(TO), and A1(LO) modes.…”