P R O P E R T I ES OF L A T T I C E - M A T C H ED A ND S T R A I N ED i n d i um G a l l i um A r s e n i de E d i t ed by P A L L AB B H A T T A C H A R YA U n i v e r s i ty of M i c h i g a n, U SA IEE Published by: INSPEC, the Institution of Electrical Engineers, London, United Kingdom © 1993: INSPEC, the Institution of Electrical Engineers Apart from any fair dealing for the purposes of research or private study, or criticism or review, as permitted under the Copyright, Designs and Patents Act, 1988, this publication may be reproduced, stored or transmitted, in any forms or by any means, only with the prior permission in writing of the publishers, or in the case of reprographic reproduction in accordance with the terms of licences issued by the Copyright Licensing Agency. Inquiries concerning reproduction outside those terms should be sent to the publishers at the undermentioned address: Institution of Electrical Engineers Michael Faraday House, Six Hills Way, Stevenage, Herts. SG1 2AY, United Kingdom While the editor and the publishers believe that the information and guidance given in this work is correct, all parties must rely upon their own skill and judgment when making use of it. Neither the editor nor the publishers assume any liability to anyone for any loss or damage caused by any error or omission in the work, whether such error or omission is the result of negligence or any other cause. Any and all such liability is disclaimed. The moral right of the authors to be identified as authors of this work has been asserted by them in accordance with the Copyright, Designs and Patents Act 1988. British Library Cataloguing in Publication Data A CIP catalogue record for this book is available from the British Library ISBN 0 85296 865 5 Printed in England by Short Run Press Ltd., Exeter Foreword During the past two decades, considerable research has been devoted to the epitaxial growth techniques, material properties, and the device behaviour of the ternary solid solution Ga In As. This system is one of the best examples of a semiconductor material where the x 1x research and scientific interest are driven by significant technology needs and opportunities. In the early 1970s, Ga In As was investigated for optoelectronic devices. One application x 1 x was for light-emitting diode sources at the 1.06 |am emission wavelength of the Nd:YAG laser. This structure used vapour-phase epitaxy and composition grading from the GaAs substrate to the desired composition. Also at this time, the minimum in the optical fibre attenuation was near 1.05 \im which made it desirable to develop semiconductor sources and detectors for this wavelength. The other application was for photoemissive cathodes for the detection of Nd:YAG emission. These studies led to the determination of the room-temperature energy gap and lattice constant for the quaternary Ga In^ As P ^. x x 1 By the mid 1970s, liquid-phase epitaxial growth of Ga In As P on InP had been x 1 x 1 demonstrated and improvements in optical fibres had resulted in the transmission attenuation minimum at a wavelength of 1.3 |Lim. The activity due to the success of the InPZGa In As P ZInP double heterostructure laser made InP substrates readily available x 1x ly from commercial suppliers. Near the end of the 1970s, Ga In As/InP photodiodes with a 0 47 0 53 spectral dependence between wavelengths of 1.0 and 1.7 |um were demonstrated. During the two year period of 1977 to 1978, several innovations occurred which would ensure the technological importance of Ga In As. The first was the prediction from transport x 1x calculations that the saturated drift velocities of Ga In As, which lattice matched to InP, 0 47 0 53 would be higher than for GaAs, and, therefore, would be a promising material for microwave semiconductor devices. The next important result was the demonstration that high quality InP/Ga In As/InP double-heterostructure lasers could be fabricated. The third innovation 0 47 0 53 was the demonstration of modulation-doped heterostructures to provide enhanced carrier velocities for field-effect transistors. The hetero structure Al Ga AsZGaAs was used for this 1 demonstration because this system was the most mature technology. Modulation-doped heterostructures proved to be ideally suited to take advantage of the high electron