Systematic Study on Aluminum Composition Nonuniformity in Aluminum Gallium Nitride Metal-Semiconductor Metal Photodetectors

The influence of aluminum composition (Al%) nonuniformity on AlGaN metal-semiconductor-metal photodetectors was thoroughly studied on a device level. The Al% fluctuation was precisely measured by X-ray photoelectron spectroscopy and mapped by energy dispersive spectrometry; the dislocation density was investigated by X-ray diffraction rocking curve. Both theoretical simulation and experimental testing showed a significant difference in the responsivity, dark current, and decay time in the device with different Al%. The Al% fluctuation is also a likely cause of the long decay time of the device.