Optical properties of Ga2Se3 under high pressure

The optical absorption spectrum of beta -Ga2Se3 has been measured at pressu res up to 7 GPa using a diamond anvil cell. The exciton absorption is obser ved in the optical absorption spectrum at ambient pressure. With increasing pressure, the exciton line shifts to the higher energy region. From the sh ift of the exciton line with pressure, the pressure dependence of the band Sap energy (dE(g)/dP) is estimated to be (45 +/- 4) meV/GPa at ambient pres sure. This pressure coefficient agrees well with that obtained previously b y photoluminescence measurements. The Pressure coefficient of the hand gap and the intensity of the exciton line decrease gradually with pressure, and become almost zero at 7 Gpa, what suggests that a pressure induced direct- to indirect-gap semiconductor transition occurs.