saturated drift velocity of Ga In As. x 1x Another innovation in the early 1980s which provided many possible applications for Ga In As was the development of strained-layer superlattices which became known as x 1 x pseudomorphic layers. The lattice-matched heterostructure of Ga In AsZAl In As 047 053 048 052 also became useful in a variety of applications. By the mid 1980s, low threshold quantum well lasers had been demonstrated. A few years later, the erbium-doped fibre amplifier was shown to be well suited as postamplifiers, preamplifiers and in-line repeaters for optical fibre communication systems. This optical amplifier required a laser pump at a wavelength of 0.98 \xm. The best laser source was shown to be heterostructure lasers with Ga In As x 1x strained layer quantum well active layers. Also, the epitaxial growth technologies for molecular beam epitaxy and organometallic chemical vapour deposition matured to become suitable growth technologies for preparation of the required multiple thin layers for a variety of Ga In As heterostructures. From this point on, the publications on the growth, properties x 1 x and devices made with Ga In As grew almost exponentially with time. These devices x 1 x included photodiodes, metal-semiconductor-metal photodetectors, heterostructure lasers, surface-emitting vertical-cavity lasers, resonant tunnelling structures, quantum wires and dots, modulation doped field-effect transistors (or HEMTs), and heterojunction-bipolar transistors as well as optoelectronic integrated circuits. Threshold current for Ga In _ As heterostructure x 1 x lasers reached the mA range and current gain cutoff frequencies, f , of transistors exceeded T 100 GHz. With this rapid growth in the research and technology related to Ga In _ As, it is very timely x 1 x to collect the widely dispersed data describing this important semiconductor. This book, with material contributed by those whose work has made the field successful, will provide the information for further advances. I look forward to having this resource among my reference books. H. Craig Casey Jr. Department of Electrical Engineering Duke University Durham, NC 27708-0291 USA July 1993 Introduction The In Ga^ As (or GaInAs) ternary alloys span the range of lattice constants between the x x binary compounds GaAs (x = 0, bandgap 1.43 eV) and InAs (x = 1, bandgap 0.35 eV). These alloys and their heterostructures with wider bandgap semiconductors are playing a pivotal role in the study of quantum systems and in the development of high-performance electronic and optoelectronic devices. Except the alloy with composition In Ga As, which is 053 047 lattice-matched to InP, all other compositions are usually grown epitaxially on GaAs or InP substrates, and are therefore 'mismatched' materials. It is important to realise that almost all work - epitaxial growth, characterisation and device applications - with InGaAs is being done with thin (-1 \im) single layers or heterostructures formed with other compositionally different lattice-matched or mismatched semiconductors. Because of this, and due to the lack of 'bulk' InGaAs, this ternary compound has not been investigated and used in the same way as GaAs, InP, or Si. As a consequence, its thermal and mechanical properties are not known as well as those of GaAs or InP. Nonetheless, this has not hindered research and development of this compound and some of its more exciting composition- and strain-dependent material properties are being fully exploited to enhance device properties or to realise novel concepts. In Ga . As is a direct bandgap semiconductor throughout the entire composition range. x 1x In Ga As lattice-matched to InP, with a bandgap of 0.74 eV at room temperature, is an 0 53 0 47 important material for device applications. Very high electron mobility, high electron velocity, and a large intervalley separation in the conduction band are some of its favourable properties. Heterostructure devices using this compound, such as modulation doped field effect transistors, have demonstrated record DC, high-frequency, and noise performance at room and cryogenic temperatures. Lattice-matched heterostructures include In Ga As/InP, 0 53 0 47 In0.53Ga0.47As/In0.52A10.48AS' H.53G%47As/K-xGaxAs Pl-y and In0.53Ga0.47As/ y In Ga AL ,As. Its bandgap also