气相外延GaN的拉曼散射

测量了在蓝宝石衬底上气相外延生长GaN的拉曼散射谱.除观察到已被确认的两个E2,一个A1(TO)和一个E1(TO)声于振动以外,在734±3cm-1处观察到一个散射峰且从实验上确认其为GaN的纵向光学声子模E1(LO).而且发现其强度与外延层晶体质量密切相关.A1(TO)和高频E2散射峰相对强度变化显示不同生长条件引起的外延层质量的变化.

RAMAN SCATTERING IN GaN GROWN BY VPE

Ⅲ-Ⅴ compound GaN has the Wurtzite crystal structure1] and belongs to symmetry group Vβγ For GaN, group theory predicts the following lattice phonons: A1 branch in which the Raman-active phonon is polarized in the z direction and which is infrared active also, and E1 branch in which the phonon polarized in the x, y plane can be observed in both infrared and Raman experiments, two E2 branches which are Raman active and two silent B1 modes2,3]. The A1 and E1 modes can be split into longitudinal (LO) and transverse (TO) components by the macroscopic electric field associated with the longitudinal phonon.Volia Lemos et al. E]have observed three Raman active optical phonon modes E2, A1(TO) and E1 (TO) in GaN epitaxy layer grown by vapor phase epitaxy (VPE) on sapphire substrate, No E1 (LO)mode was. observed in Raman scattering experiment previously4,5].The present work shows a Raman scattering experimental result in un-doped N-GaN samples grown on (0001) oriented sapphire substrate by VPE. An Ar+ laser was used as the excitation source.