Screening of optical-phonon—hole interaction by photogenerated carriers in the layered semiconductor gallium selenide

The time-resolved photoluminescence kinetics of GaSe has been measured at room temperature. The rise time of the spontaneous-emission band is within the response time of the picosecond laser pulse duration and streak camera ({≤}20 ps) when the photogenerated carrier density is below 5 ×{} 10¹⁸ cm^-3 and increases to a measurable value when the carrier density is above 5 ×{} 10¹⁸ cm^-3. The increase in the rise time of the spontaneous-emission band arises from the screening of nonpolar optical-phonon emission from hot photogenerated carriers due to high photogenerated carrier density. On the other hand, the rise time of the stimulated-emission band is not time resolved with increasing picosecond laser pulse intensity.