corresponds to the spectral range where optical fibres have x 1 very low loss and dispersion. Therefore In Ga As is used for the development of sources, 0 53 0 47 modulators and detectors for optical communication. It is not often that one finds a material suitable for both electronic and optoelectronic applications. Due to this fortuitous coincidence, InGaAs and its heterostructures are being used for the development of optoelectronic integrated circuits (OEIC). The development and applications of mismatched In Ga As alloys are fascinating. Strained x 1 x semiconductors were initially developed as a tool for bandgap engineering. It was subsequently realised that biaxial strain in the material, incorporated during epitaxy, can be exploited for band structure engineering. Thus, there are two types of mismatched materials: relaxed, or strained-relieved, which can only be used for bandgap tailoring, and pseudomorphic, which can be used for bandgap and band structure engineering. The change in the band structure with biaxial strain uniquely alters the electronic and optical properties of semiconductors. These changes have been exploited to enhance the performance of devices such as FETs and quantum well lasers to unprecedented levels. It is also important to note that while In Ga ^As grown on GaAs is only compressively strained, Iiio.53±xGao.47+xAs x 1 grown on InP substrates can be both compressively or tensilely strained. It is amply evident that InGaAs and related heterostructures have established themselves as important materials for enabling technologies in microelectronics and optoelectronics. It is befitting, therefore, to dedicate a volume of the EMIS series to these materials and heterostructures. This volume describes their most important properties in the form of Datareviews written by renowned experts in the field. Their research contributions, and those of many others, have helped in the firm establishment of these heterostructures as technologically important materials. The volume is conveniently classified into 9 groups: (1) Structural Properties of InGaAs; (2) Thermal, Mechanical and Lattice Vibrational Properties of InGaAs; (3) Band Structure of Lattice-Matched and Strained InGaAs Alloys; (4) Transport Properties; (5) Surface Properties; (6) Radiative and Non-Radiative Recombination; (7) Optical and Electro-Optic Properties of InGaAs; (8) InGaAs Technology; and (9) Device Application of InGaAs and Related Heterostructures. It was felt that the volume would be incomplete without a chapter on device applications of InGaAs. Amongst the host of devices made with these materials, only the most important ones are described. Since heterostructures of InGaAs are often made with other lattice-matched quaternaries, it was deemed useful to devote an article specifically to these lattice-matched compounds. While many aspects of the information contained in this book are available in publications and review articles, this volume should evolve as a condensed and valuable resource for students, researchers and practising engineers. Before concluding, it is appropriate to comment on the chemical formula InGaAs itself. In accordance with the position of the constituent group III atoms in the periodic table, a more accurate description and formula is GaInAs. However, InGaAs is more often used at the present time and this nomenclature has been retained. Finally, I would like to thank John L. Seal's, Managing Editor of the EMIS series, for his support and patience and the authors and reviewers for their contributions. Pallab Bhattacharya Department of Electrical Engineering and Computer Science University of Michigan Ann Arbor, Michigan 48109-2122 USA July 1993 Contributing Authors DrS. Adachi Gunma University, Department of Electronic 2.1,2.4, Engineering, 1-5-1 Tenjin-cho, Kiryu 376, 3.4 Gunma, Japan Dr A.R. Adams University of Surrey, Department of Physics, 3.2 Guildford, Surrey, GU2 5XH, UK Professor I. Adesida University of Illinois, Microelectronics 8.3 Laboratory, 208 North Wright Street, Urbana, IL 61801, USA Dr S.A. Alterovitz NASA-Lewis, 21000 Brookpark Road, 7.1 M/S 54-5, Cleveland, OH 44135, USA Professor P.K. Bhattacharya University of Michigan, Department of 4.3, 6.3, Electrical Engineering and Computer Science, 8.2 1301 Beal Avenue, Ann Arbor, MI48109-2122, USA Dr D. Bimberg Technische Universitat Berlin, Institut 6.1,6.2 fur Festkorperphysik, Hardenbergstr. 