Improved Carrier Transport in Intermixed GaAs/AlGaAs Laser Structure With Multi-Quantum Wells Cladding
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ABSTRACT A GaAs/A1GaAs laser structure with multi-quantum-well cladding layer has been employed to investigate the group mI interdiffusion. With this structure the photoluminescence (PL) signals from both the top C doped cladding layers and the laser active region quantum wells can be observed simultaneously. In contrast to the depth dependence of the group III vacancy enhanced interdiffusion, the quantum wells in the thick top cladding layer showed a uniform layer intermixing and the extent of intermixing was less than that observed in the quantum wells of the laser active region. The Al-Ga interdiffusion coefficient, DAI-Ga, of the cladding layer is about 4 times less than that of the active region. A more efficient carrier transport from the cladding layer to the active region in the intermixed sample was deduced from the temperature varied PL spectra. The built-in electric field is proposed to enhance the vacancy diffusion in the active region. INTRODUCTION Quantum well intermixing (QWI) has attracted considerable interest in the past decades due to its wide applicability in photonic integrated circuit and the study of material characteristic.", 2 Impurity induced disordering (IlD) and impurity free vacancy enhanced disordering (JFVD) are two commonly used methods for post growth adjustment of the energy levels in quantum wells. The later one has minimum effect on the crystal quality and optical propagation loss. It is clear now that in IFVD, the group III interdiffusion is governed by the negatively charged Ga vacancy mechanism on the group 111sublattice. 3,4 The degree of group El interdiffusion depends on the concentration and diffusivity of the Ga vacancy. The concentration of Ga vacancy can be altered by the surface condition. Integrated photonic devices are usually fabricated on a common p-i-n laser structure consisting of a thin active quantum well region and thick doped cladding regions. Former studies are mainly based on the quantum well structures with either no dopant or with the dopant distributed throughout the region of interest. It is important to compare the vacancy diffusion through the thick doped cladding layer with that of the undoped active region and at the same time study the effect of the electric field that exists in a laser structure on the Ga vacancy diffusion. On the other hand, the superlattice structure used in the cladding layer of a GaAs/AlGaAs laser structure can improve both the electron and hole transport through the thick cladding layer and thus raises the overall efficiency of the laser. 5 In this paper we employ the GaAs/Alo.2 Gao.8 As quantum well laser structure with heavily C and Si doped multiquantum-well cladding layer to study the quantum well intermixing process. With this structure both the cladding layer and the active region signals E-mail: [email protected] 213 Mat. Res. Soc. Symp. Proc. Vol. 618 © 2000 Materials Research Society
can be observed at the same time. Also we can study the electric field effect on the interdiffusion process during high temperature a
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