472 Journal of Luminescence 31 & 32(1984) 472-475 North-Holland. Amstei datrr EMISSION OF FREE AND BOIJND EXCITONS IN GaSe AND InSe CRYSTALS IN DIRECT AND INDIRECT TRANSITION REGION Yu.P. GNATENKO, P.A. SKTJBENKO, Yu.I.ZHIRKO, O.V.FIALKOVSKAYA Physics Institute, Academy of Sciences of the Ukrainian SSR. 252650, Kiev, Prospect Nauki 144 (USSR) 1. INTRODUCTION The GaSe and InSe crystals belonging to A 3BC semiconductor compounds are characterized by the presence of a great number of intensive emission lines located near the emission line of a free exciton. The presence of various crystalline modifications notab- ly complicates their interpretation. The form of emission spect- rum is strongly dependent upon defect concentration in the crys- tal, which can be decreased by doping the GaSe crystals with Fe group impurities of definite concentrations (~ O.1%)~. This paper deals with perfect spesimens of ~ —modification, in which the number of defects is significantly reduced by doping the GaSe crystals with Co atoms and the InSe crystals with Cr atoms of 0.001% concentration and also by annealing them in inert Ag atmosphere. 2. EXPERIMENTAL RESULTS AND DISCUSSION Pig. 1 shows the luminescence spectrum of GaSe:Co crystal with impurity concentration of 0.001%. The results show that the group of narrow lines is polarized mainly EIC, the wide bands being B I) C. The analysis of the temperature dependence of narrow line intensity and energy location showed2 that they correspond to a set of series consisting of bound triplet exciton lines and their satellites involving 14.5 meV phonons. The wide emission bands of 2.039 eV and 2.008 eV energy are stipulated by radiative decay of indirect excitons with emission of one or two TO—phonons of 29 meV energy. It is to be noted, that the location of these bands depends upon the excited face orientation with respect to the 0—axis. This dependence stems from TO—phonon energy change when their direction of propagation varies. The nona.polarized emission band at 2.031 eV results from structural defects the 0022—2313/84/$03.OO© Elsevier Science Publishers By. (North-Holland Physics Publishing Division)