Modulator Structure Using In(As,P)/InP Strained Multiple Quantum Wells Grown By Gas-Source MBE
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MODULATOR STRUCTURE USING In(As,P)/lnP STRAINED MULTIPLE QUANTUM WELLS GROWN BY GAS-SOURCE MBE H. Q. HOU, T. P. CHIN, B. W. LIANG, and C. W. TU Department of Electrical and Computer Engineering, University of California at San Diego, La Jolla, CA 92093-0407 ABSTRACT In(As,P)/InP strained multiple quantum wells (SMQW's) were grown with gas-source molecular-beam epitaxy (GSMBE). A successful control of the As composition was achieved over a wide range by using two techniques. High-quality samples were characterized structurally and optically by x-ray diffractometry, transmission electron microscopy (TEM), photoluminescence (PL) and absorption measurements. Excitonic emission energy and the critical layer thickness of In(As,P)/InP SMQW's are calculated as a function of the As composition. The results show that 1.06, 1.3 and 1.55 1 m excitonic emission can be achieved at room temperature using this material system. We also discuss the perspective of using In(As,P)/InP SMQW's for modulator application. INTRODUCTION Inl-yGayAsxPl-x grown on InP is promising for long-wavelength optoelectronic devices because its fundamental band gap is suitable for infrared emitters and detectors operated between 0.9 to 2.0 /m. 11 [ Extensive studies of the growth and characterization as well as device applications have been presented based on this material system.[24] In contrast, InAsxPlIx/InP, a special case of the quaternary InliyGayAsxPl-x/InP, has received little attention from various advanced crystal growth techniques, such as organometallic vapor phase epitaxy (OMVPE)[ 5,6] or molecular beam epitaxy (MBE).[7] The growth of InAsxPl-x reduces difficulties in the composition control of quaternary Inl-yGayAsxPl-x, and provides a new degree of freedom for device design by tailoring the band structure with built-in biaxial strain. More importantly, an independent control of the layer thickness and alloy composition can be achieved in GSMBE growth since the thickness is determined by the indium beam flux and the composition by the AsH 3 and PH 3 flow-rate fraction. This greatly simplifies the growth control to tune excitonic emission to a desired wavelength for optoelectronic devices. However, since arsenic incorporates with indium much more significantly than phosphorus,18S the difficulty in obtaining a desired arsenic composition in InAsxPl-x arises from the need for accurate control of the hydride flow-rate fraction, especially in the low x region. Moreover, the critical layer thickness[9, 10] limits pseudomorphic growth of the InAsxPl-x layer when the composition x is large. In this paper we report a successful growth of device-quality InAsxPt. x/InP SMQW's by GSMBE. High-quality InAsxP]_x layers are obtained in SMQW structures for optical modulators operated at 1.06, 1.3 and 1.55 /•m. Samples with various arsenic composition and layer thickness are characterized structurally and optically. The viability of modulator application by using InAsxPl-x/InP SMQW's will be discussed based on the emission wavelength and critical layer thick
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