Suppression of dark current in germanium-tin on silicon p-i-n photodiode by a silicon surface passivation technique

• Published in: Optics express 2015-07, Vol.23 (14), p.18611-18619
• Main Authors: Dong, Yuan, Wang, Wei, Lei, Dian, Gong, Xiao, Zhou, Qian, Lee, Shuh Ying, Loke, Wan Khai, Yoon, Soon-Fatt, Tok, Eng Soon, Liang, Gengchiau, Yeo, Yee-Chia
• Format: Article
• Language: English
• ISSN: 1094-4087; 1094-4087
• DOI: 10.1364/OE.23.018611

We demonstrate that a complementary metal-oxide-semiconductor (CMOS) compatible silicon (Si) surface passivation technique effectively suppress the dark current originating from the mesa sidewall of the Ge(0.95)Sn(0.05) on Si (Ge(0.95)Sn(0.05)/Si) p-i-n photodiode. Current-voltage (I-V) characteristics show that the sidewall surface passivation technique could reduce the surface leakage current density (Jsurf) of the photodiode by ~100 times. A low dark current density (Jdark) of 0.073 A/cm(2) at a bias voltage of -1 V is achieved, which is among the lowest reported values for Ge(1-x)Sn(x)/Si p-i-n photodiodes. Temperature-dependent I-V measurement is performed for the Si-passivated and non-passivated photodiodes, from which the activation energies of dark current are extracted to be 0.304 eV and 0.142 eV, respectively. In addition, the optical responsivity of the Ge(0.95)Sn(0.05)/Si p-i-n photodiodes to light signals with wavelengths ranging from 1510 nm to 1877 nm is reported.