The Effect of an Electric Field on the Optical Absorption in GaSe

Abstract

GaSe exhibits a relatively high exciton absorption well pronounced even at room temperature (1). Measurements of the electroabsorption in the exciton region of the absorption spectrum of GaSe at liquid helium temperature have been described in the literature (2). From the results of that work it follows that the electroabsorption effect observed by the authors i s associated with an exciton line broadening.We studied the change in transmission in the exciton absorption region of GaSe at room temperature. Measurements were carried out both with static and pulsed electric field. To diminish the influence of heating, doped high-resistivity ( e > 10 Q /cm) specimens of GaSe were used. A s is seen from these curves the character of transmission varies with the specimens.In the transmission spectrum of GaSe specimens of the first type (Fig. l a ) the absorption maximum at A = 618 nm is well pronounced, whereas in the transmission spectrum for specimens of the second type (Fig. lb) there is no such maximum.Structure investigations have shown that the GaSe specimens of the second type exhibit hexagonal modification whereas in specimens of the first type hexagonal and rhombohedra1 modifications were present. The possibility of the Occurrence of these modifications in GaSe crystals was mentioned in (3).It has been found that for specimens of the first and second type the transmission in electric field changes in a different manner. For specimens of the first type the positive and negative peaks are observed distinctly in the spectral dependence of the 5 physica