Study On Dark Current Mechanism Of Extended Wavelength In_xGa_1-xAs/InP Infrared Detector

As photodetectors (PDs) which cover the short-wavelength infrared (1-3 u m) range are of great importance due to their many important applications, earth observation, atmospheric exploration, night vision, etc.But with the increasing of the Indium’s content, the dark current of the detector is also increased dramatically and the performance of the detector is decreased significantly.In this paper, the Ⅰ-Ⅴ characteristics and deep level defects of the extended wavelength infrared detectors have been studied. The dark current of the detector have been simulated by the 2D-TCAD simulation software. So the dark current physical mechanisms and key parameters of the detector have been determined from the experiments and theories. It is provided the experimental and theoretical basis for the performance’increasing of the detector.The main results have:l.The extended wavelength infrared detectors grown by the MOCVD and GSMBE have been analysed.The Ⅰ-Ⅴ characteristics curves under different temperature conditions of the detector have been detected. The dark current exhibits thermal excitation characteristics at the low voltage condition and relates to the tunneling effect at the high voltage condition.2.The deep level trap of the Ino.78Gao.22As and In0.83Ga0.17As detector have been analysed by the DLTS.The two deep level traps which have the trap density of 1.4×1014cm-3 and 3.5×1014cm-3 near the middle of band gap are discovered. The high concentration of these defects could affect the performance of the device.3. With the structural characteristics and the defect information of the detector,the dark current models have been built. Ⅰ-Ⅴ curves at different temperatures are simulated by the Silvaco-TCAD software, the experimental results are agreed well with the simulated results. From the dark current simulation, Shockley-Read Hall(SRH) current and trap-assisted tunneling (TAT) current related to the deep-level trap are the main contribution to the dark current at the low voltage condition; while the band-to-band tunneling (BTBT) current is the main contribution at the high voltage condition. In addiation,the relationship between the dark current and the trap density is also detectored by the dark current model built by the Silvaco-TCAD software.4. The Ⅰ-Ⅴ curves of extended wavelength In0.83Ga0.17As detector which have the different surface passivation technology(ICPCVD,PECVD) have been analysed.It is found that the ICPCVD technology can Significantly reduce the dark current of the detector. In the low-field condition,the surface recombination current of the detector used the ICPCVD technology is lower two orders of magnitude than the detecter used the PECVD technology.