Effect of incident laser fluence on the structure of pulsed-laser deposited AlN films

Polycrystalline AIN films were synthesized on (100)Si substrates by pulsed laser deposition at 800°C and different incident laser fluences and nitrogen ambient pressures. We used two KrF* (λ= 248 nm) excimer laser sources generating pulses of 7.4 and 25 ns duration, respectively. The incident laser intensity was kept constant in all experiments within the range (3 -4) x 10 8 W/cm 2 . The effect of incident laser fluence on the structure and defects of pulsed laser deposited AIN films was investigated by X-Ray diffractometry and frequency-dependent admittance measurements at zero DC bias voltage. The X-ray diffraction results revealed a polycrystalline structure with predominantly cubic crystallites in films deposited with short laser pulses (laser fluences of 2.5 and 3.7 J/cm 2 , respectively). With longer laser pulses and large fluence (8.6 J/cm 2 ), the prevalent crystalline phase changed from cubic to hexagonal. For intermediate deposition conditions (long pulses and lower fluences), the co-existence of the two crystalline phases was recorded. In addition, the admittance measurements in the frequency range of 1 kHz-20 MHz evidenced the contribution of deep levels to the frequency dispersion of the capacitance and current conductance of AlN MIS structures.