Intraband absorption in self-assembled Ge-doped GaN/AlN nanowire heterostructures

M. Beeler (1, 2) , P. Hille (3) , J. Schörmann (3) , J. Teubert (3) , M. de la Mata (4) , J. Arbiol (4, 5) , M. Eickhoff (3) , E. Monroy (1, 2)

1 SP2M - UMR 9002 - Service de Physique des Matériaux et Microstructures
2 NPSC - Nanophysique et Semiconducteurs
3 Physikalisches Institut [Gießen]
4 Institut de Ciència de Materials de Barcelona (ICMAB-CSIC)
5 ICREA - Institució Catalana de Recerca i Estudis Avançats = Catalan Institution for Research and Advanced Studies

: We report the observation of transverse-magnetic-polarized infrared absorption assigned to the s−p$_z$ in self-assembled GaN nanowires (NWs). The s−p$_z$ absorption line experiences a blue shift with increasing ND Ge concentration and a red shift with increasing ND thickness. The experimental results in terms of interband and intraband spectroscopy are compared to theoretical calculations of the band diagram and electronic structure of GaN/AlN heterostructured NWs, accounting for their three-dimensional strain distribution and the presence of surface states. From the theoretical analysis, we conclude that the formation of an AlN shell during the heterostructure growth applies a uniaxial compressive strain which blue shifts the interband optical transitions but has little influence on the intraband transitions. The presence of surface states with density levels expected for m-GaN plane charge-deplete the base of the NWs but is insufficient to screen the polarization-induced internal electric field in the heterostructures. Simulations show that the free-carrier screening of the polarization-induced internal electric field in the NDs is critical to predicting the photoluminescence behavior. The intraband transitions, on the other hand, are blue-shifted due to many-body effects, namely, the exchange interaction and depolarization shift, which exceed the red shift induced by carrier screening

Domaines: Sciences de l'ingénieur [physics]; Matière Condensée [cond-mat]; Science des matériaux [cond-mat.mtrl-sci]

M. Beeler, P. Hille, J. Schörmann, J. Teubert, M. de la Mata, et al.. Intraband absorption in self-assembled Ge-doped GaN/AlN nanowire heterostructures. Nano Letters, 2014, 14 (3), pp.1665-1673. ⟨10.1021/nl5002247⟩. ⟨hal-02119215⟩