Dislocations in GaAs p-i-n diodes grown by hydride vapour phase epitaxy A. Sa ¨yna ¨tjoki Æ A. Lankinen Æ T. O. Tuomi Æ P. J. McNally Æ A. Danilewsky Æ Y. Zhilyaev Æ L. Fedorov Ó Springer Science+Business Media, LLC 2007 Abstract Hydride vapour phase epitaxy grown all- epitaxial p-i-n structures were studied by synchrotron X-ray topography. Three types of process induced dislo- cations were found: short threading dislocations, long straight interfacial dislocations and circular arc disloca- tions. The majority of the dislocations observed are short straight threading dislocations, the density of which is typically about 5000 cm –2 . The dislocations at the p-i interface are long straight lines parallel to [110]. They are screw dislocations having their Burgers vector parallel to [110], calculated from the contrast analysis of the well resolved dislocation images. One sample also showed a dense misfit dislocation network at the n-side. However, no misfit dislocations were seen in the back-reflection topographs of the n-side of the other samples, which shows that it is possible to grow a misfit-dislocation free n-type GaAs layer onto the substrate side of a hydride vapour phase epitaxy grown GaAs surface after proper substrate removal. 1 Introduction Hydride vapour phase epitaxy (HVPE) is a rapid growth technique, which is suitable for depositing thick ultra-pure as well as doped epitaxial layers on top of a substrate wafer [1]. Thick HVPE grown GaAs layers have been used in various types of devices, such as lasers [2] and nonlinear optics devices [3]. Thick layers also enable free-standing epitaxial structures, which are used e.g. as GaN substrates [4, 5]. Ultra-pure all-epitaxial materials are also desired in detector manufacturing. Such GaAs p-i-n diode structures, grown by open tube chloride HVPE, are studied in this work by synchrotron X-ray topography. The main interest in this work is the defect structure of the samples. In detectors one of the important properties is the leakage current, upon which defects like dislocations are thought to have an influence. The dislocations may attract harmful residual impurities, and in this way act as gettering centres. Contrary to such a beneficial effect the dislocations may actually behave as channels for electric current through the diode and worsen its device performance. In either case it is important to know the defect structure of the HVPE grown p-i-n diode. X-ray diffraction topography using synchrotron radiation is an ideal detection method for measuring the dislocation density as well as determining the type and spatial distribution of the dislocations [6]. The technique is also rapid compared to those using conventional X-ray sources. It can be applied in different measuring geometries both in the transmission and in the back-reflection modes without any careful alignment of the sample. 2 Experimental The HVPE process utilizes Ga metal and AsCl 3 as the source materials with H 2 as the carrier gas. H 2 reacts with A. Sa ¨yna ¨tjoki (&)  A. Lankinen  T. O. Tuomi Micro and Nanosciences Laboratory, Helsinki University of Technology, Micronova, Espoo, Finland e-mail: antti.saynatjoki@tkk.fi P. J. McNally RINCE, Dublin City University, Dublin, Ireland A. Danilewsky Kristallographisches Institut, Universita ¨t Freiburg, Freiburg, Germany Y. Zhilyaev  L. Fedorov A. F. Ioffe Physico-Technical Institute, St. Petersburg, Russia 123 J Mater Sci: Mater Electron DOI 10.1007/s10854-007-9303-8