Studies of carrier dynamics in unintentionally doped gallium nitride bandtail states

Ultrafast carrier dynamics of bandtail states in an unintentionally doped g allium nitride sample was investigated using femtosecond transient transmis sion measurements. The transient responses of shallow bandtail states resem ble those of above band gap extended states. The transient responses of the deep bandtail states are, on the other hand dominated by carrier transfer into the lower energy states through phonon assisted tunneling suggesting t hat the deep bandtail states are localized states. (C) 2001 American Instit ute of Physics.