Morphological, optical and structural properties of zero-net-strained InGaAsP/InP structures grown by LP-MOVPE for 1.55mum laser applications

Abstract

Zero-Net-Strained ZNS InGaAsP InGaAsP InP Multi Quantum Wells MQW structures grown by L o w Pressure Metalorganic Vapor Phase Epitaxy for 1.55 m laser applications were investigated using atomic force microscopy, photoluminescence spectroscopy and X-ray di raction. The morphology exhibits a strong anisotropic and modulated behavior. The photoluminescence spectrum shows a broad emission band below the fundamental quantum well transition. The results indicate a strong in uence of the growth rate, growth temperature and barrier composition on the surface morphology, and on the optical and structural properties of the ZNS structures. Ridge wave-guide ZNS-MQW laser structures grown at optimized conditions exhibited excellent electro-optic characteristics with low threshold current and high e ciency. I IntroductionInGaAsP quaternary alloy materials epitaxially grown on InP substrates have been extensively used to fabricate optoelectronic devices such as lasers, photodetectors, optical ampli ers and modulators for telecommunication applications. The introduction of a biaxial strain is able to modify the material electronic structure and this can be exploited to enhance the performance of optoelectronic devices. However, a strain relaxation process may occur if the layer thickness exceeds a critical value and mis t dislocations are created 1 . It is possible to compensate the total strain of a m ulti-quantum well MQW structure through the use of tensile strained barriers and compressive strained wells. Such structures are referred as zero-net-strained ZNS . Nevertheless, the strain relaxation can occur prior to the mis t generation through elastic mechanisms. Also, the quaternary InGaAsP alloy m a y b e a ected by the miscibility gap 2,3 , where a range of compositions and temperatures exist and the solid solution is energetically unstable. These mechanisms produce undulation at the interfaces, composition uctuations, wavy morphologies and contribute to degrade the optical and structural properties of the grown layers 4-6 . High quality lattice matched GaInAs InP and GaInAs AlInAs superlattices with up to 100 periods, grown by M O VPE were obtained using low growth temperature and high growth rate 7 .In this work we present a systematic study of ZNS InGaAsP InGaAsP InP MQW heterostructures grown by L o w Pressure Metalorganic Vapor Phase Epitaxy LP-MOVPE for 1.55 m laser applications. The effect of growth rate, growth temperature and barrier composition on the surface morphology and on the optical properties of ZNS structures were investigated using atomic force microscopy, photoluminescence spectroscopy and double crystal X-ray di raction. II ExperimentThe materials analyzed in this work were grown on InP:S 001 substrates by LP-MOVPE at the growth temperature T g of 640 and 670 o C under a reactor pressure of 70Torr. Arsine AsH 3 and Phosphine PH 3 h ydrides were used as As and P source, respectively, and trimethylindium TMIn and triethylgalium TEGa organometallic compounds as In and Ga sources. Growth rates R of 2.5 A...