Laser Power and Temperature Dependent Photoluminescence Characteristics of Annealed GaInNAs/GaAs Quantum Well
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Laser Power and Temperature Dependent Photoluminescence Characteristics of Annealed GaInNAs/GaAs Quantum Well Ng Tien Khee1,2, Yoon Soon Fatt1,2, Fan Weijun1 1
School of Electrical and Electronic Engineering (Block S1) Nanyang Technological University Nanyang Avenue, Singapore 639798. 2
Singapore-Massachusetts Institute of Technology (MIT) Alliance, Nanyang Technological University, Nanyang Avenue, Singapore 639798.
ABSTRACT Photoluminescence (PL) of annealed GaInNAs quantum well (QW) with varying temperature and laser excitation intensity is measured to understand the low temperature PL properties of annealed 6 nm GaInNAs QW. The measurements show that localization effect still exist in the QW even after annealing. This effect is characterized by an activation energy of 11 meV below the e1 state, which is obtained from fitting the integrated PL intensity vs. temperature curve with a single-activation-energy (SAE) model. This center is suggested to be related to the main localization center below the e1 state that could be resulted by N or In compositional fluctuation even after annealing.
INTRODUCTION Although GaInNAs-based laser [1] grown on GaAs provides both low cost and robust substrate advantages compared to lasers grown on InP, the fundamental studies of the GaInNAs QW PL mechanisms are still lacking. One of the issues concerns the fast quenching of the annealed GaInNAs QW at room temperature even though its 4.5 K PL efficiency increases after annealing [2]. Such characteristic is undesirable for current 1.3 µm or 1.55 µm high-speed optical communication systems that require optical devices operating at room temperature. It is therefore important to study the carrier dynamics of the GaInNAs QW. This issue can be studied and explained by PL measurements. In this investigation, a double QW structure was grown by a solid source molecular beam epitaxy (SSMBE) system, which allows efficient incorporation of N and In using a low growth temperature of 460 o C and V/III ratio of 20. The low growth temperature also prevents phase separation of these nitride materials as reported in existing literature [3]. In addition, SSMBE provides a much cleaner environment for hydrogen free growth ambient [4] to efficiently eliminate hydrogen related defects that are found in metal-organic chemical vapour deposition systems [4]. For the PL measurements, a 514.5 nm Ar-ion laser was used to excite the QW and the emitted PL signals were collected by a liquid N2 cooled Ge detector.
EXPERIMENTAL DETAILS AND DISCUSSIONS The double quantum well (DQW) structure grown by the SSMBE system has this structure: GaAscap/GaInAs-QW/GaAs-barrier/GaInNAs-QW/GaAs-buffer. The GaAs-barrier thickness is 80 nm, and this thickness is sufficient to eliminate the interaction between the two ~6 nm QWs’ wave-functions. The top GaInAs QW served as a reference QW to estimate the In compositions by PL. Both In and N compositions were then further estimated by fitting the measured XRD curve with the dynamic-theory simulated curve. The GaInNAs QWs’
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