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

A. SZEKERES1, S. SIMEONOV1, S. BAKALOVA1, I. MINKOV1, A. CZIRAKI2, C. RISTOSCU3,* , G. SOCOL3, G. DORCIOMAN3, I. N. MIHAILESCU3

Affiliation

  1. Institute of Solid State Physics, Bulgarian Academy of Sciences, 72, Tzarigradsko Chaussee blvd., 1784 Sofia, Bulgaria
  2. Eotvos Lorand University, 1 Pazmany Peter setany, 1117 Budapest, Hungary
  3. National Institute for Lasers, Plasma, and Radiation Physics, PO Box MG-54, RO-77125, Magurele, Ilfov, Romania

Abstract

Polycrystalline AlN films were synthesized on (100)Si substrates by pulsed laser deposition at 800oC 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 108 W/cm2 . The effect of incident laser fluence on the structure and defects of pulsed laser deposited AlN films was investigated by X-Ray diffractometry and frequency-dependent admittance measurements at zero DC bias voltage. The Xray 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/cm2 , respectively). With longer laser pulses and large fluence (8.6 J/cm2 ), 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..

Keywords

Crystalline Aluminium nitride thin films, Structure and defects, AC conductivity mechanism, Pulsed laser deposition.

Submitted at: June 19, 2009
Accepted at: Feb. 27, 2010

Citation

A. SZEKERES, S. SIMEONOV, S. BAKALOVA, I. MINKOV, A. CZIRAKI, C. RISTOSCU, G. SOCOL, G. DORCIOMAN, I. N. MIHAILESCU, Effect of incident laser fluence on the structure of pulsed-laser deposited AlN films, Journal of Optoelectronics and Advanced Materials Vol. 12, Iss. 3, pp. 542-546 (2010)