Photodetection in Hybrid Single-Layer Graphene/Fully Coherent Germanium Island Nanostructures Selectively Grown on Silicon Nanotip Patterns

Abstract

Dislocation networks are one of the most principle sources deteriorating the performances of devices based on lattice-mismatched heteroepitaxial systems. We demonstrate here a technique enabling fully coherent Ge islands selectively grown on nano-tip patterned Si (001) substrates. The Si-tip patterned substrate, fabricated by complementary metal-oxidesemiconductor (CMOS) compatible nanotechnology, features ~50 nm wide Si areas emerging from a SiO 2 matrix and arranged in an ordered lattice. Molecular beam epitaxy (MBE) growths result in Ge nano-islands with high selectivity and having homogeneous shape and size. The ~850°C growth temperature required for ensuring selective growth has been shown to lead to the formation of Ge islands of high crystalline quality without extensive Si intermixing (with 91 at.% Ge). Nano-tip patterned wafers result in geometric, kinetic diffusion barrier intermixing hindrance confining the major intermixing to the pedestal region of Ge islands where kinetic diffusion barriers are however high. Theoretical calculations suggest that the thin SiGe layer at the interface plays nevertheless a significant role in realizing our fully coherent Ge nano-islands free from extended defects especially dislocations. Single layer graphene (SLG)/Ge/Si-tip Schottky junctions were fabricated and thanks to the absence of extended defect in Ge islands, they demonstrate high performance photodetection characteristics with responsivity and I on /I off ratio of ~45 mA/W and ~10 3 , respectively.

Camphor-Based CVD Bilayer Graphene/Si Heterostructures for Self-Powered and Broadband Photodetection

“…Therefore, the dark current under a low reverse bias (from 0 V to −2 V) is much lower than under a low forward bias (form 0 V to +2 V), as shown in Figure 4 b,c. It is noteworthy that the SBH tunable behavior of the camphor-based CVD graphene/p-Si heterostructure is consistent with the numerous study results of the conventional CVD bilayer graphene/Si heterostructures reported previously [ 58 , 59 , 60 , 61 , 62 , 63 ].…”

Dislocation-Free SiGe/Si Heterostructures

“…However, notice that it can be straightforwardly used to investigate realistic shapes as shown in Refs. [37][38][39].…”

“…However, notice that it can be straightforwardly used to investigate realistic shapes as shown in Refs. [37][38][39]. Following the work in [35], the typical elastic field of VHEs as in Figure 7a can be computed by FEM calculations and it is illustrated in Figure 7b for a pure Ge epilayer by means of the hydrostatic stress .…”

High‐Responsivity Near‐Infrared Photodetector Using Gate‐Modulated Graphene/Germanium Schottky Junction

“…Zeng et al reported a monolayer graphene/Ge Schottky junction based IR photodetector with a higher operation speed . Niu et al also reported a high‐performance IR photodetector based on a monolayer graphene/Ge island/Si nanotip structure by growing the dislocation‐free Ge islands on a Si nanotip substrate . In these cases, the best responsivity was ≈62 mA W −1 , which is still substantially lower than the commercially available Ge IR detectors (responsivity ≈0.8 A W −1 with 1–100 µA cm −2 of dark current).…”