36, 100 Berlin 12, Germany Dr N. Chand AT&T Bell Laboratories, Room 7C-304, 4.4, 8.1 600 Mountain Avenue, Murray Hill, NJ 07974, USA Dr Y.C. Chen University of Michigan, Department of 8.2 Electrical Engineering and Computer Science, 1301 Beal Avenue, Ann Arbor, MI48109-2122, USA Dr DJ. Dunstan University of Surrey, Department of Physics, 2.3 Guildford, Surrey, GU2 5XH, UK Dr M. Dutta U.S. Army Research Laboratory, Electronics 7.3,7.4 and Power Sources Directorate, AMSRL-EP-EF, Fort Monmouth, NJ 07703-5601, USA Dr N.K. Dutta AT&T Bell Laboratories, Optical Materials 9.2 Research, Room 6E-414, 600 Mountain Avenue, Murray Hill, NJ 07974-0636, USA Professor L.F. Eastman Cornell University, School of Electrical 4.1 Engineering, 424 Phillips Hall, Ithaca, NY 14853, USA Dr P.N. Fawcett Imperial College of Science, Technology and 5.1 Medicine, Interdisciplinary Research Centre, Prince Consort Road, London, SW7 2BZ, UK Dr E.A. Fitzgerald AT&T Bell Laboratories, Room 1E-447, 1.2 600 Mountain Avenue, Murray Hill, NJ 07974, USA Professor M. Ilegems Ecole Polytechnique Federate de Lausanne, 1.3 Microelectronics and Optoelectronics Institute, CH-1015 Lausanne, Switzerland Dr R.F. Karlicek Jr. AT&T Bell Laboratories, Room 7C-304, 8.1 600 Mountain Avenue, Murray Hill, NJ 07974, USA Dr K.W. Kim North Carolina State University, College of 4.2 Engineering, 213 Page Hall, Raleigh, NC 27695-7901, USA Dr P. Kordos Institut fur Schicht- und Ionentechnik, 5.3 Forschungszentrum Julich, W-5170 Julich, Germany Professor M.A. Littlejohn North Carolina State University, College of 4.2 Engineering, 213 Page Hall, Raleigh, NC 27695-7901, USA Professor S. Mahajan Carnegie-Mellon University, Department of 1.4 Metallurgical Engineering and Materials Science, Pittsburgh, PA 15213, USA Dr M. Marso Institut fur Schicht- und Ionentechnik, 5.3 Forschungszentrum Julich, W-5170 Julich, Germany Dr M. Matsuura Keio University, Department of Electrical 2.2 Engineering, Faculty of Science and Technology, 3-14-1 Hiyoshi, Yokohama 223, Japan Professor R. Merlin University of Michigan, College of Literature, 7.2 Science and the Arts, 3035C Randall Laboratory, Ann Arbor, MI48109-1120, USA Dr J. Pamulapati U.S. Army-ETDL, SLCET-ED, Fort Monmouth, 7.3,7.4 NJ 07703-5000, USA Professor D. Pavlidis University of Michigan, Department of 9.3 Electrical Engineering and Computer Science, 1301 Beal Avenue, Ann Arbor, MI48109-2122, USA Professor T.P. Pearsall University of Washington, Department of 9.1 Electrical Engineering, 101 Wilson Hall, M/S FB-IO, Seattle, WA 98195, USA Dr A.D. Prins University of Surrey, Department of Physics, 2.3 Guildford, Surrey, GU2 5XH, UK Dr J. Shah AT&T Bell Laboratories, Room 4D-415, 6.4 Holmdel, NJ 07733, USA Professor J. Singh University of Michigan, Department of Electrical 3.1,3.5 Engineering and Computer Science, 1301 Beal Avenue, Ann Arbor, MI 48109-2122, USA Dr B. Srocka Technische Universitat Berlin, Institut fur 6.1,6.2 Festkorperphysik, Hardenbergstr. 36, 100 Berlin 12, Germany Professor G.E. Stillman University of Illinois at Urbana-Champaign, 3.3 Center for Compound Semiconductor Microelectronics, 151 Microelectronics Laboratory, 208 North Wright Street, Urbana, IL 61801, USA Professor G.B. Stringfellow University of Utah, Department of Materials 1.1 Science, 304 EMRO, Salt Lake City, UT 84112, USA Professor N.S. Takahashi Keio University, Department of Electrical 2.2 Engineering, Faculty of Science and Technology, 3-14-1 Hiyoshi, Yokohama 223, Japan Dr H. Tian North Carolina State University, College of 4.2 Engineering, 213 Page Hall, Raleigh, NC 27695-7901, USA Professor CR. Wie State University of New York at Buffalo, 8.4 Department of Electrical and Computer Engineering, Bonner Hall, Amherst, NY 14260, USA Professor H.H. Wieder University of California at San Diego, 5.2 Department of Electrical and Computer Engineering, Mail Code 0407, La Jolla, CA 92093-0407, USA Dr V.A. Wilkinson University of Surrey, Department of Physics, 3.2 Guildford, Surrey, GU2 5XH, UK Professor CW. Wilmsen Colorado State University, Department of 5.4 Electrical Engineering, Fort Collins, CO 80523, USA Dr J.E. Zucker AT&T Bell Laboratories, Room 4F-319, 7.5 Crawfords Corner Road, Holmdel, NJ 07733, USA