Abstract
We using the InGaAs PIN epi-wafer to realize the NIR photodiode, it has high responsivity and low dark current with large aperture size. We find that secondary diffusion after passivation would decrease the dark current, the dark current is lower dependence on radius than single diffusion, and the activation energy is more closed to ideality than single diffusion. We has two types for anti-reflection coating on photodiode, typically, the double layer ARC which combine with dielectrics, another one, depositing a TCO film on P+ InP surface, we hope that would improve lateral effect. For dielectrics type ARC, it has very low reflectivity at IR region (especially 1300~1600 less than 1%), the peak responsivity of photodiode with this ARC was 1.082 A/W at 1550nm and 0.98 A/W at 1312nm. The reflectivity of another one isn’t better than dielectrics (the reflectivity at IR about 3~7%), we need a conductive path to improve lateral effect at high power illumination. Although the peak value of responsivity with TCO film was 1.01 A/W at 1550nm and 0.94 A/W at 1312nm, the responsivity decreased seriously as power increase. Because of the interface exists a barrier height between GZO and P-type InP. This problem can overcome by reverse-bias, but the low absorption at long wavelength, we apply backside double path to improve it. The improvement is obvious, the increasing of quantum efficiency from 1400- 1750 nm, especially >1700 nm. The limitation by the reduction of InGaAs absorption coefficient is serious when wavelength > 1700 nm. It has advantage to extend the detecting band.