Intersubband Absorptions in Doped and Undoped GaN/AIN Quantum Wells at Telecommunication Wavelengths Grown on Sapphire a
- PDF / 340,896 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 78 Downloads / 207 Views
Y4.5.1
Intersubband Absorptions in Doped and Undoped GaN/AlN Quantum Wells at Telecommunication Wavelengths Grown on Sapphire and 6H-SiC Substrates A. Helman1, M. Tchernycheva1, A. Lusson1, E. Warde1, F. H. Julien1, E. Monroy2, F. Fossard2, Le Si Dang2, B. Daudin1 1 Institut d’Electronique Fondamentale, UMR 8622 CNRS, Bât.220, Université Paris-Sud, 91405 Orsay, France 2 CEA/CNRS Research Group "Nanophysique et semiconducteurs ", DRFMC/SPMM, CEA/Grenoble, 17 rue des Martyrs, 38054 Grenoble cedex 9, France ABSTRACT In this paper we present experimental and theoretical study of intersubband transitions at telecommunication wavelengths in GaN/AlN hexagonal-phase quantum wells grown by molecular beam epitaxy on sapphire substrates. Crossed structural and photoluminescence experiments show that strong in-plane carrier localization occurs due to thickness fluctuations at GaN/AlN interfaces. Fourier transform infrared spectroscopy and photo-induced absorption spectroscopy performed on doped and undoped samples reveal a systematic blue-shift of the e1e2 transitions with doping due to many body interactions. A good agreement is achieved between experiments and self-consistent Schrödinger-Poisson calculations. INTRODUCTION Group-III nitride heterostructures are receiving new interest because of applications to optoelectronic devices at telecommunication wavelengths. One necessary condition for tuning intersubband transitions (IST) at short infrared wavelengths is to make use of semiconductor heterostructures with large band offset. One of the most promising candidates is the GaN/AlN quantum wells (QWs) system with the 1.8 eV potential discontinuity in the conduction band. Intersubband absorptions at 1.3-1.55 µm have already been observed by several groups in highly doped GaN/Al(Ga)N QWs grown by molecular beam epitaxy [1,2]. Due to the enhanced electron LO-phonon interaction in these structures the absorption recovery time is found to be subpicosecond, offering prospects for the development of ultrafast devices such as modulators and switches operating in the 0.1-1Tbit/second regime [3,4]. A GaN/AlN based quantum well infrared photodetector has also been reported [5]. In this work we investigate intersubband transitions in doped and non-intentionally doped GaN/AlN QWs grown on sapphire and 6H-SiC substrates. We show that doping induces a significant blue-shift of the intersubband transition energy due to exchange interaction. Strong in-plane carrier localization in the QWs due to monolayer fluctuations at the interfaces is demonstrated by combining room-temperature photoluminescence and structural characterizations, namely: Ruherford Back-scattering (RBS), X-ray diffraction and highresolution transmission electron microscopy (HRTEM). Good agreement between simulations and experiments is achieved in terms of intersubband transition energies for both doped and undoped quantum wells.
Y4.5.2
EXPERIMENTAL RESULTS A series of non-intentionally doped and Si-doped GaN/AlN quantum wells was grown by rfmolecular beam epitaxy (MBE) u
Data Loading...
