Study Of SiN_x Passivation On The Surface Properties Of InGaAs Photo-detectors

The dark current is the main parameter of the performance of photo-detectors. For mesa extended InxGa1-xAs infrared detectors, surface recombination current is one of significant component of dark current. We investigate surface passivation effects of SiNx films deposited by inductive coupled plasma chemical vapor deposition (ICPCVD) and plasma enhanced chemical vapor deposition (PECVD) technologies for InAlAs/InGaAs/InP photo-detectors. C-V, PL, XPS results indentify the impact of SiNx passivation on surface defect of detectors, further more TCAD simulation and first principles calculation make clear the physical origin of the change of the surface leakage current along with the technological conditions, these results provide theoretical and experimental basis to optimize the properties of infrared detector. The main results are as follows:1. We investigate surface passivation effects of SiNx films deposited by ICPCVD and PECVD technologies for InxAl1-xAs/InxGa1-xAs/InP photo-detectors. It is seen that the dark current of detectors with ICPCVD deposited SiNx film is significantly improved comparing to that using PECVD deposited SiNx film. The leakage reduction is about 4 times of magnitude at reverse bias VR=-0.5V. In order to investigate surface property of InAlAs, we use ICPCVD and PECVD technologies to deposit SiNx film for Au/SiNx/In0.83Al0.17As Metal-Insulator-Semiconductor (MIS) capacitors. By comparing C-V results, it is found that the fast and slow traps of ICPCVD deposited InAlAs surface are smaller than PECVD deposited one. From XPS results, it is suggested that the N dangling bonds at InAlAs surface are suppressed by ICPCVD technology. ICPCVD deposited device show the superior interface performance and passivation effect.2. We investigate three groups of N2/SiH4 gas flow ratio on the characteristics of deposited detectors. By comparing PL and XPS results, it is found that with the increase of N2/SiH4 gas flow ratio, radiative recombination in SiNx film increases. However the content of N-Al bond at InAlAs surface increases with the increase in N content in the SiNx films. Further more first principles calculation was usd to calculate the binding energy of N with In and Al dangling bond, it is suggested that the high density binding of N with Al dangling bonds at SiNx/InAlAs interface could be related to the interface trap reduction in ICPCVD deposited SiNx films. It is suggested that when N2/SiH4 gas flow ratio is 1.55, the dark current of InGaAs detector is lowest.