Pulsed sub-band-gap photoexcitation of AlN

Since AlN is a wide band-gap semiconductor it is usually not possible to in duce photocurrents with light below 6.2 eV of energy. However, employing hi gh power density laser pulses of 266 nm (4.66 eV) and 532 nm (2.33 eV), we succeeded to monitor the transient photocurrent (TPC) in transverse and par allel configuration using metal-insulator-metal (MIM) structures and single films, respectively. Absorption is possible due to excitation from deep de fects, which are indicated by the power-law decays of the photocurrents wit h exponents below unity. The thickness dependence of the magnitude of the p hotocurrent and RES profiling lead us to believe that photocurrents origina te mainly from an oxygen-rich transition layer. Films down to a thickness o f 5 Angstrom can still be characterized by TPC measurements. (C) 2001 Elsev ier Science B.V. All rights reserved.