I am happy indeed to write a foreword to this book. Since it was founded, the A. F. Ioffe Institute in Leningrad has been in the forefront of semiconductor research. I visited it in 1934, and vividly remember A ¿. F. Ioffe himself and J. Frenkel and their kindness to me, and to others attending the meeting to celebrate the hundredth anniversary of Mendeleev. In the last years my own work on non-crystalline semiconductors has been strongly influenced by the work of B. T. Kolomiets and his co-workers. The English-speaking world should know the great Institute better, and this book will, I am sure, help this to happen. Nevill Mott Cambridge, June 1985 v Contents INTRODUCTORY PART Abram Fyodorovich Ioffe (29th October 1880 - 14th October 1960) 3 V. M. Tuchkevich and V. Ya. Frenkel Semiconductors: A New Material for Electrical Engineering 11 A. F. Ioffe EXPERIMENTAL PART Photovoltaic Solar Energy Conversion 19 Zh. 1. Alferov New Optical Methods in Semiconductor Research 37 B. P. Zakharchenya Reemission, Quantum Efficiency and Lifetimes of Radiative Recombination in A3BS Semiconductors and Heterostructures 53 D. Z. Garbuzov Interacting Excitons in Germanium and Silicon 87 P. D. Altukhov, V. M. Asnin and A. A. Rogachev Liquid Semiconductors 129 A. R. Regel and A. A. Andreev Chalcogenide Vitreous Semiconductors 143 B. T. Kolomiets, E. A. Lebedev, V. M. Lyubin, T. F. Mazets and T. N. Mamontova vii viii CONTENTS Electron and Hole Recombination in Narrow Gap Semiconductors 169 B. L. Gelmont and V. I.