This volume examines a timely problem in solid state physics, the condensation of ex citons in semiconductors. The papers in this volume describe a new approach to the study of exciton condensation based on microwave-frequency conductivity and the breakdown of an ex citon gas in a microwave field, an effect discovered by the authors. These methods have been used in extensive studies of germanium and have produced important new data about the con densation process. In addition to the experimental data, a theory is presented for the micro wave breakdown of excitons in the presence of electron-hole droplets. Also included are three articles devoted to the experimental aspects of low-temperature semiconductor research. This volume will interest scientists and engineers involved· with research in solid state physics. CONTENTS Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 A. A. Manenkov Microwave Studies of Exciton Condensation in Ge. • • • • • • • • • • • • • • • • • • • • • • • • • 3 G. N. Mikhailova Microwave Breakdown of Excitons and the Kinetics of Free Carriers and Excitons in Germanium in the Presence of Electron-Hole Drops. • • • • • • • • • • • • 37 A. A. Manenkov, V. A. Milyaev, G. N. Mikhailova, V. A. Sanina, and A. S.

Inhalt
Microwave Studies of Exciton Condensation in Ge.- Microwave Breakdown of Excitons and the Kinetics of Free Carriers and Excitons in Germanium in the Presence of Electron-Hole Drops.- Microwave Breakdown Studies of Exciton Condensation in Ge and Luminescence during One- and Two-Photon Excitation of Carriers.- Microwave Absorption by Nonequilibrium Current Carriers in Germanium. A Method for Determining Carrier Concentration.- Microwave Methods for Studying Exciton Condensation in Semiconductors.- A Helium-3 Refrigerator for Studying Excitons in Ge at Temperatures Below 1°K.- Effects of Laser Heating on Germanium Samples at Liquid Helium Temperature.- Cyclotron Resonance and Radiative Recombination in Pure Ge with Laser Excitation.