AIN thick films for power electronic device applications

In recent years, a lot of efforts have been made in growth of AlN films because of its promising potential for applications in electronic devices, such as surface acoustic wave devices due to its very high speed acoustic wave. Fairly high thermal conductivity and small difference in thermal expansion coefficients make AlN important in GaAs integrated circuit (IC) technology. The effort toward combining the superior electrical properties of GaAs and excellent thermal properties of AlN to achieve high power microwave applications is presented. Different experimental conditions such as different flow rates of nitrogen and argon, different sputtering powers and different substrate temperatures have been employed. AlN thick films as thick as 30 μm have been obtained. X-ray diffraction. Scanning electron microscopy, Atomic force microscopy, Raman and FTIR spectroscopy have been applied to investigate the quality of the films. From the results, it was found that the smooth and pure AlN films were always highly oriented in some specific directions, which depended on the substrate temperatures. The device quality GaAs/AlN films have been obtained for the structure of Schottky-like diode. The ideality factor from the I-V measurement is 1.39. From the Hall measurements, the mobility of 3490cm2/V.s at the doping level of 2 x 1017cm-3 for GaAs films on AlN has been shown. For thermal properties of AlN films, thermal conductivity was measured with photothermal deflection spectroscopy. It was found that the thermal conductivity of AlN/Glass with 20μm of AlN films thickness was 1.798Wcm-1K-1 while the thermal conductivity of AlN/Glass with 10μm of AlN films thickness was 1.383W cm-1K-1