Room-Temperature CW Operation of SQW Lasers on Si Grown with AiGaAs/AlGaP Intermediate Layers by MoCVD
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ROOM-TEMPERATURE CW OPERATION OF SQW LASERS ON Si GROWN WITH AIGaAs/A1GaP INTERMEDIATE LAYERS BY MOCVD T. EGAWA, Y. HAYASHI, T. GEORGE, T. SOGA, T. JIMBO AND M. UMENO Department of Electrical and Computer Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466, Japan
ABSTRACT The heterointerfaces of single quantum wells (SQWs) and the characteristics of SQW lasers on Si substrates grown with Al 0 Gao 5 As/Al 0 5 5 Ga0 . P intermediate layers (AlGaAs/AlGaP ILs) entirely by 'CVD are reported. The surface morphology and the heterointerfaces of SQWs grown on Si substrates with the AlGaAs/AlGaP ILs are smoother than those of the two-step-grown sample. The two-dimensional growth of the AlGaAs/AlGaP ILs on a Si substrate contributes to obtain the smooth
heterointerface.
The excellent lasing characteristics are obtained by the
AlGaAs/AlGaP ILs, which are caused by the smooth heterointerfaces. The lasers grown with the2 AlGaAs/AlGaP ILs show the averaged threshold current density of 1.83 kA/cm and the averaged differential quantum efficiency of 51.9 %under cw condition at room temperature. INTRODUCTION Heteroepitaxial growth of GaAs on Si (GaAs/Si) offers important advantages for such applications as monolithic integration of optoelectronic and microelectronic devices, and optical interconnections between integrated circuits. In order to realize these applications, room-temperature continuous-wave (cw) operation of AlGaAs/GaAs laser on a Si substrate with a low threshold current is a key technology. By using molecular beam epitaxy (MBE) and/or metalorganic chemical vapor deposition (MOCVD), all of the room-temperature cw operating lasers have been directly grown (two-step growth technique) on Si [1-3]. The GaAs/Si still has such problems as the high density of misfit and threading dislocations, roughness of surface morphology and unintentional Si autodoping. These problems affect device performances, namely, shortening device lifetime, increasing threshold current density and decreasing differential quantum efficiency. We have reported that thermal cycle annealing and SiO back coating are useful to obtain a low-threshold cw operation of the single quantum well (SQW) laser on Si [3]. The roughness of the surface morphology of the GaAs/Si, especially those grown by the two-step growth technique, causes heterointerface roughness in the quantum well (QW) structure. It is known that variation of band gap with distance through the interface, fluctuation in the thickness and roughness of the heterointerface affect the optical and transport properties of heterostructure devices [4]. In this paper, we study the heterointerfaces of SQWs and SQW laser characteristics on Si grown with Ale •Ga ý; As/Al 0 5 5 Ga0 P45 intermediate layers (AlGaAs/AlGaP ILs) by the M86 D chnique, and compare them with those grown by the two-step growth technique.
EPITAXIAL GROWTH AND FABRICATION PROCESS 720-nm-thick sputtered Si0 2 back-coated n-type (Sb doped, 0.02 Q-cm) Si substrates were used for the epitaxial growth 13,4]. All
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