Electrical characteristics of Al/AlGaAs/GaAs diode with high-Al concentration at the interface

In this study, GaAs-based Schottky diode is fabricated by Al metal contact and Al0.95Ga0.5As interface layer. Thin film layer is epitaxially grown on GaAs with high ratio of Al in the composition. Compositional, crystallographic structure and surface of the film layer are investigated by in situ reflectance, X-ray diffraction and SEM measurements, respectively. The diode is characterized by room-temperature current–voltage (I- V ) measurements under continuous illumination and also transient illumination condition with different intensities in the range of 20–100 mW/cm2. Under bias, the diode shows single Schottky diode characteristics with about two-order rectifying behavior at dark and slight increase in rectification behavior is observed by increasing illumination intensity. Experimental dark and illuminated I- V curves are formulated by traditional thermionic emission model and the resulting forward biased semi-logarithmic I- V relations are analyzed to get insight into ideality and barrier height formation. Dark ideality factor and barrier height values are calculated as about 2.32 and 0.64 eV, respectively. Deviation from diode ideality increases with illumination is observed whereas there is a decrease in barrier height of the junction. Saturation from ideal I- V characteristics at high forward bias region is dominated by resistance effect. At this region, series resistance values are evaluated by Cheung’s theory. Additionally, switch on/off light response of the diode is observed from transient photo-current measurements for various illumination intensities. Both carrier generation under illumination and trapping mechanism at dark exhibit photo-sensitivity characteristic of the diode. As a result, increase in current flow together with improvement in rectifying behavior with illumination indicates that the diode can be adapted in opto-electronics applications.