FIR LASER SPECTROSCOPY OF IMPURITIES IN SEMICONDUCTORS

A concise review of the FIR magnetooptical investigations of the photo excitation of shallow impurities in semiconductors with the use of the molecular lasers optically pumped with carbon dioxide lasers is prese nted. The goal of the article is to demonstrate the abilities of the a bove technique by selecting some typical examples. The primary conside ration is given to the photoconductive detection of the photoexcitatio n, mainly to the photo-thermal ionization technique. It is shown that the high resolution of laser spectroscopy is capable not only of chara cterizing the shallow impurities themselves, but of giving valuable in formation on other defects and impurities that the shallow impurities interact with. The illustration of the central cell structure of donor photo-excitation spectra for the purest samples of GaAs is used to de monstrate the ability of the technique. Some examples of mechanisms of line broading are also discussed. Illustrations of effects of Coulomb correlations of charged impurities in compensated semiconductors on l inewidth are provided. A brief description of examples of application of FIR laser spectroscopy to a study of acceptors in II-VI semiconduct ors, including semimagnetic semiconductors is also included.