Dynamics of AlGaN based detectors in the deep-UV

• Published in: Solid-state electronics 2008-05, Vol.52 (5), p.795-800
• Main Authors: Mazzeo, G., Reverchon, J.-L., Conte, G., Dussaigne, A., Duboz, J.-Y.
• Format: Article
• Language: English
• Subjects: AlGaN devices; Applied sciences; Compound structure devices; Diodes; Dynamic response; Electronics; Exact sciences and technology; General equipment and techniques; Instruments, apparatus, components and techniques common to several branches of physics and astronomy; MSM structures; Optoelectronic devices; Physics; Schottky photodiodes; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing; UV detectors
• ISSN: 0038-1101; 1879-2405
• DOI: 10.1016/j.sse.2007.11.014

The photoconductive dynamic response of AlGaN based UV detectors to 193 nm excimer laser radiation is presented. Two different devices have been realized, tested and compared: a metal–semiconductor–metal (MSM) planar structure and a Schottky diode. The capability of these devices to detect the emission of a nanosecond pulsed excimer laser is proven and the decay time and dependency on the beam’s density of energy evaluated. The transient response of the MSM device closely follows the laser pulse, with a photoconductive decay time shorter than 3 ns. On the contrary, the Schottky diode shows a slower photoconductive rise and decay kinetics due to the material series resistance coupled with the junction capacitance. Moreover, a longer time constant tail is also evident in this case with a characteristic decay time of about 40 ns, due to the presence of trap states localized at 0.2–0.3 eV from the band edge. The detection dynamics has been evaluated by changing the beam intensity between 2 × 10 −5 and 0.2 mJ/mm 2. The signal increases linearly in the case of the MSM device up to 0.002 mJ/mm 2 whereas, for a further intensity rise, the response becomes prone to a sub-linear behavior. On the contrary, the Schottky diode showed a linear trend below 2 × 10 −2 mJ/mm 2.