Ultra‐Sensitive Cubic‐ITO/Silicon Photodiode via Interface Engineering of Native SiO_x and Lattice‐Strain‐Assisted Atomic Oxidation

Abstract

A highly orientated cubic indium tin oxide (c‐ITO)/native SiOx/n‐Si Schottky photodiode with negligible electronic noise is demonstrated. This extraordinary property is achieved via simple interface engineering, which combines native SiOx, facile air‐annealing, and the resulting ITO‐lattice‐strain‐assisted oxidation of proximal underlying Si atoms. An exceptionally well‐passivated ITO/n‐Si interface is realized, which leads to a heretofore unreported single‐atom‐thin inversion layer observed via transmission electron microscopy imaging. The device exhibits a record‐low dark current density of ≈3 × 10–8 A cm–2 at −5 V, a tenfold reduction over the lowest reported value. Additional excellent optoelectronic properties achieved include self‐powered operation, high quantum efficiency, fast time response, and ultra‐high sensitivity for low illumination signals. Interface characterization reveals that ITO‐lattice relaxation and oxygen diffusion during annealing create a highly ordered c‐ITO crystal and an extended ≈2.2 nm SiOx interlayer formed via atomic oxidation of the underlying pristine Si, thus rendering a high‐quality interface. Moreover, the Schottky barrier is further enhanced by the presence of negatively charged sub‐stoichiometric silicon oxide interlayer. These results bring forth new insights in the surface atomic oxidation process and the significance of natively grown SiOx which together contribute to the realization of economic highly sensitive photodetectors.

Analog Tunnel Memory Based on Programmable Metallization for Passive Neuromorphic Circuits

“…Interestingly, during the reactive sputtering of the MPL, energetic oxygen atoms bombard into native SiO x and additionally oxidize a few layers of Si atoms in the immediate proximity of the native SiO x /p ++ -Si interface. This is confirmed by the increased oxide thickness (∼4.7 nm; Figure f) and a greater brightness contrast against the pristine SiO x layer, which is attributable to strong negative charging during the plasma oxidation . As illustrated in Figure g, the atomic oxidation of the underlying Si atoms contribute to the creation of a high-quality interface where extant defects are either minimized or eliminated by the advancing SiO x –Si interface, which plays an important role for excellent tunneling behaviors in the PM-ATM, as discussed below.…”

Facilely Achieved Self‐Biased Black Silicon Heterojunction Photodiode with Broadband Quantum Efficiency Approaching 100%

“…The wide depletion region (space charge region) and the electric field tailing region (weak field region) in this device serve to rapidly sweep and effectively extract the charge carriers. Additionally, the strong near‐surface electric field strength induced by the Schottky contact, and the proper interfacial chemical passivation effect associated with the native‐oxide‐based air‐annealing process, [ 22 ] remarkably mitigate photocarrier loss to surface recombination. Cross‐sectional SEM images for bare nanostalagmite structures are shown in Figure 1f (low magnification) and Figure 1g (high magnification).…”

“…Notably, during annealing in the air, oxygen diffuses into the Si sub‐surface, thereby oxidizing a few atomic layers of Si and creating a high‐quality interface between the nc ‐ITO and underlying SiO x ‐Si. [ 22 ] This interfacial oxidation is examined in the sidewall region as shown in Figure 2g: ≈2 nm SiO x is grown between the nc ‐ITO and nanostalagmite. The presented TEM image reveals that the native oxide attaches to the textured surface conformally.…”

“…A high‐quality interface is achieved via a combination of the contact‐induced surface electric field and the native Si oxide chemical passivation, which together effectively preclude the need for elaborate fabrication processes. [ 22 ] Only basic technologies are utilized to produce the single contact b ‐Si photodiode. From 570 to 925 nm wavelengths, the self‐biased heterojunction photodiode exhibits average broadband EQE of greater than ≈98%; and, from 500 to 960 nm, the overall EQE is over ≈95%.…”

Rational Approach for High‐Efficiency Dopant‐Free Solar Cells Characterized with Key Parameters

“…[ 112–133 ] d) Measured Schottky barrier heights of different TCOs, CBMs, and TMOs. [ 134–141 ] X‐ray photoelectron spectroscopy (XPS) spectra of e) nondoped, f) V‐doped, and g) Nb‐doped MoO 3− x films. Reproduced with permission.…”