Broadband visible-to-telecom wavelength germanium quantum dot photodetectors

Germanium (Ge) quantum dot (QD) photodetectors (PDs) were fabricated on Ge substrates exhibiting a broadband, visible to near-infrared (near-IR) photoresponse in the lambda = 400-1550 nm range. Room-temperature responsivities (R-sp) up to 1.12 A/W and internal quantum efficiency IQE = 313% were obtained, superior to conventional silicon and germanium photodiodes. Noise analysis was performed at visible lambda = 640 nm and telecom lambda = 1550 nm wavelengths, both yielding room-temperature specific detectivity D* similar or equal to 2 x 10(10) cm Hz(1/2) W-1. Lowering the operating temperature and incident power led to sharply enhanced performance, with D * = 1.1 x 10(12) cm Hz(1/2) W-1 and IQE = 1000% at T = 100 K for an incident power of 10 nW at lambda = 1550 nm. Based on their simple fabrication and silicon technology compatibility, these Ge QD PDs represent a promising alternative for broadband, high-performance visible to near-IR detection. Published by AIP Publishing.