Details

Autor(en) / Beteiligte

• Beeler, M
• Hille, P
• Schörmann, J
• Teubert, J
• de la Mata, M
• Arbiol, J
• Eickhoff, M
• Monroy, E

Titel

Intraband Absorption in Self-Assembled Ge-Doped GaN/AlN Nanowire Heterostructures

Ist Teil von

• Nano letters, 2014-03, Vol.14 (3), p.1665-1673

Ort / Verlag

United States: American Chemical Society

Erscheinungsjahr

2014

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• We report the observation of transverse-magnetic-polarized infrared absorption assigned to the s–p z intraband transition in Ge-doped GaN/AlN nanodisks (NDs) 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.