Ge on Si and InP/InGaAs single photon avalanche diodes

Abstract

This paper describes single photon detection for Ge on Si separate-absorption-charge-multiplication (SACM) avalanche photodiodes and advances in quenching for InP/InGaAs single photon avalanche diodes. INTRODUCTIONApplications for single photon avalanche diodes (SPADs) in the wavelength range of 1.0-1.6 μm include optical time domain reflectometry [1], quantum key distribution (QKD) [2], laser ranging [3], three-dimensional imaging [4, 5], and time resolved spectroscopy [6]. Excellent single photon detection performance has been reported for InGa 0.53 As 0.47 /InP avalanche photodiodes (APDs) [4-9]. For example, Hu et al. have reported single photon detection efficiency (SPDE) of 30% with dark count probability of 1 10 -5 at 230K at 1.31 μm [8], while Itzler et al. have shown a similar result. They reported SPDE of ~ 20% with dark count rate of a few kHz with moderate cooling [9]. Recently, at an operation wavelength of 1.55 μm, Tosi et al. have reported dark count rate as low as 400 s -1 with SPDE of 28% at 175K [10]. Si SPADs have exhibited high detection efficiency and low dark count probability [11][12][13], however, the band gap of Si restricts operation to wavelengths < 1 μm. One approach to extend the operating wavelength of Si-based SPADs is to utilize a separate absorption, charge, and multiplication (SACM) APD structure in which the multiplication region is Si with adjacent InGaAs [14] or Ge absorption regions [15]. The use of Si for the multiplication region is advantageous owing to its low excess noise factor and favorable avalanche breakdown probability. The benefits of Ge as the absorber include its compatibility with CMOS process technology and its long-wavelength cutoff (λ ~ 1.55 μm). An advantage of Si-based SPADs is that they can be integrated with CMOS circuits [12,16], which facilitates performance improvements in applications such as photon timing and monolithic focal plane array imaging. The challenge presented by Ge on Si for single photon detection is the relatively high dark current that results from the lattice mismatch between Ge and Si. This leads to high dark count rate (DCR). Recently, improved epitaxial growth techniques have enabled significant progress in the performance of Ge on Si APDs [15,17,18]. In this paper, we report Geiger-mode operation, i.e. single photon detection, of Ge on Si SACM APDs.InGaAs/InP single photon avalanche diodes (SPADs) have achieved high SPDE and low DCR in the near-infrared wavelength range between 1.0 and 1.7 μm with moderate cooling [19,20]. However, afterpulsing is a significant performance limitation for infrared SPADs, especially in high-speed applications. During an avalanche event, the current that flows through the diode will fill some of the deep level traps in the high-field multiplication region. These traps release carriers after the avalanche current is quenched. If these carriers are released during subsequent detection windows, they will give rise to excess dark counts. The release rate of the carriers from the traps is proportional to t...