1063-7826/04/3803- $26.00 © 2004 MAIK “Nauka/Interperiodica” 0313 Semiconductors, Vol. 38, No. 3, 2004, pp. 313–318. Translated from Fizika i Tekhnika Poluprovodnikov, Vol. 38, No. 3, 2004, pp. 325–330. Original Russian Text Copyright © 2004 by Avrutin, Agafonov, Vyatkin, Zinenko, Izyumskaya, Irzhak, Roshchupkin, Steinman, Vdovin, Yugova. 1. INTRODUCTION The active interest in epitaxial growth of Si 1 – x Ge x layers on Si substrates is related primarily to the fact that new electronic and optoelectronic devices can be fabricated on the basis of SiGe/Si heterostructures. As is well known, SiGe films obtained as a result of pseudomorphic growth on Si substrates are found to be elastically stressed owing to the large mismatch between the lattice parameters of Si and Ge (4.12%). At the same time, SiGe layers with a high degree of relax- ation are required to fabricate certain types of devices based on SiGe/Si structures (field-effect transistors, photodetectors, and solar cells) [1]. In addition, the use of relaxed SiGe buffer layers presents additional oppor- tunities for controlling the energy-band structure and for integrating devices based on III–V compounds into conventional silicon technology. It is well known that the relaxation of elastic stresses in heterostructures occurs if the critical thickness of an epitaxial layer is exceeded by introducing misfit dislocations into the vicinity of the interphase boundary. It is important that tilted segments of the dislocations introduced thread through the epitaxial layer [2]. The presence of thread- ing dislocations in the film significantly impairs its characteristics and makes it virtually impossible to use such structures in electronic and optical devices [3]. Therefore, reducing the threading-dislocation density is the most important problem in the development of elec- tronic devices based on SiGe/Si heterostructures. At present, epitaxial growth of Si 1 – x Ge x buffer lay- ers with a gradient of Ge concentration is the most highly developed method for fabricating SiGe films with a high degree of relaxation and a comparatively low density of threading dislocations (10 5 –10 6 cm –2 ) [4, 5]. However, in order to obtain films with a low den- sity of threading dislocations, one has to ensure that gradients of Ge concentration are very low (typically, 5–10% per micrometer). This circumstance necessi- tates a large thickness of the buffer layer (several micrometers); as a result, growth times are long and a large amount of material is consumed. This signifi- cantly increases the production cost of devices and makes it more difficult to integrate them into Si inte- grated circuits. Another serious drawback of the method described above is the large-amplitude surface roughness of the buffer layers with a gradient of Ge concentration [6]. Introducing nonequilibrium point defects into the heterostructures is an alternative approach to solving the above-formulated problem. It has been recently shown that nonequilibrium point defects introduced into the heterostructures promote the relaxation of stresses and, at the same time, can reduce the density of threading dislocations to a great extent [7–15]. Point defects can be introduced by low- ering the growth temperature, which leads to a satura- tion of the growing layers with nonequilibrium point defects of the vacancy type [7–12], and also by irradiat- ing the layers with low-energy ions in the course [11–13] SEMICONDUCTOR STRUCTURES, INTERFACES, AND SURFACES Low-Temperature Relaxation of Elastic Stresses in SiGe/Si Heterostructures Irradiated with Ge + Ions V. S. Avrutin*, Yu. A. Agafonov*, A. F. Vyatkin*^, V. I. Zinenko*, N. F. Izyumskaya*, D. V. Irzhak*, D. V. Roshchupkin*, É. A. Steinman**, V. I. Vdovin***, and T. G. Yugova**** *Institute of Microelectronic Technology, Russian Academy of Sciences, Chernogolovka, Moscow oblast, 142432 Russia ^e-mail: vyatkin@ipmt-hpm.ac.ru **Institute of Solid-State Physics, Russian Academy of Sciences, Chernogolovka, Moscow oblast, 142432 Russia ***Institute for Chemical Problems in Microelectronics, Moscow, 117571 Russia ****State Research Institute for the Rare-Metals Industry, Moscow, 119017 Russia Submitted June 18, 2003; accepted for publication July 1, 2003 Abstract—Pseudomorphic Si 0.76 Ge 0.24 /Si heterostructures grown by molecular-beam epitaxy were irradiated with 350-keV Ge + ions at a temperature of 400°C so that the peak of the ions’ energy losses was located within the silicon substrate (deeper than the SiGe–Si interface). The effect of ion implantation on the relaxation of elas- tic stresses and the defect structure formed as a result of postimplantation annealing is studied. It is found that annealing at a temperature even as low as 600°C makes it possible to ensure a very high degree of relaxation of elastic stresses in the heterostructure and a comparatively low density of threading dislocations in the SiGe layer (<10 5 cm –2 ). The results obtained make it possible to suggest a method for the formation of thin SiGe/Si layers that feature a high degree of relaxation, low density of threading dislocations, and a good surface morphology. © 2004 MAIK “Nauka/Interperiodica”.